After more than 100 hours of research (including 80-plus hours of lab testing) in the past four years, the Honeywell HCM-350 Germ Free Cool Mist Humidifier remains our pick as the best humidifier for most people. It’s quiet, leakproof, effective, and energy-efficient, and it’s the easiest model to fill and clean we’ve ever found.
The Honeywell’s evaporative technology (as opposed to ultrasonic or warm mist), avoids problems common to the other methods, like overhumidification, pools of condensed water around the base, and white mineral dust building up on nearby surfaces. The HCM-350 Germ Free Cool Mist Humidifier is easier to keep clean than nearly every other humidifier we’ve tested, because every part that touches water is free of electronic components and lacks the sharp angles that harbor buildup. And the HCM-350 is the only humidifier we’ve found that has a seamless, molded reservoir, which eliminates a problem common in inferior models: leaks. Evaporative humidifiers like this are not the most powerful type, but in less than two hours, the Honeywell reaches and maintains a comfortable level of humidity in a room up to about 400 square feet.
If the Honeywell is unavailable, the Sunpentown SU-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 touch water. It even adds a humidistat (which is accurate, according to our testing). However, the SU-9210 costs a bit more up front, has annoying beeping buttons, and lacks a one-piece reservoir, which could lead to leaks in the long run. Like the Honeywell, its evaporative humidifying mechanism doesn’t have as much power as an ultrasonic model, and it reaches its limit in a room of about 400 square feet.
For spaces around 400 square feet or larger, consider the Sunpentown SU-4010 Dual Mist Humidifier with ION Exchange Filter. It’s ultrasonic, which means it’s more powerful than our evaporative picks, but this model (like any humidifier of its type) can spread an annoying layer of mineral dust, and can overhumidify a room. This model stands apart with a level of power that matches the leaders in its category and a price that’s roughly half of some competitors. It doesn’t have a humidistat, but in our testing, they usually aren’t that accurate. The SU-4010 is also harder to clean than the evaporative picks because the water tray is full of sharp angles—a shared trait among all the ultrasonic humidifiers we considered.
For an extremely efficient evaporative humidifier that requires less-frequent cleaning and refilling than our other recommendations, get the Venta Airwasher LW25. At its current price of around $300 it is very expensive, although its high upfront cost is somewhat mitigated by its extreme energy efficiency in the long run. It uses 0.2 gallons of water per day—far less water than the other midsize units we tested, and yet it achieves the same amount of humidification, and it’s best for large-bedroom-sized spaces like our other evaporative picks. Its competitors require multiple cleanings per month, but Venta recommends rinsing this unit every two weeks and thoroughly cleaning it every six months.
The Vicks Warm Mist V750 has cheap-feeling plastic and a wobbly assembly, but hey, it’s inexpensive, and it performed above average in our testing, raising the humidity levels from 60 to 82.5 percent over a three-hour period. It is a popular model on Amazon, but be warned that all warm-mist humidifiers have safety and running-cost concerns—and they don’t humidify a room any better than non-warm competitors.
With the help of a PhD physicist, 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 for achieving optimal (and safe) performance. Our humidifier testing in the fall of 2015 featured eight new models, plus a retest of the Honeywell and our runner-up, the Sunpentown SU-9210, and in the fall of 2016, we considered four new models and dismissed them without additional testing.
John has studied atmospheric physics and chemistry in places from the continental US to the Arctic to the remote island nation of the Maldives on government-sponsored field campaigns to improve our understanding of Earth’s climate.
To test home-humidifier models in a climate-controlled space, he weather-sealed his home office and installed an air conditioner to maintain stable initial conditions. He evaluated the humidifiers with two portable temperature and humidity data loggers, and used a laboratory-grade particle counter to size up the air washers (read more in How we tested).
If you are bothered by any of the symptoms caused by dry air, such as dry sinuses, nosebleeds, cracked and sore lips, or shocks from static electricity, the air in your home is likely too dry. 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. (You’ll want to keep the relative humidity levels in your home somewhere between 30 and 50 percent, which will alleviate the symptoms listed above while discouraging mold and mildew, which thrive in damp air. If you want to test your air before buying a humidifier, you can get a hygrometer on Amazon for about $10.)
However, humidifying your home involves more than just buying one of our picks and filling it with water. If you don’t take care to maintain it properly (see Health risks of a dirty humidifier), a humidifier can do more harm than good. Most humidifiers require regular maintenance, including a thorough cleaning every one to three days. There are exceptions, like our upgrade pick. But be honest with yourself: Are you ready to be a “humidifier parent”? If you know you’re not up for this level of regular cleaning and maintenance, you may end up with a breeding ground for germs.
This is the fourth iteration of this guide, so we went into our latest testing with considerable knowledge of what to look for. Once again, we researched popular models on Amazon, reviewed the latest testing from Consumer Reports (subscription required), consulted Allergy Buyers Club, Top Ten Reviews, Best Buy, and ConsumerSearch, and also read the comments from our previous guide for feedback and suggestions from our readers.
Our focus remained on portable models that work either on the floor 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 bedroom (which is primarily where these are used), and plenty for most larger rooms in most homes. Though there are large console units capable of humidifying an entire floor of a home, we didn’t consider them, because at that point, you’re better off installing something directly into your HVAC system.
Humidifier technologies have different pros and cons:
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. Ultrasonics also are prone to producing so much vapor that it condenses on floors, rugs, and furniture, resulting in wet spots and, potentially, damage.
And though fast humidification is a good thing for a dry house, if your house is already comfortably humidified because you’ve run the machine for a while, continuing to humidify will lead to overhumidification 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, many of the humidistat-equipped machines we tested failed to provide accurate readings—we observed discrepancies as large as 43 percent 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.
Evaporative humidifiers use 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. The process is slower than that of ultrasonic models, but it has the big advantage of automatically preventing overhumidification: The evaporative process slows as the air gets wetter. That means they won’t produce condensation on floors and other surfaces.
Evaporative models are also among the cleanest, because any minerals left behind are trapped in the wicking filter, so they don’t produce deposits of white mineral dust like ultrasonics often do. The wick filters do need to be replaced, or at least cleaned, every one to three months. They’re also louder than ultrasonics, but still very quiet—no louder than a small room fan—and the “white noise” they produce is inoffensive, and even soothing.
“Air-washing,” the third technology we considered, is really just a variation on evaporative humidification. The difference is that instead of a stationary wick, these humidifiers 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. They have the advantage of requiring less-frequent cleaning.
Warm-mist and impeller are the other humidification methods we considered. Warm-mist humidifiers work by heating water into steam. As you might guess, this is not terribly energy-efficient. However, some people like the minor warmth that they add to the air. 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 they can produce a white dust. The moisture output is low and the customer ratings on Amazon are so bad that we skipped impeller humidifiers entirely.
With that in mind, we built a list of potential models to test—as of now, it includes 65 different humidifiers.
The Honeywell HCM-350 Germ Free Cool Mist Humidifier is affordable, and it performed consistently well across all categories we tested. Though it didn’t top the charts, it was a solid performer, raising the relative humidity of John’s office by 14 percentage points over the course of three hours. 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 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 HCM-350’s ease of use and cleaning are far better than its competitors, beginning with the fact that 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 people 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, which contain electronics in the base that require you to clean them by hand.
It’s an evaporative humidifier, and you get all the solid benefits and (minor) drawbacks common to that design. It’s energy-efficient and mechanically it’s very simple, meaning there’s very little in the unit that can break. Because it evaporates water, rather than spraying a fine mist like ultrasonic humidifiers, all the minerals in the water get left behind on the wick—you won’t wind up with white mineral dust all over the floor and furniture. (In reviews, owners of ultrasonic models often complain that they get white dust even when they use the included demineralization treatments.)
And because the evaporative process slows down the more humid the air gets, the HCM-350 is self-regulating: It can’t overhumidify a room the way ultrasonics can, and it won’t create puddles of condensation around the machine like they can, either. This also means you can put it on the floor behind a couch or in a corner without having to worry about water on the floor; ultrasonic models typically need to be raised on a shelf or table.
Because evaporative humidifiers use a fan to blow air across the damp wick, they make a small amount of noise—but it’s a neutral, even calming, white noise that few people find objectionable. We measured the HCM-350’s sound level on high at 48.9 decibels from a distance of 1 meter; that’s well under the 55 decibels it takes to begin interfering with a typical conversation. The noise drops down to a barely noticeable 40.3 decibels if you set the fan speed to medium.
Evaporation is slower than ultrasonic humidification, but again, the HCM-350 easily raised the humidity in our test room by double digits within a few hours.
The reservoir is 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 1¾-inch-diameter fill hole, which is only big enough for two fingers, or the Sunpentown SU-4010’s, which can fit a hand but not an arm. For the most part, simply filling this tank with warm water and giving it a good shake should suffice.
The reservoir is also the easiest to fill. Sure, its one-gallon size means you’re going to have to fill it more often (about twice a day if you’re running it on high) but it fits under an average bathroom sink just fine. The tank’s thick, molded handle will support it while filling, so you don’t need to hold the tank in place, a feature appreciated by Sweethome’s executive editor Ganda Suthivarakom. Senior editor Harry Sawyers liked that it barely dripped at all when lifted from its base for the next refill. The handle also provides comfortable transportation that all testers appreciated.
Finally, the reservoir is more durable than other models’ because it’s blow-molded from a single, continuous piece of plastic (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 warranties.
But, of course, none of this would matter if the HCM-350 didn’t also perform well in testing. Though it never topped the charts, it performed consistently well in all measurable categories. In our initial series of tests, it raised the relative humidity of John’s 160-square-foot office by 14 percent (from 50 to 64 percent) over the course of a three-hour testing period.
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 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.
Including purchase price, cost of new filters, 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 wintertime). That puts it right in the middle of the pack.
*At the time of publishing, the price was $10.
Replacement filters are a simple drop-in affair. Depending on the hardness of your water, Honeywell recommends replacing the filters every one to three months. 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.
In January 2016 we investigated several complaints from readers about replacement filters for our humidifier pick, the Honeywell HCM-350. The complaints included poor fit and that the replacements were thinner than the originals, looked different, and/or did not perform satisfactorily. We spoke at length with a representative of Kaz, the manufacturer of the HCM-350. In addition to answering our questions, the representative sent photographs and a physical sample of the current-issue replacement filter. We also independently ordered a replacement filter from Amazon to be sure we were getting the same model that our readers would. Finally, we compared the original filter in our test model to the replacement filters. Here’s what we learned:
Wirecutter senior editor Michael Zhao and Sweethome writer Kevin Purdy have each used a Honeywell HCM-350 for several winters.
Michael, who lives in a radiator-heated New York City apartment and uses the Honeywell in the bedroom, said, “It’s so easy to clean that I actually clean it. Which is pretty great.” Cleaning is also really important—and ease of cleaning is one of our main reasons for recommending the Honeywell. Michael adds that “it’s annoying that the fan collects dust, but I’ve found that the protective screen comes off cleanly if you give it a good tug with needlenose pliers.” That allows him to wipe the fan off (and reinstall the screen) without much fuss. After moving from an apartment with a standard 8-foot ceiling to one with 12-foot ceilings—a big jump in volume if not area, as both rooms are about 150 square feet—Michael noted an apparent drop-off in absolute humidification, but also notes that the unit is still effective at reducing the symptoms of dry air, such as waking with a dry throat. Additionally, he owns a cat, and has found that the wick collects pet hair; a weekly vacuuming (a 2-minute job) clears that up.
Kevin and his wife live in a forced-air-heated Victorian house in Buffalo, New York; it gets very dry in the winter, and they also use their Honeywell in the bedroom. Kevin admits to being “an anti-hypochondriac” and “on the far left end of maintenance,” meaning he doesn’t clean his unit with any sense of urgency. He has generally given the Honeywell’s reservoir a scrub with dish soap once a week, and not cleaned the base plate or the filter with any regularity. He also has let water sit in the reservoir for days at a time. He adds: “I have not had anything bad happen to me.” Fine, but honestly, he should follow manufacturer guidelines for any humidifier, or else risk serious illness; in the case of the Honeywell, that includes a daily rinse of the reservoir and base unit, and occasional cleaning and drying of the wick and sterilization of the other wet parts. In terms of the HCM-350’s performance, Kevin says: “It works really well, and it doesn’t look terribly ugly in our bedroom. It hides in a corner and does the job.”
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 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.
The 1-gallon reservoir is on the small side, and needs refilling at least once a day—although the same is true of our runner-up evaporative model, the Sunpentown SU-9210, and our pick for large rooms, the Sunpentown SU-4010. 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.
The most common complaint from Amazon reviews is mold growing on the filter, but this is a problem with evaporative wicks in general and is not unique to the HCM-350. Following the manufacturer’s cleaning guidelines will help eliminate this problem; alternating between two filters every other day, and letting them dry completely between uses, is another safeguard.
This model also has no humidistat, but as we previously covered, this isn’t a big concern for evaporative models because they are physically incapable of overhumidifying. 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 we’ve hardly mentioned, despite it being prominently featured in this model’s 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. Overall, we don’t think the UV germ-killing abilities are really a selling point for this humidifier.
That being said, some customer reviewers are extremely upset by the fact that replacement bulbs are expensive and must be obtained directly from the manufacturer. We are sympathetic to their indignation. However, considering that the feature is of dubious efficacy in the first place, 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.
If the Honeywell is out of stock, the Sunpentown SU-9210 Digital Evaporative Humidifier 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 puddling, and general inability to overhumidify. But it’s not nearly as easy to clean as our top pick, 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 one to 10 hours. Consumer Reports (subscription required) also likes it, giving it a recommendation and a score of 80 versus a 74 for the Honeywell HCM-350.
As far as quantitative testing goes, the Sunpentown SU-9210 kept right up with the Honeywell. Its 47.8-decibel sound level was right in line with the Honeywell’s 48.9 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 economics, the SU-9210’s total estimated operating cost of about $200 makes it cheaper than the Honeywell over the course of three years (wicks are two for about $20).
But the SU-9210 provides a worse overall user experience. Though the Honeywell is specifically designed to be easy to clean, the SU-9210 has many of the typical humidifier design flaws. The hand-wash-only reservoir is made of several plastic pieces fused together, and we’d worry about these leaking over time. It also 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.
The Sunpentown SU-4010 Dual Mist Humidifier with ION Exchange Filter 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, this is your best bet. Harry found it more effective than the Honeywell in a large bedroom, but he found it can overhumidify the space on higher settings.
Consumer Reports (subscription required) 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, 7½ pounds) makes it a good choice for anyone short on table space—it’ll fit on a bookshelf. 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. A Sweethome editor who owns this one has to clean it out with a 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 for refilling. Same goes for the tank lid, even if you overtighten it, which is easy to do.
The Venta Airwasher LW25 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 refills and cleanings. Though your typical humidifier should be cleaned about every third day, Venta recommends cleaning only every 10 to 14 days and relies on a proprietary chemical mixture to keep funk down between cleanings. A two-week supply (3.5 ounces) is included with the LW25, and the replacement bottle holds 35 ounces, so it’s good for more than four months of use. Additional bottles will run you about $20.
The Venta works by drawing air over a set of slowly rotating discs. It’s incredibly energy efficient, drawing seven watts on high, yet effective at humidifying, despite using only 0.2 gallons 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). 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 (see our section on health risks for more on these) 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.
It’s compact at 12 by 12 by 13 inches and 8.5 pounds, and it’s definitely a better choice than the other air washer we looked at made by Winix, which cost $20 more, had a more complicated user interface, and used 0.58 gallons per day (nearly three times as much as the Venta). The Winix also used an inferior disk design that required the disks to be inserted only one way. The cover was similarly unidirectional. The Venta’s symmetric design avoids these drawbacks.
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 three-ounce dose of its water treatment additive. Every six months, do a deep clean by filling the reservoir, adding Venta’s cleaner, and running on low for two hours, followed by rinsing with warm water as usual.
Despite its high sticker price and the 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 about $425 total (sticker price plus maintenance costs), it’s the second most expensive, but an impossibly low electricity cost of just $15 makes it a lot more affordable than you might expect.
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. For reference, a HEPA-certified air purifier would bring this number down to virtually zero in less than half an hour.
The Vicks Warm Mist V750 performed above average in our testing in the fall of 2015, raising the humidity levels from 60 to 82.5 percent over a three-hour period. It is clearly built to a price point, with cheap-feeling plastic and wobbly assembly. But hey, it’s cheap. Compared with its sister model, the Honeywell HWM705B Filter Free Warm Moisture Humidifier, it is slightly more solid and the outside got less hot.
The Vicks is compact (10½ by 12½ by 5¼ inches and a feathery 3½ pounds). It has a 1-gallon tank with a comfortable handle and a mixing chamber that draws room air in to mix with the hot steam, so the moisture exiting is warm, not hot. A medicine cup allows you to add medications or essential oils. Operation is simple, via a two-setting switch with an unobtrusive night-light indicating water status: green during operation, and red when it has shut off after emptying the tank. We tested the humidifier on high (1.9 gallons per day), where the 1-gallon tank needs to be refilled every 12 hours. It features an auto shut-off (as do all steam models we tested). One note of concern: We’ve seen several reports of leaks occurring at any time from a couple of weeks to a year after purchase, but those reports constitute less than 10 percent of the reviews. Still, to be safe, you could place the humidifier on spacers inside a plastic tub to catch any sudden leaks.
Warm-mist humidifiers work by heating water until it turns to steam. And that means they have the potential to cause burns—both from the hot water and steam and from the heating element. Because of that risk, the American Academy of Pediatrics recommends against their use in homes with children. (Note: The Stadler Form Fred, which we tested, was a particularly bad offender: Its silvery plastic steam-tube became extremely hot when the unit was on.)
People seem to like warm-mist humidifiers for four reasons: because they believe they “work better,” because they “feel better,” because they can diffuse essential oils, and because the steaming process kills germs. Point one is simply untrue: Warm-mist humidifiers are no better or worse than other types at humidifying the air. Point two is subjective, but in our tests we noticed no difference. Point three is true, but you don’t need a humidifier to diffuse essential oils; you just need a wick, a heater, and/or a fan. Point four may or may not be true, but contaminants in the humidifier itself may be the bigger risk anyway.
Then there’s the matter of energy usage and cost. Warm-mist humidifiers slightly heat the room in which they are used, meaning the thermostat could be turned down a pinch. The other types of humidifiers add water vapor to the air via evaporation, leading to a slight cooling of the air in the room, which will need to be heated again (via a furnace or other heating system).
But do warm-mist humidifiers offset their energy costs by lowering your heating bill? To quantify this, I did a back-of-the-envelope calculation. The humidifier is used for three years (for six months each year) and dispenses 4 liters of water per day of use. The house is heated with natural gas. For energy costs, I used my local California rates of 18¢ per kWh for electricity and $1.20 per therm for gas. The efficiency of both the electric humidifier (range 65 to 80 percent) and gas furnace was 80 percent (range 78 to 97 percent).
By figuring out the energy needed to heat the water from room temperature to near boiling (334 Joules), and adding the extra energy needed to vaporize it (2,260 Joules), we know the total energy (2,594 Joules) need per gram of water. Using the assumptions above, if you heat that water with the humidifier, you will spend a whopping $355 in electricity versus just $81 in natural gas to supply the same amount of heat to your air.
Cleaning a humidifier isn’t only about keeping it smelling fresh. It’s about your health. Left uncleaned, humidifiers can quickly become breeding grounds for numerous species of bacteria, amoebae, and fungi that trigger allergies, low-grade fevers, and, in the worst cases, a dangerous inflammation of the lungs called hypersensitivity pneumonitis. This happens so often that it even has a nickname: humidifier lung.
Wirecutter editor Tim Barribeau has firsthand experience. He said:
We were bad humidifier parents, and definitely weren’t cleaning the thing out as often as we were meant to—sometimes more than a week or two between cleaning. And even worse, I’m pretty sure on more than one occasion water just sat inside it for days at a time. But one dry night in winter, we turned on our adorable penguin-shaped humidifier. And the next morning, both my now-wife-then-girlfriend and I woke up feeling like we were dying. We both had incredibly tight chests where we couldn’t get in enough air to breathe properly, accompanied by constant coughing fits and tunnel vision. We assumed we’d both come down with some sort of weird chest cold, and tried to ride it out for a couple of days—and kept using the humidifier the entire time. Thankfully, I’m married to a doctor, and she started researching, and figured out we had humidifier lung. We got that thing out of the bedroom, I ran it through a couple of bleach water cycles, and we cleared up pretty quickly. But we both thought we had caught something pretty serious before she figured it out.
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 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). After the vinegar descaling step, rinse all surfaces with either one teaspoon of bleach mixed with a gallon of water or a three-percent hydrogen peroxide solution to disinfect, and then wipe dry.
Follow manufacturer recommendations for your cleaning products. Soap 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. And don’t improvise or “improve” manufacturer recommendations. As an example of why not to, certain cleaners have caused a public-health crisis in South Korea.
On evaporative humidifiers, you will need to perform occasional wick maintenance. 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, pull out the filter and let it dry when you turn the humidifier off for more than a day, or leave it in and let the fan run with no water until the filter is 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 the company recommends swapping out every six months.
As for the air washers, Venta recommends refilling water daily to keep the reservoir nearly full, so the rotating disks will be fully saturated, 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 the housing and fan blade with a cloth, then fill and add a dose of 3½ ounces of the company’s water treatment additive.
Note: The additive contains quaternary ammonium cations, or quats, a broad class of disinfectants that have been widely employed for decades. Quats have been linked with increased incidence of asthma, but the conditions that elevate that risk—skin contact, high concentrations, the presence of other cleaning agents, and inhalation of aerosolized quats—are unlikely to occur here. In particular, because quats are nonvolatile and the Venta is an evaporative humidifier, very little vaporization or aerosolization of the additive will occur. Quats are also linked with the development of resistant bacteria and other pathogens; given their heavy use industrially and commercially, the impact of the small quantities used in the Venta is probably inconsequential.
Every six months, do a deep clean by filling the reservoir, adding Venta’s cleaner, and running on low for two hours, followed by rinsing with warm water as usual. To give the housing a thorough cleaning, disassemble the upper housing (no tools required) and wipe the surfaces with a damp cloth.
In 2014, testing was performed in John’s 160-square-foot office with standard eight-foot ceilings. He lives in Southern California in a 1960s house that is typical of the era in that it is pretty leaky, compared with the tighter construction of new homes built with the newfangled concept of energy efficiency.
We tested the machines on five factors: noise, maximum humidification achievable, ability to hold a fixed humidity level (a way of evaluating the humidistat, if a model came with one), daily water consumption, and cost over time. For air washers, we also measured their actual ability to remove particles from the air.
Sound-pressure levels of each unit running on high and measured at a distance of 1 meter away and ½ meter above the ground. We took measurements with an iPhone 5s running the 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 decibels, about the highest that would not interfere with normal conversation (60 decibels), was used as a limit. For reference, a quiet office is 40 decibels, moderate rainfall is 50 decibels, and normal conversation is around 60 decibels. In another category of appliances where noise is a concern—dishwashers—anything 50 decibels and below is considered to be in the “quietest” category, and any machine below 45 decibels is considered practically silent.
Two humidifiers failed this test. The worst offender was the Stadler Form Hera, which came in at a painfully loud 74 decibels. We suspect it was a defective unit, as there is no reason for an ultrasonic humidifier to make this kind of racket. (The other ultrasonic models were nearly silent, less than 40 decibels.) The Vornado Evap2 came in at 59 decibels, but we kept it in the testing because it has an auto setting that adjusts the fan speed as necessary to maintain humidity.
Using testing conditions of 22 C +/- 0.7 degrees, and average starting humidity 48.1 +/- 7.1 percent, we filled the humidifiers with two liters of tap water and ran them for three hours on their highest setting. We measured temperature and humidity levels every 15 seconds using two Lascar high-accuracy USB data loggers. (They have a temperature accuracy of +/- 1 degree, and humidity accuracy of +/- 2 percent.) 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. The sensors had good agreement, except for with some of the ultrasonic humidifiers when the humidity near the unit was 5 to 10 percent higher. For our purposes, the values were averaged.
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 (34 percent), but it made a sopping-wet mess on the floor in the process. In a series of tests, the Honeywell brought the humidity up 14 percent, from 50 to 64 percent, with no condensation on the floor. Another test in a slightly smaller room (120 square feet) saw it raise the humidity from a very dry 22 percent humidity to a moist 64.5 percent in three hours. That’s solid, middle-of-the-pack performance.
We learned a bit more from the test. First, all the units were effective at increasing the humidity, generally from a comfortable 50 percent to a moist 65 percent or so. This is higher than recommended, yet still pleasant. Second, 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 moisture to your air. That’s because evaporative models are inherently self-regulating: The evaporative process slows down the moister the air gets. By contrast, because they work by physically injecting mist into the air, ultrasonic models have an ability to overhumidify and make a mess on the floor.
Humidity holding (humidistat accuracy)
We evaluated the humidifiers 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. (For machines with a humidistat, this is also a test of how accurate the humidistat really is. Our main pick, the Honeywell HCM-350, does not have a humidistat.)
All the evaporative and steam models reached and held humidities in the 60 to 65 percent range, even without a humidistat. This test revealed that the budget humidistats built into some models are not consistently up to the task, and even among humidifiers from the same manufacturer the quality of the humidistats was inconsistent.
The units generally put out between 1.1 and 2.4 gallons of moisture per day, or generally about 75 percent of the manufacturers’ claims. The air washers, 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 worried about it having enough oomph, yet it performed well on the maximum-humidification test, raising humidity levels 21.8 percent over three hours.
We calculated the cost of ownership over an expected product lifetime of three years, running 24 hours a day for six months a year. We measured the humidifiers’ power consumption 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 John’s area of 0.15396 ($/kWh). Consumables can include wick filters, demineralization cartridges, and antimicrobial silver cartridges.
Do air washers really wash the air?
For air washers, which claim to remove particles from the air, we measured airborne-particle concentrations at the beginning of the test and after three hours of running the machines. We used a laboratory-quality benchtop 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 actually rise for the Winix.
The Venta lowered the particle concentration from a starting concentration of 180 to a final 9 particles/cm³. The performance is good, but not nearly as good as the air purifiers tested for our best air purifier guide, but it’s 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.
The Winix, however, didn’t reduce particle counts at all. The counts started at 70 and climbed to 150 particles/cm³ after three hours. In 2008, Consumer Reports evaluated the Venta’s ability to remove much smaller particles (0.1 to 3 microns) and found it ineffective. Our take is that air washers and humidifiers can remove some larger particles (0.5 to 20 microns) like pollen and dust mites, but not nearly as well as a dedicated air purifier.
Functionally, the Sunpentown SU-2020 (2016 update) resembles our pick for larger spaces, the SU-4010. It differs chiefly in having a 2-gallon tank, twice the size of the SU-4010’s. Although the higher capacity is tempting, it means a full tank weighs over 16 pounds—a lot to lug around, especially if your sink is far from the humidifier. The big tank also gives it a larger footprint, 8.5 by 12.5 by 14 inches, versus 5 by 13 by 12 inches. That makes it harder to place on a bookshelf or side table—a potential problem, because elevating ultrasonic humidifiers is recommended to help the mist evaporate before it falls to the floor and puddles. And indeed, most complaints about the SU-2020 focus on that issue exactly: the mist condensing on floors, rugs, or furniture, often causing damage.
The Aircare MA0800 (2016 update) is an evaporative humidifier, like our main pick and runner-up. Aircare claims the MA0800 will humidify a space as large as 2,600 square feet. That, to be blunt, is doubtful, and many owners hoping to humidify their whole home with a single unit note that they’ve been disappointed. It gets high marks for durability and its ability to humidify large, though more reasonable, spaces. It’s a big machine, 12 inches deep, 18 wide, and 16½ high—not something you can tuck away on a shelf. It has a large 2.5-gallon tank that weighs more than 20 pounds when full; on the plus side, the manufacturer claims a potential 8 gallons of moisture output per day, which is very high. We’ll likely call one in for the next test, as a “large room” contender; we missed it until now because it’s advertised as a whole-house or “console” humidifier.
On its face, the Pure Enrichment Ultrasonic Cool-Mist Humidifier (2016 update) sure seems popular. But despite its high star rating on Amazon, the authenticity of many of those reviews is questionable. Besides that, its tiny 1½-liter tank means it’s useless for all but the smallest spaces—maybe 125 square feet, a 10-by-12 room. Its (seemingly authentic) negative reviews focus on two other disqualifying factors: It tips over easily, and when it tips, the tank has a tendency to break.
The Opolar 3.8-liter Ultrasonic Humidifier (2016 update) is intriguing because of its wide fill hole, which the manufacturer claims makes it easier to clean. Cleaning humidifiers is vitally important—see Health risks of a dirty humidifier, above—and our main pick’s ease of cleaning is key to our endorsement of it. Otherwise, however, this is a standard-issue ultrasonic humidifier, and in spite of its higher price, it offers no clear advantages over our ultrasonic pick, the Sunpentown SU-4010.
If you must have a budget-friendly ultrasonic, the Safety 1st Ultrasonic 360° Humidifier works, which is impressive for such a cheap unit, but its drawbacks keep it from being a pick. It’s not a bad deal for its currently price of about $30, but you’re going to get only that much worth of humidifier. 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 customer reviews that complain about leaking and other problems.
The Air-O-Swiss 7135 was an earlier 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 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 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. Plus, its humidistat completely failed to maintain a consistent level.
The Winix Air Washer was effective at humidifying, but had no effect at removing particles and did little to justify its exorbitant price tag. Though it uses the same basic technology as the Venta, its design made it more difficult to use. The base reservoir was not symmetric, and we had to insert the setup disks in the correct orientation.
The Sunpentown SU-3600 Digital Ultrasonic Humidifier with Humidistat is a Sunpentown humidifier that crams a fairly capable machine into a compact, stylish package that would fit on most nightstands. We liked the small size, and it’s nice that the 1-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.
The Stadler Form Hera is billed as a top-shelf unit, with warm and cool ultrasonic mists and bidirectional nozzles, a humidistat, and a night mode that automatically dims the display. But our unit generated excessive screeching noise measured at 74 decibels! The humidifier put out mist, but was so loud that we aborted our tests. It’s well-reviewed at Allergy Buyers Club, and we 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 Stadler Form Fred steam humidifier is either sleek and modern, or an ugly alien saucer/mini charcoal grill. It has a 2-gallon reservoir that’s good for all day on high. Controls are simple to use, though quite small: a power button, high-low button, and rotary knob for moisture output. When assembling, your hand gets pinched when installing the reservoir, and the lid is slightly difficult to align. The vent gets very hot during operation, and points toward the back, so you can’t put it close to a wall. Finally, during testing, the output rate varied widely, from 1.0 to 1.9 gallons per day. We cannot recommend it, even if you love its looks.
The Honeywell HWM705B Filter Free Warm Moisture Humidifier is nearly identical to the Vicks. Both are made by Kaz. The Honeywell was more flimsy and the outside got hotter to the touch. Despite consuming the same amount of energy (~230 W), it raised the RH only 15.5 percent, from 55.5 to 71 percent, during our three-hour test. Only choose this model if you must have black.
The Optimus Coolmist Ultrasonic Humidifier is a well-reviewed, bare-bones ultrasonic model with simple dial control and strong 2-gallon-per-day output. We found the output rate high, but extremely variable at 1.0 to 2.1 gallons per day (both on the high setting). The reservoir is a bit small at 1.11 gallons. It contains non-replaceable ceramic filters that will do little to trap minerals and prevent white dust.
Dyson’s AM10 is a uniquely shaped ultrasonic humidifier that builds on their earlier fan models. We wondered what you might get for spending as much as possible for a humidifier. The biggest difference from a basic ultrasonic model to one that costs much more is that it has a powerful fan to force the water droplets out through the oval opening. We found it solidly constructed and attractively designed and, well, different. Though not necessarily in a good way. For instance, you have to remove the oval portion before accessing the water reservoir. That’s an extra step. The tank’s fill hole is quite small, about the size of a quarter, making it more difficult to fill and harder to turn the knob to seal. Control is possible only via the remote, and the display is quite small and dimly lit. It performed well, ranking first on ability to hold relative humidity at a set point (average 1.4 percent RH over the set point, and 0.8 percent RH standard deviation), and third on humidity change (25.5 percent RH). Dyson definitely makes a statement with its design, but it fails to deliver value. Save your $500 to spend or invest elsewhere.
The Vornado Evap3 is a very attractive model. It aced the humidity-hold test, reaching the steadiest value among evaporative models, 3.6 percent over the set point and 1.0 percent standard deviation. It has a moderate 1½-gallon tank and high output of 2.7 gallons per day. It uses two wicking filters that last for four to eight weeks before they need to be replaced, at a cost of $12. Operating modes are high, low, or auto, with a built-in humidistat with values ranging from 35 to 60 percent RH, or continuous operation. Unfortunately, it’s a little bit loud on high (54 decibels), just making our 55-decibel cutoff, and the fill cap is really hard to turn.
The Vornado Evap2 is a promising humidifier and the little version of the Evap3 model. It uses a single wicking filter. It also performed well on the humidity hold, coming in second among evaporative models. But it’s too loud (59 decibels), and inserting the reservoir is too awkward. Aligning the base is also tricky as it has to come in at an angle, and we found ourselves struggling each time we refilled.
|Air-O-Swiss 7142||860||Ultrasonic||Low rating on Amazon. It’s highly rated when new at Top Ten Reviews 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 Air-O-Swiss 7135. Amazon reviewers report that failure over time, dying just after a year, poor customer service, inaccurate humidistat.|
|Air-O-Swiss 7144||650||Ultrasonic||Not very different from other Air-O-Swiss models, and smaller reservoir.|
|Air-O-Swiss 7147||650||Ultrasonic||Smaller reservoir than 7135, not as efficient in previous Wirecutter tests.|
|Bionaire Ultrasonic Filter-Free Tower Humidifier||Medium||Ultrasonic||Not much info to evaluate.|
|Crane Cool Mist Humidifier||250||Ultrasonic||During previous Wirecutter testing, the output was extremely low (0.5 gallons per day).|
|Crane Cube 0.5 Gal. Ultrasonic Cool Mist Humidifier||250||Ultrasonic||Tiny ½-gallon reservoir.|
|Crane Germ Defense EE-8064||500||Ultrasonic||Consumer Reports noted similar to EE-8065, but $40 more expensive.|
|Crane Germ Defense EE-8065||500||Ultrasonic||Decent unit recommended by Consumer Reports, but the indicator lights are super bright.|
|Crane Owl||250||Ultrasonic||Too small, and though rated to 250 square feet, its output is only 1.4 gallons. Cute animals are not a good fit for everyone.|
|Essick MA1201||2,500||Evaporative||Whole-house unit that’s too big for most people, but excellent value.|
|Holmes Smart Humidifier with WeMo||2,500||Evaporative||Whole-house unit, much bigger model than we’re considering.|
|HoMedics UHE-CM25||100||Ultrasonic||Too small, only rated to 100 square feet.|
|HoMedics UHE-CM45||100||Ultrasonic||Too small, only rated to 100 square feet.|
|Honeywell HCM-300T||1,050||Evaporative||Rated for bigger area that’s greater than 650 square feet.|
|Honeywell HCM-6009||1,900||Evaporative||Whole-house console unit, much bigger than other models in this survey.|
|Honeywell HCM-6011G Humidifier Quietcare Cool Mist Humidifier||2,300||Evaporative||Whole-house unit. Too big.|
|Honeywell HUT-300||400||Ultrasonic||Reviews on Amazon indicate it is hard to clean, and the reservoir is small (0.8 gallon) reservoir.|
|Honeywell HWM-340W||600||Vaporizer||Warm mist only, 400 watts to operate!|
|Honeywell Mistmate||150||Ultrasonic||Too small, only rated to 150 square feet.|
|Honeywell HWM 450||1,400||Heated||Ruled out from negative Amazon reviews of unit burning itself out.|
|Pure Guardian 0.2 Gal. Ultrasonic Cool Mist Humidifier||125||Ultrasonic||Too small, only rated to 125 square feet.|
|Pure Guardian Elite 1.3 Gal. Ultrasonic Humidifier||300||Ultrasonic||Pricey for room size.|
|Stadler Form William||1,000||Evaporative||High cost and rated at more than 1,000 square feet.|
|Vicks V3100||Small-medium||Evaporative||1.2 gallons per day too low an output.|
|Vicks V5100NS||400||Ultrasonic||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.|