The Best Humidifier

After having a former National Oceanic and Atmospheric Administration (NOAA) scientist test eight top-ranked humidifiers, we’ve found that the Honeywell HCM-350 is the best humidifier for most people. It’s the easiest to fill and clean, which are the two things you’ll be doing the most with any humidifier you buy. Unlike nearly every other humidifier, the HCM-350 is designed so that every part that touches water is free of electronic components and sharp angles, and is completely submersible (and dishwasher safe) for easy scrubbing. What’s more, it is the only humidifier we found that has a reservoir made from a single, continuous piece of plastic, preventing leaks, which are a common source of poor user reviews for most other humidifiers.

Last Updated: November 20, 2015
This fall we tested eight new humidifier models against our existing picks. The result? We’re sticking with those picks, for their superior performance, ease of maintenance, and cost-efficiency. Our main pick remains the Honeywell HCM-350, and the runner-up remains the similar Sunpentown 9210. For big rooms, we like the SPT SU-4210. Our upgrade model, the Venta Airwasher LW25, is more expensive, but doesn’t require daily cleaning. At readers’ request, we've added a warm-mist pick too. The Vicks V750 is more solidly built and stays cooler to the touch than competing models. Overall, we prefer evaporative cool mist humidifiers—they're more energy efficient and have no hot parts—some people like warm mist, and Vicks delivers an impressive amount. Look for our full guide update before the end of the year.
Expand Most Recent Updates
November 10, 2015: In response to reader requests, we've added a warm-mist pick to this fall's updated humidifiers guide. The Vicks V750 is more solidly built and stays cooler to the touch than competing models, and delivers an impressive amount of vapor. While overall we prefer evaporative, "cool mist" humidifiers—they're significantly more energy efficient and have no hot parts at all—some people like the feeling of warm mist, and the Vicks delivers it reliably. All of our other picks will remain the same. Look for an update to our humidifiers guide later this month.
January 16, 2015: A former NOAA scientist tested eight top-ranked humidifiers and found that the Honeywell HCM-350 is the best humidifier for most people. It’s the easiest to fill and clean (the two things you'll do most with it) and unlike practically every other humidifier, any part that touches water is free from electronic components, so it’s dishwasher safe. Plus, it’s the only humidifier made from a single piece of plastic, meaning leaks are much less likely.
November 18, 2014: After having a former NOAA scientist test eight of the top-ranked humidifiers around, we've found that the Honeywell Germ Free Cool Mist Humidifier is the best humidifier for most people. It's very quiet (though not silent), and has a 1-gallon reservoir that's dishwasher safe because it's constructed from a single piece of plastic. That means it's virtually leakproof. In the past, we've recommended ultrasonic models because they are almost totally silent, but after further head-to-head testing, it's clear that evaporative humidifiers are a better value. Yes, they emit a bit of noise, but like a very quiet fan, it's far quieter than what anyone would consider to be objectionable. Also, the cost of consumables is lower and there's no chance of running into the annoying white dust effect. We aim to have all of our research and testing that led us to this decision published in the next few weeks.
November 14, 2014: Consumer Reports recently updated their ratings of humidifiers (subscription required) and some of the models mentioned below saw a change in their rating from last year (the Air-O-Swiss score remained the same, while our step-down from STP went from a score of 82 to 86). We've updated the scores in the guide below. We're in the middle of researching and testing new models, and will post the results as soon as we are able.
February 18, 2014: We tested the Venta LW25 Airwasher and found that while it was as good as our pick at humidifying spaces, at $300, it's still more expensive, and it's still louder because it's an evaporative humidifier that relies on air circulation to move and moisten air. We like it as a step up, but it's not the best for most people.
January 21, 2014: We're currently testing new models, so this guide is set to wait status while we determine if we need a new pick in this category.
October 4, 2013: We took a look at Consumer Reports' newest humidifier rankings (subscription required), but not much has changed: Our pick received 84 points, second only to Crane's series of whimsically-designed humidifiers (cows, Hello Kitty, pandas...). Vick has released three new humidifiers, the V6400, V750 and V3700M-V, all of which have small, one-gallon tanks, and no other features we're particularly excited about. We'll keep an eye on the possibly-in-the-works Dyson humidifier, but for now, our picks stand.
Honeywell Germ Free Cool Mist Humidifier, HCM-350
This machine combines solid performance with a virtually leakproof, dishwasher-safe reservoir. It’s the easiest to fill and clean, too. It's best for spaces less than 400 square feet.

*At the time of publishing, the price was $70.

We tested the humidifiers in a climate-controlled space while regularly logging the temperature, humidity, and particle count (where applicable). Then we evaluated them for ease of use and cleaning, which was just as important as humidifying power. It’s hard to overstate how annoying it can be to clean most humidifiers being sold today, which is unfortunate because regular cleaning is essential to achieving optimal (and safe) performance. A typical humidifier is full of nooks and crannies that funky stuff loves to grow in. Because some of those dirty parts house the electronics, they can be even more difficult to clean than usual. As such, the fact that the Honeywell is specifically designed to avoid those issues and make cleaning easy is a huge deal.

The Honeywell uses evaporative technology (as opposed to ultrasonic or warm mist), which means you will never run into issues with white dust, pools of water around the base, or over-humidification. While it doesn’t have the horsepower to take a living room from bone-dry to subtropical in 30 minutes, it can get a large bedroom or medium-size living room up to a comfortable level of humidity in less than two hours, and keep it there.

Also Great

*At the time of publishing, the price was $72.

Sunpentown SU-9210 Digital Evaporative Humidifier
This costs a bit more than our pick and doesn’t have a one-piece reservoir, but it offers comparable performance should our pick go out of stock.

As it has been the number one best-selling humidifier on Amazon for quite some time, it’s unlikely that the Honeywell will become unavailable. But if it does, or if it’s sold out, the Sunpentown 9210 is our runner-up pick. It performs very similarly to the Honeywell, and is easy to clean because it also has no electronic components inside that can touch water, and it even adds a humidistat (which is accurate according to our testing). However, it’s a bit more expensive up front, has annoying beeping buttons, and does not have a one-piece reservoir, which could lead to leaks in the long run.

Like the Honeywell, its evaporative humidifying mechanism doesn’t have the same horsepower as an ultrasonic model. When you start pushing 350 square feet or larger, you’re going to have a tougher time getting a comfortable level of humidity with an evaporative humidifier. If you’re willing to deal with more maintenance, it might just be worth going for an ultrasonic model instead, but in our experiences (having owned both types), we’d rather have a slightly under-humidified room and less maintenance.

Also Great
SPT SU-4010 Ultrasonic Dual-Mist Warm/Cool Humidifier with Ion Exchange Filter
Ultrasonic humidifiers are silent and humidify at a faster rate than our pick, but can over-humidify if you’re not careful. This one performs similarly to models costing twice as much. It's good for a space 400 square feet or larger.

In the past we’ve recommended ultrasonic models because they are almost silent as opposed to just “really quiet.” But after further head-to-head testing, it’s clear that evaporative humidifiers are a better value for most people, which is why we have changed our main pick.

Ultrasonic models can cause an annoying white-dust effect, and they can over-humidify the room. Evaporative humidifiers solve those problems by design, but they’re not as powerful. Still, if your bedroom is particularly large (around 400 square feet or larger), you might consider trading off easier cleaning for a more powerful ultrasonic model. In that case, the Sunpentown SPT-4010 (the runner-up from last year’s guide) is our pick for best ultrasonic humidifier. Its output is comparable to that of the class-leading Air-O-Swiss 7135 we previously recommended, but it costs about half as much. It doesn’t have a humidistat, but in this year’s testing, the one in the Air-O-Swiss was wildly inaccurate, so that’s a wash anyway. However, it’s a pain to clean because the water tray is full of sharp angles—a shared trait among all the ultrasonic humidifiers we looked at.

Step Up
Venta LW25 Airwasher
This needs to be refilled only every 10 days compared with the daily refills required by our other picks. Whether that’s worth an extra $240 is up to you.

We’d also like to shout out the Venta Airwasher LW25. For $300 (sometimes lower depending on where you buy it), you get an extremely efficient evaporative humidifier that needs to be refilled only once every 10 days compared with the daily refills required by our other recommendations. Its high upfront cost is somewhat mitigated by its extreme energy efficiency in the long run, but it is still very expensive. Venta recommends rinsing every two weeks with its Venta Water Treatment Additive to remove minerals, and thoroughly cleaning every six months with its Venta Cleaner, so running costs aren’t as low as they could be.

Table of contents

Who am I to talk about humidifiers?

My name is John Holecek, MS, and I’ve been involved in climate research since 1999. I’ve studied atmospheric physics and chemistry in locations ranging from the Continental US, to the Arctic, to the remote island nation of the Maldives. These field campaigns were government-sponsored research programs aiming to improve our understanding of Earth’s climate.

Over the past four months, I’ve read scientific literature on the health effects of humidifiers, surveyed existing products, reviewed the sparse existing product reviews, and tested eight select models.

In order to test these models in a climate-controlled space, we threw two de-humidifiers, a portable A/C unit, and a 1,500-watt heater at my office. To evaluate the humidifiers, we used two portable temperature and humidity data loggers, and a laboratory-grade particle counter to size up the air washers (read more below in How we tested).

What is humidified air?

You might be surprised to learn that the warm air in your home that feels so dry is not actually any drier than the cold air outside. It just feels drier because as air gets warmer, more moisture is needed to saturate it. So while absolute humidity (the total amount of moisture in the air) doesn’t change between your home and the outside air, relative humidity (which is what you feel) decreases dramatically when you artificially heat your home. The warmer the air, the more humidity is needed to maintain a comfortable level of relative humidity.

Humidified air is just air that has had moisture artificially added to it in order to maintain a comfortable degree of relative humidity. According to the Mayo Clinic, you’ll want to keep the relative humidity levels in your home somewhere between 30 and 50 percent. Any lower than 30 percent and your environment will become prone to all of the unpleasant side effects associated with dry air we talked about earlier. But don’t overdo it “just to be safe,” because if you go over 50 percent, you run the risk of attracting mold and bacteria growth.

Who is this for?

If you are bothered by any of the symptoms caused by dry air, such as dry sinuses, nose bleeds, cracked and sore lips, or shocks from static electricity, then the air in your home is likely too dry. Getting a humidifier would help ease these symptoms. On the other hand, if you notice condensation routinely forming on the inside of your windows, or frequently find yourself having to clean mold off of your walls or window frames, your home is too humid, so you don’t need a humidifier.

If you want to be certain that humidity is the culprit, you can get a hygrometer on Amazon for $9 (or a hardware store for about $20) and see if your home’s air is under the recommended 30 to 50 percent relative humidity range.

A portable humidifier, like the ones we researched here, is the cheapest and easiest way to humidify your home without needing to deal with an HVAC contractor. However, humidifying your home with one of these is not as simple as buying one of our picks and filling it with water. If you don’t take care to use and maintain it properly, a humidifier can do more harm than good1. Indeed, the Mayo Clinic warns that, “Although useful, humidifiers can actually make you sick if they aren’t maintained properly or if humidity levels stay too high. If you use humidifiers, be sure to monitor humidity levels and keep your humidifier clean.”

If you know you’re not up for this level of regular maintenance and cleaning, you’re better off investing in a whole-house humidifier system linked into your forced-air furnace, or skipping humidifiers entirely.

Most humidifiers require regular maintenance, refilling with water daily and doing a thorough cleaning every one to three days. There are exceptions, like our step up, but be honest with yourself. If you know you’re not up for this level of regular cleaning and maintenance, you’re better off investing in a whole-house humidifier system linked into your forced-air furnace, or skipping humidifiers entirely (consult a local HVAC contractor for more details). Otherwise, you may end up with a breeding ground for germs. We talk in more detail later on about the potential complications that can stem from poor maintenance, but none of that will be a problem so long as you follow the directions.

How we picked

This is the third year we’ve done this guide, so we went into it with some prior knowledge of good sources of reviews and information and what to look for. Once again, we researched popular models on Amazon, reviewed the latest testing from Consumer Reports, consulted Allergy Buyer’s Club, Top Ten Reviews, Best Buy, and ConsumerSearch, and we also read the comments from our previous guide for feedback and suggestions from our readers.

This year again, we focused on portable models that work either on the floor2 or a table/dresser because they can be easily added to any environment with no need for installation, and can be moved around as needed. These midsize units are recommended for rooms between 200 and 700 square feet, which is more than enough coverage for an average bedroom3 (which is primarily where these are used), and plenty for most larger rooms in most homes. While there are large console units capable of humidifying an entire floor of a home, we didn’t consider them for this round of testing because at that point, you’re better off installing something directly into your HVAC system. A standalone unit would likely over-humidify some rooms while under-humidifying others.

We looked for units that were be powerful enough to humidify 200 to 700 square feet overnight, and reservoirs large enough to make it through the night without being so big that they are awkward to fill in your sink or overwhelm a dresser or table.

There’s also the question of what kind of humidifier to get because different technologies have different pros and cons.

In the past, we had primarily recommended ultrasonic humidifiers because they are nearly silent and capable of outputting moisture at a higher rate than humidifiers based on other non-heated technologies. This leads to higher scores in independent testing conducted by Consumer Reports (subscription required) and other publications because noise and rate of output are valued highly when it comes to quantitative testing. But these same traits that benefit ultrasonic humidifiers in lab testing can actually lead to problems in the real world.

Ultrasonic humidifiers rely on a vibrating diaphragm to generate vapor independent of the surrounding relative humidity, which is why they’re so fast. But if you’re not using distilled water (which gets expensive very quickly), or if the included demineralization treatments prove to be ineffective (a common complaint), this can cause a fine white mineral dust to settle all over the surrounding area, which is no good.

And while fast humidification is a good thing for a dry house, if your house is already comfortably humidified because you’ve been running the machine for a while, continuing to humidify will lead to over-humidification very quickly. This can cause issues with mold growth and other undesirable side effects.

Some models include humidistats to prevent this, but these are hardly foolproof. Indeed, two out of the four humidistat-equipped machines we tested failed to provide accurate readings—discrepancies as large as 43 percent were observed for the Sunpentown SU-3600 and greater than 10 percent for the highly touted Air-O-Swiss 7135. Also, if there’s no water in the tank to absorb the vibrations, the machine can actually break itself—which is why we looked only at ultrasonic models that had an auto-off feature.

Finally, if you forget to clean, then whatever’s growing in the reservoir will also be vaporized and enter your house’s air. Overall, these are substantial downsides that lab testing fails to account for, and led us to look more deeply into competing technologies this time around.

Previously, we had written off evaporative humidifiers because they are louder and slower to humidify a space than their ultrasonic counterparts, but readers (rightly) called us out for not giving more weight to the upsides of evaporative technology.

Evaporative humidifiers utilize the natural process of evaporation to add moisture to the air. Dry air is drawn in and passed through a wet wicking filter, and humidified air is blown out into the room by a fan. They do make more noise than some due to the fan, but it’s not objectionable—far less than, say, an air conditioner or air purifier. The evaporative process is also slower than the vaporization process used by ultrasonic models, but it does prevent over-humidification because the process stops functioning before the air can get too wet. Also, while high output is desirable at first, if you’re continuously running your humidifier, it’s really not necessary for simply maintaining an already comfortable level of humidity.

Evaporative models are also among the cleanest because any minerals are left behind, trapped in the wicking filter. The wick filters do need to be replaced, or at least cleaned, every one to three months, but if you leave it a bit too long, the penalties are trivial—basically just reduced efficiency, but no white dust, no vaporized bacteria. Over time, the cost of wick filters (about $12 each) is comparable to the cost of demineralization filters, but the initial purchase price tends to be lower. You can buy a decent evaporative model for about $50 whereas quality ultrasonic models start around $70.

The other technology worth considering is referred to as “air-washing” by marketing materials, but it’s really just a variation on evaporative humidification. The difference is that instead of a stationary wick, they have a stack of very slowly rotating discs. A fan draws air into the unit, then across the wet discs where (in theory) particles are trapped in the water and humidified air is blown out. These are quieter than evaporative models, but also very expensive—a midsize model starts around $250.

The other technologies are steam (warm mist) and impeller, but they should be avoided. Steam humidifiers heat water so it releases steam. As you might have guessed, this is not terribly efficient and poses a burn hazard for children (and forgetful adults). Impeller models use a rapidly spinning disk to fling water against a diffuser plate that breaks the droplets into fine mist. They are quiet, but like the ultrasonic models can produce a white dust. The moisture output is low so they are best for small rooms (approximately 0.5 gallon per day versus 2 gallons per day for midsize models). Based on their generally abysmal user ratings on Amazon and their very low output, we skipped these models.

With that in mind, we built a list of 43 models. After paying more attention to factors like popularity, price per square foot covered, user review averages, and outside editorial reviews, we narrowed it down to eight with prices ranging from $30 for the Safety 1st (our budget pick) to a lofty $320 for the Winix Fresh Home Air Washers AW107. Five new models were brought in house for a head-to-head comparison against the previous three picks.

Evaporative models

Ultrasonic models

  • Sunpentown SU-4010 ($75, 500 square feet) Last year’s budget pick, also recommended by Consumer Reports and Consumer Search, and has 3.6 Amazon stars across 655 reviews.
  • Air-O-Swiss 7135 ($180, 650 square feet) Last year’s top pick and highly regarded by Consumer Reports and other online publications.
  • Safety 1st Ultrasonic 360 Humidifier ($30, 215 square feet) Very simple, yet effective. For rooms less than 300 square feet. Amazon user ranked 3.7 stars across 742 reviews.
  • Stadler Form Hera ($200, 600 square feet) Highly rated (4.5 stars) by Allergy Buyer’s Club, and has a large 2-gallon reservoir and good feature set, including a humidistat, demineralization cartridge, silver antimicrobial cube, and night mode.

Air washers

  • Venta LW25 Airwasher ($240, 400 square feet) Compact unit with huge 2-gallon reservoir and very quiet fan.
  • Winix FreshHome Air Washers AW107 ($320, 600 square feet) Highly rated (number 3) by Top Ten Reviews. It has auto mode to dim display and slow fan during the night. Plasmawave feature claims to purify air, but we found it to emit an irritating high-pitched noise. Unfortunately there is no switch for this feature.
We tested the machines’ maximum daily output outside.

We tested the machines’ maximum daily output outside.

For the testing process, we wanted to develop a series of questions that could be objectively addressed: humidifying ability, rate of water usage, noise level, power consumption, cost of consumables (wicks, demineralization treatments, specialized cleaning supplies). Results from these tests were combined with subjective considerations such as ease of use, filling, cleaning, simplicity of controls, durability, and overall fit and finish. We cover our methods and results in greater detail in the How we tested section later on.

Based on the results of our objective testing, plus ease of handling, consumer reviews, and a preference toward simplicity, both of the evaporative models float to the top of the heap. They have advantages of never over-humidifying and never producing a white dust, whereas users of ultrasonic models have reported seeing dust, even with demineralization cartridges. Among these two, the Honeywell had a slight edge in usability and design. After deciding on this, Sweethome editors Harry Sawyers and Ganda Suthivarakom bought the Honeywell and provided us with their own (positive) feedback.

Honeywell HCM-350 center, and from left to right, SPT SU-4010, SPT SU-9210, Venta LW25, Safety 1st.

Honeywell HCM-350 (center), and (from left) SPT SU-4010, SPT SU-9210, Venta LW25, Safety 1st.

Our pick

Honeywell Germ Free Cool Mist Humidifier, HCM-350
This machine combines solid performance with a virtually leakproof, dishwasher-safe reservoir. It’s the easiest to fill and clean, too. It's best for spaces less than 400 square feet.

*At the time of publishing, the price was $70.

The Honeywell HCM-350 is affordable and, in testing, it performed consistently well across all categories we measured. While it didn’t top the charts, it was a solid performer, raising the relative humidity of my office by 14 percentage points over the course of three hours. (More on this in a minute.) More important, among our entire test batch it was the easiest to clean and fill, which are the two things you’ll be doing most often with any humidifier. Regular cleaning is crucial for optimal humidifier efficacy and for keeping your environment healthy, so the fact that this unit makes it easy means that you’ll get better performance in the long run.

The base tray is typically the hardest part to clean in a humidifier, but this one is dishwasher safe and has no right angles where gunk can accumulate.

The base tray is typically the hardest part to clean in a humidifier, but this one is dishwasher safe and has no right angles where gunk can accumulate.

The Honeywell HCM-350’s ease of use and cleaning is the result of very deliberate design decisions on the part of the manufacturer that avoid the pain points common in other competing models. The best example of this is that all parts that touch water in the Honeywell (and are thus liable to accumulate bacterial/algal/fungal growth) contain no electronic parts and are completely submersible in water for easy washing—the reservoir and water tray are even dishwasher safe (top rack only, no detergent; the reservoir is quite tall, so most will not be able to set it upright on the top rack). This is how it should be. Yet the HCM-350 stands in stark contrast to many models, like our former Air-O-Swiss 7135 pick, which contain electronics in the base that require you to clean it by hand.

Our home and garden editor Harry Sawyers has owned several disappointing humidifiers in the past. He was particularly appreciative of the HCM-350’s tray. He calls it a huge improvement over the typical humidifier’s base unit, which has “a million nooks and crannies to clean—and a cord coming off of it.”

Our pick’s bottom tray, however, has no cords coming off of it and no nooks, so a simple sponge or scrubber is all that’s necessary to give it a thorough, manual cleaning. If necessary, it can be totally immersed without damaging the electronics or cleaned in the top rack of the dishwasher. Compare that to our ultrasonic pick, the Sunpentown SU-4010, which Sawyers also owns and has to “get in there with a vinegar-soaked toothbrush” to clean.

The reservoir is small, but has a huge filling hole for easy cleaning, and a comfortable, grippy handle for easy transportation from the sink to the machine.

The reservoir is small, but has a huge filling hole for easy cleaning, and a comfortable, grippy handle for easy transportation from the sink to the machine.

The reservoir is also fairly easy to clean thanks to a huge filling hole that you can easily stick your arm into if need be. Compare that with the Safety 1st’s tiny 1.75-inch-diameter fill hole, which is only big enough for two fingers, or the Sunpentown SU-4010, which can fit a hand, but not an arm. For the most part, simply filling with warm soapy water and giving this tank a good shake should suffice. You can place the tank in the top rack of the dishwasher, but most people will only be able to fit it in sideways, which doesn’t allow you to disinfect the inside of the tank. Since that part of the tank generally gets filled and emptied with tap water regularly, it shouldn’t get too dirty.

Another aspect we like about the reservoir is that it is the easiest to fill. Sure, its 1-gallon size means you’re going to have to fill it more often (about twice a day if you’re running it on high for 24 hours), but it fits under an average bathroom sink just fine (confirmed by all three testers). The tank’s thick, molded handle will support it while filling, so you don’t need to hold the tank in place, a feature greatly appreciated by Sweethome’s executive editor Ganda Suthivarakom. Sawyers liked that it barely dripped at all when lifted from the base.

The handle also provides comfortable transportation that all testers appreciated—this is especially useful when it’s loaded up with liquid.

The reservoir easily fits under your typical bathroom sink and the handle holds it up while you fill.

The reservoir easily fits under your typical bathroom sink and the handle holds it up while you fill.

Not only is the reservoir easy to fill and carry, it’s more durable than other models’ as well because it’s blow-molded from a single, continuous piece of plastic (think like a milk jug). This is better than the two-piece (or more) fused-plastic designs found on many other models. The one-piece design is much less likely to develop leaks over time because it doesn’t have any seams that can come apart. This means it will likely outlast its three-year warranty, which is already generous compared with most models’ one-year warranty.

Once you’ve filled the HCM-350’s reservoir, closing it is as easy as screwing the cap on tightly, dropping it into the base, and turning the three-fan speed rotary switch to the desired setting and putting it somewhere out of the way for the next 12 to 24 hours (depending on which setting you use)—compare that with the Air-O-Swiss 7135’s six-button, pictorial UI.


Admittedly, putting the Honeywell out of the way can be a bit difficult to do because of its large size—measuring 18 by 10 by 13 inches and weighing 9 pounds, it was the second-largest unit we tested. But the fact that it uses evaporative technology means you can put it on the floor behind a couch or in a corner without having to worry about puddles accumulating around the base. This is not the case with ultrasonic models.

You’ll never encounter problems with white dust.

Another benefit of the HCM-350’s evaporative design is that you’ll never encounter problems with white dust. Any minerals in the water that would be vaporized by an ultrasonic diaphragm are simply trapped in the wick, which means you can use it with plain tap water with no issues. Over time, the wick fills up and needs to be cleaned or replaced in order to restore efficiency, but at least this is a reliable means of keeping mineral dust out of your air and off of your furniture. User reviewers of ultrasonic models often complain that they get white dust even when they use the included demineralization treatments; this is one of the main reasons we switched our pick this year.

But, of course, none of this would matter if the HCM-350 didn’t also perform well in testing. While it never topped the charts, it performed consistently well in all measurable categories.

When it comes to humidifying a room, the HCM-350 is a solid performer. In our initial series of tests, it was able to raise the relative humidity of my 160-square-foot office with standard 8-foot ceilings by 14 percent (from 50 to 64 percent) over the course of our three-hour testing period.

This was right in line with the other machines of similar size and only significantly less effective than the Air-O-Swiss, which raised relative humidity by a whopping 34 percent (though it formed a massive puddle on the floor in doing so). However, it’s worth noting that evaporative humidifiers tend to underperform in already wet conditions since dry air sucks up moisture at a faster rate than humid air. We tried everything we could to lower the starting relative humidity for our scheduled testing day (bringing in multiple dehumidifiers, an air conditioner, and a space heater), but we were unsuccessful.

After an initial delay of several days of uncooperative weather, we had to make do with the best we could to get this guide done in a timely manner. But just to make sure, we conducted another test on a much later, drier day in a slightly smaller room (120 square feet). Under these conditions, the Honeywell was able to raise humidity from 22 percent to 64.5 percent in the same three-hour period, so it’s definitely a capable machine. It’s rated to “medium-size rooms,” which Honeywell defines as 500 to 800 square feet, which might be a bit optimistic—Sawyers felt a decrease in relative humidity compared with previous ultrasonic models he’s used in his rather large bedroom (about 400 square feet), but added that he thought the easy cleaning was an attractive trade-off.

As far as water output goes, we measured it at about 1.9 gallons per day on high, which is a bit lower than the 2.3 gallons Honeywell claims (as was the case with most of the other models we tested), but is in line with most midsize humidifiers. That means you’ll have to fill it twice a day to keep it running 24-hours on drier days.

The HCM-350 is not virtually silent, like the ultrasonic models we tested, but it is still very quiet. We measured its sound level at 48.9 dB(A) from a distance of 1 meter using our sound meter app; this is loud enough that you’ll notice it, but not objectionable since it’s well under the 55 dB(A) it takes to begin interfering with a typical conversation. The level drops down to a barely noticeable 40.3 dB(A) if you set the fan speed to medium.

More important than sound pressure levels, though, the tone and pitch of the noise isn’t piercing or annoying in any way. Rather, it’s a pleasant white noise that sounds like a box fan on a medium to low setting. Suthivarakom, who is used to a warm-mist humidifier, said, “It’s really, really quiet.” Sawyers said, “It got a pretty good hum going on high, but it sounded like the white noise machines we bought for the boys’ rooms, so it’s not unpleasant.”

Including purchase price, cost of consumables, and electricity, it’ll set you back about $300 over the course of its three-year expected service life (assuming you’re running it 24 hours a day, but only in the winter time). That puts it right in the middle of the pack; total costs for the models we tested range from $85 for the budget-oriented Safety 1st to $575 for the Air-O-Swiss, which suffers from expensive demineralization treatments. However, the Honeywell’s roughly $50 initial purchase price was the second-lowest among all the machines we tested, which makes it an appealing value up front.


*At the time of publishing, the price was $11.

Honeywell Humidifier Wick Filter, Single, HAC-504AW
You’ll need a new filter every six months at minimum, and more often if you don’t wash your filters.

Replacement filters ($12) are a simple drop-in affair that anyone can perform. Depending on the hardness of your water, Honeywell recommends replacing the filters every one to three months, though Amazon reviewer Samantha found they lasted six to seven months with regular washing. No tools are needed for installation. It’s normal for the filters to turn brown as the mineral deposits build up, and you can extend the life of the filter by flipping it top to bottom every time you refill the tank, or rinse out the base. Once the filter becomes stiff and saturated with minerals, the wicking ability is impeded so you will notice a drop-off in humidifying ability (and water consumption). So if you notice that there’s more water left in the tank than expected when you go to refill it, it’s probably time to replace or clean the filter.


Who else likes it?

The HCM-350 is well reviewed at Consumer Reports. It just missed the recommended cut (73 versus 86 highest), and they said humidity output, energy efficiency, and convenience were all great, but they had some issues with it that we don’t really agree with (and will cover in the next section).

Top Ten Reviews was also fairly impressed, giving it a score of 8.1/10. They liked its long, three-year warranty and the fact that it was silent, but did not like that it humidified at a slower rate than ultrasonic competitors. Their review concludes, “Although this unit is slightly larger than humidifiers of similar coverage, it offers safe cool mist and effective relief from the dry air in your home.”

It has also been Amazon’s #1 best selling humidifier for quite some time (as of this writing in December 2014), which was our initial reason for calling it in. In addition to being popular, it carries an exceptionally high 4.1-star average for a humidifier (most fall in the 3 to 3.7-star range). Reviewers switching from ultrasonic models note that the lack of white dust is a major pro and also praise its ease of use. The well-designed reservoir was a major pro for Amazon reviewer Tes, who writes in her 5-star review she titled “Best humidifier in 30 years”: “The handle design is the most comfortable and well balanced of any humidifier I’ve ever owned so trips to and from the sink aren’t so awkward. The lid is extremely easy to get off/on and my husband never overtightens this one. The fill tank opening is not only easy to get into but very large so a gushing flow from the tub can fill it up very quickly.”

Flaws but not dealbreakers

The evaporative Honeywell is about as effective as any machine at maintaining a comfortable level of relative humidity, but it takes a bit longer to to get to that comfortable level than its ultrasonic competitors. This means it’s good to give it a bit of a head start before bedtime if you’re not planning on running it 24 hours a day. Sawyers initially reported that turning it on right before bed was not delivering as much humidity as he was used to with the ultrasonic Sunpentown 4010, but after giving it a couple hours’ head start, the air felt much better, though not quite as good as it did when using the Sunpentown. That being said, Sawyers has a rather large bedroom (about 400 square feet) and also said that the easy cleaning was an attractive enough trade-off to keep him from switching back to the ultrasonic model.

The biggest flaw is probably the 1-gallon reservoir, which needs refilling at least once a day compared with the larger ones found in the Air-O-Swiss 7135 (1.7 gallons) and Venta LW25 (2.0 gallons). At the same time, a larger reservoir carries its own drawbacks. They can be more difficult to clean, harder to fit under smaller sinks, and heavier when filled. So you win some and lose some.

The most common complaint from Amazon reviews is from mold growing on the filter, but this is a problem with evaporative wicks in general and is not unique to the HCM-350. This can be avoided in a few ways. First off, you could let it run on empty so that the filter dries out. Or you could try alternating filters. Pull one out and let it dry completely, then swap again the next day.

There’s also no humidistat for this model, but as we previously covered, this isn’t as big of a concern for evaporative models because they are physically incapable of over-humidifying. If you’re really concerned, just run it on medium or low and you’ll be fine. Besides, out of the models we tested that did have humidistats, only half of them were accurate, so it’s not a terribly reliable feature anyway.

Finally, there’s the matter of the germ-killing UV bulb, which you’ll note has hardly been mentioned by us, despite it being prominently featured in the marketing materials. Honeywell refers to an “independent report” that tested UV light as being 99.9 percent effective in killing E. coli and other germs after two hours of exposure. Given the slow rate at which water flows through this machine, it’s certainly possible that the bulb is effective at reducing the amount of funk that reaches the filter. Yet at the same time, it’s not clear that the UV lamp is really effective or well positioned. It only illuminates a small portion of the water as it flows from the tank over to the filter wick.

We don’t think the UV germ-killing abilities are really a selling point for this humidifier.

Product literature states that “Untreated tap water flows from the water tank into the UV water path where it is exposed to ultraviolet light which kills mold, bacteria, fungus, and virus.” However, these should already be at low levels in treated municipal tap water anyway. Besides, if I were designing a UV lamp to keep the critters at bay, I’d like to have it shining all over anything that is going to stay wet, especially the filter, which this does not. Overall, we don’t think the UV germ-killing abilities are really a selling point for this humidifier.

That being said, some users are extremely upset by the fact that replacement bulbs are expensive and must be obtained by either phone or snail mail directly from the manufacturer. We are sympathetic to their indignation in principle because if a company is selling a product that needs replacement parts that are designed to wear out, said parts should be widely available online and/or in store. However, considering that the feature is of dubious efficacy in the first place, and the HCM-350 is still cheaper than many units that don’t have this feature at all, we think it’s better to just pretend that it doesn’t have this feature at all. An indicator light changes from green to red when it’s time to replace the UV lamp. But frankly, we wouldn’t bother replacing it after the first one burns out after about 3,000 hours, or about four months of daily, around-the-clock use. (But if you must replace it, see this footnote for instructions on how to do so.4

As previously mentioned, in their review Consumer Reports lists a number of cons to this unit, but we don’t think their quibbles hold up to close scrutiny.

For example, Consumer Reports dinged the HCM-350 for hard-water performance, which is the percentage of hard tap water put into the machine that is turned into humidity, but this is actually a good thing. Those minerals are what cause the white dust issue and are a potential health hazard as well—you don’t want them in the air.

They also dinged the HCM-350 for the lack of indicator when the tank is empty, but the tank is clear and it’s pretty straightforward to fill it every night before bed (and again in the morning if you want to run it all day).

They also note that there’s no auto shut-off when the tank is empty, but that is not a major issue with evaporative models because unlike ultrasonic models, running an evaporative humidifier on empty won’t break the machine. Indeed, if you intend to let it sit dry for any extended period of time, it’s good to let it run when empty for a while to dry the wick so it doesn’t mold. True, it would be best to lower the fan speed to save energy while drying off the the filter, then shut off when that’s done. But since it uses only 44 watts on high, it’s not a big deal.

Finally, it’s worth noting that with pretty much every non-warm-mist humidifier, running it can make you feel a bit cooler even if it’s not. The actual temperature does not drop according to a thermometer, but Suthivarakom found herself reaching for an extra blanket at night and you might, too.

The runner-up

Also Great

*At the time of publishing, the price was $72.

Sunpentown SU-9210 Digital Evaporative Humidifier
This costs a bit more than our pick and doesn’t have a one-piece reservoir, but it offers comparable performance should our pick go out of stock.

If the Honeywell goes out of stock, the SPT SU-9210 ($70) is another evaporative humidifier we liked in testing. As an evaporative humidifier, the SU-9210 has all the same inherent benefits over ultrasonic models as the Honeywell: lack of white dust and general inability to over-humidify. But it’s not nearly as easy to clean as our top pick (though nothing really is), which ultimately makes it more difficult to live with.

Still, it has a number of useful features that some people might appreciate, including an accurate humidistat for peace of mind and a timer mode, which lets it run from 1 to 10 hours. Consumer Reports also likes it, giving it a recommendation and a score of 79 verus the Honeywell’s 76.

As far as quantitative testing goes, the SPT SU-9210 kept right up with the Honeywell. Its 47.8 dB(A) sound level was right in line with the Honeywell’s 48.9 dB(A) reading, and it increased relative humidity by 19.75 percent in our initial testing setup (compared with the Honeywell’s 14 percent—though the Honeywell started at a higher humidity). When we tested the humidistat’s ability to accurately maintain a RH of 65 percent, it held steady from 62 to 64 percent, which beat out models costing more than twice as much. Speaking of which, its total operating cost of about $200 makes it slightly cheaper than the Honeywell over the course of three years (wicks are two for $20), but ultimately, the Honeywell provides a better overall user experience.

While the Honeywell is specifically designed to be easy to clean, the Sunpentown has many of the typical humidifier design flaws. The hand-wash-only reservoir is made of several plastic pieces fused together, and I’d worry about these leaking over time. On the plus side, the base and reservoir separate from the fan casing (where the electrical bits are) for easy cleaning. But what bothered me most about this model are beeps upon every button push, which is completely unnecessary and irritating.

It is a little over half the size of the Honeywell measuring in at 9 by 14 by 11 inches and weighing a comparatively light 5.6 pounds, but we’d rather have a larger humidifier that’s easier to clean and less annoying. Overall, the SU-9210 is a good unit, but the Honeywell is better.

For larger rooms: a silent Ultrasonic Pick

Also Great
SPT SU-4010 Ultrasonic Dual-Mist Warm/Cool Humidifier with Ion Exchange Filter
Ultrasonic humidifiers are silent and humidify at a faster rate than our pick, but can over-humidify if you’re not careful. This one performs similarly to models costing twice as much. It's good for a space 400 square feet or larger.

The Sunpentown SPT SU-4010 ($75) was our previous runner-up pick and is still a solid and economical performer containing a demineralization cartridge. If you have a larger room (bigger than, say, 400 square feet) and value moisture over ease of maintenance, then this is your best bet. Sawyers found it more effective than the Honeywell in a large bedroom. But he offers this warning: “You can potentially have over-humidification with the Sunpentown—it’s like a powerful vehicle that you can drive recklessly if you lay on the throttle.”

Consumer Reports gave it a Best Buy rating at 86/100. It’s super quiet, even for an ultrasonic humidifier, and has an ion exchange water filter (a filter that draws the calcium and magnesium ions in your water in and then replaces them with sodium ions) to help keep microbial growth and mineral dust to a minimum. The dual mist spouts can be aimed toward the part of the room you want the humidity to hit (or they can be aimed away from things that should stay dry, like, say, a lampshade). Additionally, its tall, thin design (13 by 12 by 5 inches, 7.5 pounds) makes it a good choice for anyone short on table space. It’s also, for what it’s worth, quite pleasant to look at.

The main flaws on this unit are those daily tasks that hold back several humidifiers—cleaning and refilling. The base of the unit has the electronics attached, and mildew tends to build up along several sharp angles inside. This is the one Sawyers had to clean with the vinegar-soaked toothbrush, because total immersion of the base is impossible. The misting spouts tend to dribble water when they’re removed from the tank from refilling. And it’s usually impossible to get the tank from the bathroom back to the bedroom without losing a few drops of water to the floor along the way. That happens even if you overtighten the tank lid, which is too easy to do.

“The flaws in this one seemed fine to me at the time, because it was a step up from our older humidifier, the inexplicable Crane teardrop,” Sawyers said. “But now that I’ve used the Honeywell [our pick], it’s clear there’s a better option out there—for less money.”

The upgrade pick

Step Up
Venta LW25 Airwasher
This needs to be refilled only every 10 days compared with the daily refills required by our other picks. Whether that’s worth an extra $240 is up to you.

The Venta Airwasher LW25 ($260 to $300, depending on where you buy it) is worthy of its high price tag only if you are willing to pay a lot more money up front for lower power consumption and less-frequent cleanings, which can definitely be worth it for a lot of people. While your typical humidifier should be cleaned about every third day, Venta recommends cleaning only every 10 to 14 days and relies on a $19 proprietary chemical mixture to keep funk down between cleanings. A two-week supply (3.5 ounces) is included with the LW25, and the $19 bottle holds 35 ounces, so it’s good for more than 4 months of use.

An inside view of the Venta’s rotating disk and reservoir system.

An inside view of the Venta’s rotating disk and reservoir system.

The Venta works by drawing air over a set of slowly rotating discs. It’s incredibly energy efficient, drawing 7 watts on high, yet effective at humidifying, despite using only 0.2 gallon of water per day. That is not a typo. The LW25 literally uses an order of magnitude less water than the other midsize units we tested to achieve the same amount of humidification (18 percent increase over the three-hour test period)5. In very cold and dry climates, the daily output rate of water can be higher, up to about 1.5 gallons, according to a Venta PR representative.

We speculate that this might be due to the water additives you use with it: quaternary ammonium chlorides and a “water softening agent,” which increase the wet surface area for improved evaporation, disinfect, and reduce mineral buildup. However, despite this extreme efficiency, Venta still requires that you top it off every day in order to maintain maximum humidifying efficiency—it works best when full. (For what it’s worth, I tested it with the reservoir only two-thirds full and found that it was still effective, so it’s not the end of the world if you skip a day or two.)

It’s compact at 12 by 12 by 13 inches and 8.5 pounds, and definitely a better choice than the other air washer we looked at made by Winix, which cost $80 more ($320 versus $240), had a more complicated user interface, and used 0.58 gallon per day, which is nearly three times as much as the Venta. The Winix also used an inferior disk design that required the disks to be inserted in only one way. The cover was similarly uni-directional. The Venta’s symmetric design avoids these drawbacks.

The Venta needs to be rinsed and wiped down only every 10 to 14 days as opposed to every third day—this is its main selling point.

As for cleaning, the Venta needs to be rinsed and wiped down only every 10 to 14 days as opposed to every third day—this is its main selling point. To clean the Venta, drain and rinse the lower housing and disk stack with warm water, wipe the housing and fan blade with a cloth, then fill and add another 3.-ounceo dose of their water treatment additive. Every six months, do a deep clean by filling the reservoir, adding their cleaner, and running on low for two hours, followed by rinsing with warm water per usual.

The Venta draws an improbably low 0.03 amps when running on high. That’s less than an LED lightbulb.

The Venta draws an improbably low 0.03 amp when running on high. That’s less than an LED bulb.

Despite its high sticker price and moderately high cost of the chemicals (about $40 per year), the overall price tag of the Venta spread out over a three-year operating life is relatively low. At $425, it’s the second most expensive, but an impossibly low electricity cost of just $15 makes it a lot more affordable than one would expect. However, unlike the Honeywell, the Venta comes only with a two-year warranty, which is better than your typical one-year affair, but we’d like to see more from a nearly $300 unit.

As a final note on this machine, we were not impressed with its so-called “air washing” abilities. To test whether this machine was comparable to an actual air purifier, we used a laboratory-quality bench top optical particle counter that measured particles in the 0.5- to 20-micron range to measure airborne particle concentrations before and after three hours of testing. Background particle concentrations ranged from 65 to 200 particles per cubic centimeter. At the end of the testing period, the Venta lowered the particle concentration from a starting concentration of 180 particles per cubic centimeter, to a final concentration of 9, which  sounds impressive, until you consider that the Honeywell, which makes no claims of air purification, got it down to 14 in a similar test (though the Winix air washer strangely did nothing to reduce particle counts). For reference, a HEPA-certified air purifier would bring this number down to virtually zero in less than half an hour.

You should get this unit because you want a humidifier that doesn’t need to be cleaned basically every other day, not because of its air-purification abilities.

Furthermore, this reduction in larger particles says nothing about the smaller particles, like smoke, that air purifiers are so effective at eliminating. Indeed, Consumer Reports conducted their own testing back in 2008 on the older LW_4 series air washers and concluded that “Both models we tested proved no better at removing dust and smoke than no air purifier at all.” Overall, you should get this unit because you want a humidifier that doesn’t need to be cleaned basically every other day, not because of its air-purification abilities.

Care and maintenance

Regardless of which type of humidifier you have, you’re going to need to clean it regularly to prevent funky stuff from growing in the reservoir and other parts of your humidifier. The US EPA suggests cleaning and disinfecting portable humidifiers every third day. Typically, water and elbow grease will get the job done, but you may need to use distilled white vinegar every so often to remove mineral deposits (scale).

Soap and other chemicals should generally be avoided because if you don’t thoroughly rinse it off, it’s going to get vaporized and you’ll end up breathing it. After the descaling step, rinse all surfaces with either 1 teaspoon of bleach mixed with a gallon of water or a 3 percent hydrogen peroxide solution to disinfect and then wipe dry.

As previously touched upon, you will need to perform occasional wick maintenance on your evaporative humidifier. To clean an evaporative wick, soak it in cold water for 20 minutes and gently swish it back and forth to release minerals. Never use hot water or chemicals. To avoid mold growth on the filter, when you turn the humidifier off, pull out the filter and let it dry, or leave it in and let the fan run with no water until dry. But you can’t clean the same wick forever without the antimicrobial treatment wearing off, so you’re going to have to replace it every six months at a minimum (though this could be as often as every month if you have very hard water).

Ultrasonic humidifiers do not have wicks, but most do have some kind of demineralization cartridge or treatment that will need to be replaced every so often. Our Sunpentown ultrasonic pick has a $25 cartridge that they recommend swapping out every six months.

As for the air washers, Venta recommends refilling water daily in order to keep the reservoir nearly full, where the rotating disks will be fully submerged, meaning it will be more effective at humidifying. Every 10 to 14 days, drain and rinse the lower housing and disk stack with warm water, wipe housing and fan blade with a cloth, then fill and add another dose of 3.5 ounces of their water treatment additive. Every six months, do a deep clean by filling the reservoir, adding their cleaner, and running on low for two hours, followed by rinsing with warm water per usual. To give the housing a thorough cleaning, disassemble the upper housing (no tools required) and wipe surfaces with a damp cloth.

How we tested

Testing was performed this fall in my 160-square-foot office with standard 8-foot ceilings. I live in Southern California, in a 1960s house, typical of that era in that it is pretty leaky, compared with the tighter construction of new homes built with the newfangled concept of energy efficiency. We came up with the following questions.

Are any humidifiers too loud to live with?

Sound pressure levels of each unit running on high and measured at a distance of 1 meter away and 0.5 meter above the ground. Measurements were taken with an iPhone 5S running a NoiSee app, one of the top recommended apps in a survey of 192 apps by the National Institute for Occupational Safety and Health (NIOSH), where it came within +/-2 dB(A) of reference measurements. That’s plenty accurate for our purposes.

A noise level of 55 dB(A), about the highest that would not interfere with normal conversation (60 dB(A)) was used as a selection criteria. For reference, a quiet office is 40 dB(A), moderate rainfall is 50 dB(A), and normal conversation is around 60 dB(A).

Only one humidifier failed this test. The Stadler Form Hera came in at a painfully loud 74 dB(A). We suspect it was a defective unit, as there is no reason for an ultrasonic humidifier to make this kind of racket. It was too loud to even continue with the remaining test, so it was out. Of the remaining humidifiers, we did not test the ultrasonic models with the sound pressure meter. They were all nearly silent, less than 40 dB(A), blending in well with the background noise (34 dB(A)).

How high can these humidifiers raise the humidity of a 160-square-foot room in three hours when running on high?

This is a question we addressed in our previous guide, and going into the update, we thought it was going to be one of the most important tests. If the humidifier can’t raise the humidity in a dry room, none of the other tests matter. The humidity depends strongly on the air temperature, and we wanted to hold this at a constant 20 +- 1 degrees Celsius (68 +- 1.8 degrees Fahrenheit). Since heated winter air can be as low as 5 to 10 percent RH, and desired ranges are 30 to 50 percent, we wanted to start with the humidity as low as possible. We tried everything we could to get to these conditions using three dehumidifiers, a 12,000-BTU portable A/C unit, and a portable 1,500-watt electric heater. (No, I don’t want to see my power bill.) Even with all these, we were unable to get to a stable starting condition of 20 degrees Celsius, 30 percent RH condition. So we settled for what we could get, which was running the tests near 22 degrees Celsius and about 50 percent RH for starters.

Using testing conditions of 22 C +-0.7 degrees, and average starting humidity 48.1 +-7.1 percent, humidifiers were filled with 2 liters of tap water and run for three hours on their highest setting. Temperature and humidity levels were measured every 15 seconds using two Lascar high-accuracy USB data loggers. They have a temperature accuracy of +-1 degree, and humidity accuracy of +-2%. One logger was placed 1 meter from the humidifier located on a 1-meter stool near one wall, and the other was placed on a desk on the far side of the room. There was good agreement between the sensors, except for some of the ultrasonic humidifiers when the humidity near the unit would be 5 to 10 percent higher. For our purposes, the values were averaged.

Figure 1. Increase in relative humidity over a three-hour period with humidifiers running on their highest setting.

The increase in humidity after three hours ranged from 14 to 34 percent, but was typically in the 15 to 20 percent range. The Air-O-Swiss 7135 had the biggest increase of 34 percent, but it made a sopping wet mess on the floor in the process. In a series of tests, Honeywell brought the humidity up 14 percent, from 50 to 64 percent. Another test in a slightly smaller room (120 square feet) saw it raise the humidity from 22 to 64.5 percent in three hours, so it’s definitely a capable machine.

We learned a lot from the test. First, all the units were effective at increasing the humidity, generally from a comfortable 50 percent to a moist 65 percent. This is higher than recommended, yet still pleasant. Second, we repeated the tests and found there was quite a bit of variability, even with basically the same starting conditions. Finally, the two evaporative units, the Honeywell  and SU-9210, and two air washers top out the humidity at 60 to 65 percent, so there is little hazard of adding too much water to your room. All units were effective at raising the humidity, but the ultrasonic models have an ability to over-humidify and make a mess on the floor.

How well can the units with humidistats hold the humidity using a 65 percent RH set point?

The humidifiers with humidistats were evaluated to see how well they could hold the humidity steady at 65 percent. That’s higher than you’d need, but we wanted to push the envelope to see what they could do.

The SPT SU-9210 was the only unit capable of holding the humidity nearly constant, beginning at 62 percent and ending at 64 percent. The AOS 7135 did poorly, ramping the humidity from 50 percent way past 65 percent ending at 75 percent. The SPT SU3600 also failed, as the humidistat read a steady 33 percent and it sent the humidity soaring from 60 to 77 percent.

All the non-ultrasonic models were able to reach and hold humidities in the 60 to 65 percent range, even without a humidistat.

From this test, and a bit of research, we learned that humidity is a tricky measurement to make. The budget humidistats built into some humidifiers are not consistently up to the task. Even among humidistats from the same manufacturer, one worked (SU-9210) and one didn’t (SU-3600). The previous year’s Air-O-Swiss 7135 model had a humidistat that worked well and held the humidity within a couple of percent. In our current model of the AOS 7135, the humidistat was off by at least 12.5 percent.

What is the rate of water usage when all run at the same time (outside) compared to the manufacturer’s specification?

The units produced output rates between 1.1 and 2.4 gallons per day, about three-quarters of the manufacturer’s specification. We would expect the rate of output to be higher under extremely dry conditions. The Airwashers Venta and Winix were an exception in this test, outputting only 0.2 and 0.6 gallon per day, respectively. With an output rate that low for the Venta, we’d be worried about it having enough oomph, yet it performed well indoors, raising humidity levels 21.8 percent over three hours.

Figure 2,  Comparison of the humidifiers daily output rate compared with manufacturers specification. From left to right, evaporative models (Honeywell and SU-9210), Ultrasonic models (SU-4010, Safety 1st, AOS7135), and Airwasher models (Venta, Winix). The ultrasonic models as a group came closest to spec, followed by the evaporative models, which are more sensitive to ambient conditions. At very dry conditions their rate of output will increase.

Are the “air washers” effective at removing particles?

For the air washers, which claim to remove particles from the air, airborne particle concentrations were measured at the beginning of the test, and after three hours of running. We used a laboratory quality bench top optical particle counter that measured particles in the 0.5- to 20-micron range. Background particle concentrations ranged from 65 to 200 particles per cubic centimeter.

After running the Venta and Winix air washers and our top pick, the Honeywell HCM-350 evaporative humidifier, we saw the particle concentrations drop for the Venta and Honeywell, but rise for the Winix.

The Venta lowered the particle concentration from a starting concentration of 180 to a final 9 (#/cm^3). Not nearly as clean as a stand-alone as the dedicated air purifiers tested for our best air purifier guide, but still an order of magnitude reduction. However, the Honeywell, which isn’t marketed as an air washer, but still has air flowing through a wet filter, also saw the particle concentration change from 65 down to 14 particles per cubic centimeter, so we’re not prepared to tout this machine the Venta for its so-called air-washing abilities.

The Winix, however, didn’t reduce particle counts at all. They started at 70 and climbed to 150 (#/cm^3) after three hours.

Looking into these claims of air washing, I found that in 2008, Consumer Reports evaluated the Venta’s effectiveness in removing much smaller particles (0.1 to 3 microns) and found they were ineffective.

Our take is that air washers and humidifiers can remove some larger particles (0.5 to 20 micron) like pollen and dust mites, but not nearly well as a dedicated air purifier.

How much does it cost to operate over the lifetime of the machine (three years) ?

The cost of ownership was calculated over an expected product lifetime of three years, running 24 hours a day, for six months a year.

Power consumption of humidifiers was measured on the high setting using a Sperry DSA-500 clamp-on ammeter. The table below and calculations used for cost of ownership are based on the highest setting. Electricity rates are based on residential rates in my area of 0.15396 ($/kWh) and operation 24 hours a day. Consumables can include wick filters, demineralization cartridges, and antimicrobial silver cartridges.

Model Purchase Consumables Electricity Total Cost
AOS 7135 $180 $294 $100 $574
Honeywell $52 $154 $90 $296
Safety 1st $26 $0 $56 $82
SU-4010 $75 $90 $53 $218
SU-9210 $80 $54 $75 $209
Venta $300 $110 $15 $425
Winix $320 $0 $22 $342

Table 1. Cost of ownership over expected three-year lifetime of humidifiers. Costs were calculated for seasonal usage, six months out of the year, over three years, for a total of 18 months.

The competition

If you must have a step down, the $30 Safety 1st works, which is impressive for such a cheap unit, but its drawbacks keep it from being an official pick. It’s not a bad deal for about $30, but you’re going to get only that much worth of humidifier. It’s like buying a $3 bottle of wine. It can be good for $3, but that doesn’t mean it’s objectively good. As far as performance goes, the Safety 1st is an ultrasonic humidifier, so it runs very quietly and is capable of outputting a fair amount of moisture—it raised our test area’s relative humidity by 17.5 percent over our three-hour testing period. But it’s limited by a tiny 0.8-gallon reservoir that will need frequent refilling, and it lacks a mineral filter, which means you’ll have to use distilled water if you want to avoid mineral dust issues (which you do). Also, it has a two-piece reservoir with a small opening (making it hard to clean) and a long list of user reviews that complain about leaking and other problems—more than 25 percent of the 840 total reviews as of this writing are one- or two-star reviews.

The Air-O-Swiss 7135 was our previous top pick because of its silent operation, humidistat, and prodigious moisture output. Indeed, that it was able to raise an already-moist room’s relative humidity by 34 percent is quite impressive (though it did create a big puddle around the base in the process of doing so). Previously, we had put a lot of value into this humidifying ability, but based on feedback we’ve gotten, it’s more than most people need and more than most people want to pay. Its $180 street price is already high. Add the highest cost of consumables (water treatments/demineralization cartridges) and electricity ($100 over three years) and you get the humidifier with the highest cost of ownership by far—even compared with the $300 Venta and $320 Winix. What’s more, the humidistat completely failed to maintain a consistent level of humidity in this round of testing.

The Winix Air Washer ($320) was effective at humidifying, but had no effect at removing particles and did little to justify its exorbitant price tag. While it uses the same basic technology as the Venta, the design made it more difficult to use. The base reservoir was not symmetric, and the set-up disks had to be inserted in the correct orientation. On the plus side, it doesn’t use any expensive, proprietary cleaning chemicals or water treatments. This leads to a lower overall cost of ownership. But you’d still have to clean the machine somehow using chemicals that won’t negatively affect your air quality. We think Venta’s approach is more user-friendly in this way because you know exactly what you need to get and how to use it. Sure, it costs more, but it’s money worth spending.

The SPT-SU3600 ($80) is Sunpentown’s newest humidifier, which crams a fairly capable machine into a compact, stylish package that would fit on most night stands. However, it’s a one step forward, two steps back situation. We liked the small size, and it’s nice that the one-gallon reservoir has a fill cap that seals in an eighth of a turn. But that’s offset by annoying touch-sensitive controls that offer no tactile feedback. You can’t tell what you are doing without  looking. It also has a wildly inaccurate humidistat, which read 33 percent for the duration of a run designed to test its ability to hold the humidity constant at 65 percent. Instead of holding steady here, it pumped up the humidity to a muggy 77 percent and soaked the floor. And it’s missing a demineralization cartridge, so you’ll have white dust to contend with or the added cost of distilled water. If you prefer an ultrasonic model, you’d be better off skipping this one and going with the SU-4010, which has easier to use controls and a mineral filter.

The Stadler Form Hera ($200) is billed as a top-shelf unit, with an attractive feature set containing warm and cool mist ultrasonic mists with bi-directional nozzles, humidistat, and a night mode that automatically dims the display. Given the $200 price tag, it really must deliver performance in order to justify the high cost. However, our unit generated excessive screeching noise measured at 74 dB! The humidifier put out mist, but was so loud that we aborted our tests. It’s well reviewed at Allergy Buyer’s Club, and I can’t imagine anyone tolerating this noise level, so perhaps our tester was defective. Amazon reviewer Matt states, “Maybe this humidifier provides more advanced features than other models, but since it doesn’t get the basics right it really doesn’t matter.” We have to agree.

The competition: what else we looked at

  •       Air-O-Swiss 7142 (860 square feet, $200) Ultrasonic model, low 2.9 stars on Amazon. It’s highly rated when new at Top Ten Review and Allergy Buyers Club, but exceeds our 650-square-foot rating (860-square-foot),and it still has the same 3.5-gallon output as AOS 7135. Amazon reviewers report that failure over time, dying just after a year, poor customer service, inaccurate humidistat.
  •       Air-O-Swiss 7144 (650 square feet, $200) Ultrasonic model, not very different from other AOS models, and smaller reservoir.
  •       Air-O-Swiss 7145 (540 square feet, $140) Ultrasonic model, out of stock … discontinued and replaced by 7147.
  •       Air-O-Swiss 7147 (650 square feet, $169) Ultrasonic model, smaller reservoir than 7135, not as efficient in previous Wirecutter tests.
  •       Bionaire 1 Gal. Warm and Cool Mist Ultrasonic Humidifier (N/A square feet, $120) Ultrasonic model, not enough information to evaluate. Available at Best Buy, but sold out on Amazon. Not listed on Bionaire website as current product.
  •       Bionaire Ultrasonic Filter-Free Tower Humidifier (Medium-size room, $80) Ultrasonic model, not much info to evaluate.
  •       Crane Cool Mist Humidifier (250 square feet, $45) Ultrasonic model, During previous Wirecutter testing, the output was extremely low (0.5 gallons per day).
  •       Crane Cube 0.5 Gal. Ultrasonic Cool Mist Humidifier (250 square feet, $40) Ultrasonic model, tiny 0.5 gallon reservoir.
  •       Crane Germ Defense EE-8064 (500 square feet, $105) Ultrasonic model, Consumer Reports noted similar to EE-8065, but $40 more expensive.
  •       Crane Germ Defense EE-8065 (500 square feet, $65) Ultrasonic model, decent unit recommended by Consumer Reports, but the indicator lights are super bright.
  •       Crane Owl (250 square feet, $40) Ultrasonic model, too small, and while rated to 250 sq ft, its output is only 1.4 gallons. Cute animals are not a good fit for everyone.
  •       Essick MA1201 (2500 square feet, $110) Evaporative model, whole house unit that’s too big for most people, but excellent value.
  •       Holmes Smart Humidifier with WeMo (2,500 square feet, $200) Evaporative model, whole house unit, much bigger model than we’re considering.
  •       HoMedics UHE-CM25 (100 square feet, $50) Ultrasonic model, too small, only rated to 100 sq ft.
  •       HoMedics UHE-CM45 (100 square feet, $60) Ultrasonic model, too small, only rated to 100 sq ft.
  •       Honeywell HCM-300T (1,050 square feet , $80) Evaporative model, rated for bigger area >650 sq ft.
  •       Honeywell HCM-6009 (1,900 square feet, $69) Evaporative model, whole house console unit, much bigger than other models in this survey.
  •       Honeywell HCM-6011G Humidifier Quietcare Cool Mist Humidifier (2,300 square feet, $130) Evaporative model, whole house unit. Too big.
  •       Honeywell HCM-631 (1,050 square feet, $40) Evaporative model, rated for areas > 1050 sq ft, out of stock.
  •       Honeywell HUT-300 (400 square feet, $70) Ultrasonic model, User reviews from Amazon indicate it is hard to clean, and the reservoir is small (0.8 gallon) reservoir.
  •       Honeywell HWM-340W  (600 square feet, $50) Vaporizer model, warm mist only, 400 Watts to operate!
  •       Honeywell Mistmate (150 square feet, $30) Ultrasonic model, too small, only rated to 150 sq ft.
  •       Honeywell HWM 450 (1400 square feet, $50) Heated model, ruled out from negative Amazon reviews of unit burning itself out.
  •       Pure Guardian 0.2 Gal. Ultrasonic Cool Mist Humidifier (125 square feet, $40) Ultrasonic model, too small, only rated to 125 sq ft.
  •       Pure Guardian Elite 1.3 Gal. Ultrasonic Humidifier (300 square feet, $150) Ultrasonic model, pricey for room size.
  •       Stadler Form William (1,000 square feet, $240) Evaporative model, high cost and rated at >1000 sq ft.
  •       Vicks V3100 (small – medium, $30) Evaporative model, 1.2 gallons per day too low an output.
  •       Vicks V5100NS (400 square feet, $50) Ultrasonic model, top-rated Consumer Reports medium room size, but consistently poor Amazon reviews with multiple concerns of a noxious chemical smell and higher-than-normal dead on arrivals, 3 stars of 60 reviews, no longer available at Best Buy.
  •       Vicks Warm Mist V750 (1,000 square feet, $30) Heated  model, only warm mist, so energy usage is too high.

Wrapping it up

If you are troubled by symptoms (dry itchy skin, dry irritated sinuses, and cracked lips) caused by dry winter air or live in an especially dry climate, our picks are effective and easy to operate. Just stay on top of the daily filling and cleaning every three days to keep the mold and bacteria at bay. The Honeywell HCM-350 is a simple and durable humidifier that’s super easy to clean. If you’d prefer a nearly silent ultrasonic model, the SPT SU-4010 is a good pick. Finally, if you want a low maintenance and large reservoir model, the Venta LW25 is what you need.


1. The US Consumer Product Safety Commission (CPSC) put out a safety alert in 2012 that dirty humidifiers may cause health problems. They found that bacteria and fungi often grow in tanks of humidifiers. These can grow on scale (a crusty deposit), so it’s important to stay on top of cleaning.

The US Environmental Protection Agency Indoor Air Facts No. 8 document describes the use and care of home humidifiers. They note that recent studies have shown that ultrasonic and impeller humidifiers can disperse minerals and microorganisms that cause inflammation of lungs. But they go on to say it’s not a big deal, except for young, elderly, and people with lung diseases, with a carefully worded statement: “The Federal government has not concluded that the dispersal of minerals by home humidifiers poses a serious health risk.” And they have suggestions for use and cleaning to minimize dispersion of pollutants. They recommend cleaning every three days with 3 percent hydrogen peroxide, then wiping dry.

In an interview with CW2/FOX 31, the medical director of Children’s Breathing Institute and professor of pediatrics Robin Deterding, MD, cautions that ultrasonic humidifiers can create white dust and disperse organisms into the air. Both of these can be harmful to the lungs, especially in babies and young children.

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2. Ultrasonic models are not recommended for floor use, and manufacturers recommend they are located 1 meter or more off the ground, as the mist can settle and wet the floor if they are resting on the floor.

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3. Typical new home master bedrooms are 309 square feet. Other bedrooms add up to 481 square feet combined, according to National Association of Home Builders. Given that there are a lot more existing homes and apartments, we estimate 100–200 as typical.

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  1. Part Number: HCM-350-UV     Item Description:    $16
  2. Telephone: 800-477-0457 (M-F 7:30AM-7:00PM EST) with Visa, Mastercard or Discover (All of US and Canada).  Please first push option 1 “for assistance” and then option 2 “for all other questions.  Our winter “order department” cannot take this order, so please do not push the option “to place an order”From the first menu please press 4 and then press option 7.  This will direct you to a Consumer Relations Representative who will be able to take the order. If you choose the “to place an order” option from the main menu they will tell you they cannot take this order.
  3. Mail: Send check or money order to:Kaz, Inc
    Consumer Relations
    250 Turnpike Road
    Southborough, MA 01772Shipping and handling for all telephone and mail orders is a flat $4.95 per order for parts, filters, and accessories. Please add applicable sales tax for TX, NY, CA, FL, MS, and MA.  Orders being shipped to Canada are subject to duty and/or brokerage charges at the time of delivery.”

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5. At first, we weren’t sure what to make of this, so I ran the numbers. I did some calculations, and to raise the humidity 20% in the test area at 22˚C, you’d technically need only 0.04 gallons (0.15 Liters). Typically, you’ll need a lot more because no room in a typical residential house is perfectly sealed. We reached out to Venta to see why the LW25 performs so differently from other humidifiers in this regard, but never heard back (probably a secret sauce thing). But what’s most important is that it works—however befuddling that may be.

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*At the time of publishing, the price was $70.

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  1. "You’ll want to keep the relative humidity levels in your home somewhere between 30% to 50%."
  2. Humidifier buying guide, Consumer Reports, September 2012
  3. Dr. Deborah Cullen, Interim Chair, Family Health Dept., Director for Faculty Development & Advancement, Indiana University School of Nursing

Originally published: February 25, 2015

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