Mmmmm, foam. It’s so tasty on the top of a latte. And so comfy in a mattress. All these new ordered-online, shipped-to-your-house mattresses are made of some kind of foam. They have to be, so they fit into that smallish box they’re shipped in.
Just like almost every other substance on the planet, polyurethane foam off-gasses, or releases compounds into the air. Yes, you breathe in these compounds when you sleep on these mattresses. But no, they’re not going to hurt you. Many of these compounds can be nasty and cause health problems in high volume, but the amounts your mattress exhales are pretty small, and they get even smaller over time. (Many other household sources, such as laminate flooring, emit these compounds.) The companies that make the mattresses we’ve tested and selected as the best at Sweethome have their polyurethane foam independently tested and verified by a company called CertiPUR-US to ensure that the amount their foam off-gasses is below CertiPUR-US’s standards. We’ll get to what comes off a new foam mattress and why in a minute, but first, let’s talk polymerization reactions.
Polyurethane foam comes in many different kinds, and it’s in tons of stuff. Flexible polyurethane foam, the kind that’s in online-ordered mattresses, is also in car upholstery, couches, kids’ car seats, home insulation, yadda yadda. It’s everywhere. You can make polyurethane foam pretty easily—generically, it’s the reaction between polyols (alcohols with multiple -OH groups) and diisocyanates. These two compounds come together to make urethane linkages and make long molecules that repeat over and over—poly (many) urethanes.
The compounds that float off polyurethane (and many other sources) are generally known as VOCs or volatile organic compounds—“volatile” meaning they float through the air easily, and “organic” as in they contain carbon (not “organic farming” organic). The EPA’s definition of a VOC is somewhat dizzying, and the agency doesn’t actually regulate VOCs in household products. The specific VOCs that can come off of foam mattress vary a lot: tiny amounts of unreacted polyol or diisocyanate, the catalyst 2-ethyl-hexanoic acid, or toluene. Many others can come off, as well. Different places or stages in making a mattress can introduce VOCs, and the VOCs can vary for each batch of foam.
CertiPUR-US tested the flexible polyurethane foam in all three of our mattress picks by letting the foam sit in a chamber for three days with air blowing over it, and then taking samples of the chamber’s air. CertiPUR-US has established standards for emissions and content for foam products, including an upper limit on total VOCs of 0.5 parts per million (ppm). CertiPUR-US’s technical document outlines this in great technical detail. (Note: Michael Crowell, CertiPUR-US’s executive director, pointed out to me several times in an email that CertiPUR-US does not test the whole mattress, just the polyurethane foam. It also doesn’t test latex foam, which is part of Casper’s mattresses.)
CertiPUR-US derives its limits “from a number of sources including the EPA, CPSC, REACH, and RoHS,” Crowell told me in an email.1 For example, a cube of polyurethane foam should not give off more than 0.16 ppm of benzene after 72 hours to get the CertiPUR-US seal.2 (For reference, OSHA’s benzene limit is 1 ppm over an eight-hour workday.) For toluene, another likely VOC, CertiPUR-US’s limit is 0.13 ppm (OSHA’s limit is 200 ppm over eight hours).
Our recent pick for the best online mattress for most people, the Leesa, is made of three foam layers, and the bottom two layers are polyurethane foam. The other two mattress picks, the Casper and the Tuft & Needle, are also mostly made of polyurethane foam; the Casper has a layer of latex foam on top. The foam in all three mattresses passed CertiPUR-US’s tests and have its seal of approval.
So, these VOC limits are for adults, but what about for infants? Sleeping with a baby on a mattress you desperately ordered online at 2 a.m. is certainly a thing. Babies spend many more hours a day sleeping and so have a larger window for potential exposure to VOCs, say the authors of a 2014 study on the VOCs emitted from crib mattresses. The study found that VOCs coming from polyurethane crib mattresses at room temperature were about the same level as VOCs coming from other indoor emitters, such as laminate flooring. Some studies have linked high levels of some VOCs, such as benzene and toluene, to increased risk of asthma and allergies in some young kids.
Keep in mind that CertiPUR-US’s limits for VOCs coming off of foam are basically after it let the foam air out for three days. If you have a vacuum-packed mattress shipped to you, you also can air it out. The authors of the crib mattress study measured the VOCs in new mattresses and in mattresses around five years old and found that the levels of VOCs in polyurethane foam do decrease over time. Kevin Purdy, who wrote the online mattress guide, told me that the mattresses did stink pretty consistently right after he took them out of their boxes. Kind of like a new car smell, he said. The smell was still quite strong after a day (like, smell it through the sheets strong), a lot less stinky by the second day, and pretty much gone by the third or fourth day. So maybe leaving your new mattress in a room with some airflow for a few days is a decent idea. Get rid of the stink, and probably some VOCs too. Can’t hurt.
When a source of light moves toward you, its waves are compressed and pushed to a higher energy. We can’t always see this blue shift, but it’s there.
In the space of Internet science, there’s a lot of bad information floating around. In this biweekly column, Leigh Krietsch Boerner, chemistry PhD and science editor of The Sweethome, will tell you what you need to know on the science of home products, and what’s all around you.
(Top photo by Jeremy Pavia, with illustration by Elizabeth Brown.)