What is mattress off-gassing and can it be dangerous to your health?

Weird smell coming from your new mattress? It's actually very normal, here's why it happens and what you can do about it

Grey bedroom with striped headboard
(Image credit: Future)

So you've ordered your new mattress, it's been delivered with zero issues and you are just about to do the new mattress comfort test (lying down for ten minutes and trying not to fall asleep) and you notice your mattress is omitting a smell. This is totally normal, common in fact especially if you have ordered a mattress online and it's come in a box. It's a phenomenon known in the mattress world as off-gassing. 

Off-gassing is most common in mattresses that are vacuum-sealed and packaged quickly after production, with some materials being more prone to it than others. But Even the best mattresses on the market can emit an odor, which can be off-putting or even interrupt sleep if you’re particularly sensitive. 

But is it dangerous? Can you do anything about it? Or what should you look out for if you want to totally avoid it? Here we tell you everything you need to know about off-gassing...

What is mattress off-gassing?

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(Image credit: Future)

Off-gassing occurs when a mattress is unwrapped, with it being particularly prevalent with mattresses in a box where the vacuum sealing traps chemical by-products. What are these chemical by-products? They’re known as VOCs (volatile organic compounds. VOCs are a specific by-product of the synthetic foam manufacturing process, with them being more common with mattresses made with polyfoam or memory foam. VOCs come in lots of different forms, including benzene, acetone, formaldehyde, and ethanol, some have a stronger smell than others, or you might be more sensitive to certain VOCs.

How long does off-gassing last?

Although there are no absolutes when it comes to a new mattress smell, you can work out a rough estimation from the mattress’ composition (we’ll talk about that more in a minute). In general all-foam mattresses will take longer for off-gassing to dissipate than their hybrid mattress cousins. Off-gassing can fade within a couple of hours but may last several days. You may also be able to smell a faint trace for up to several weeks.

Is off gassing dangerous?

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(Image credit: Future)

Despite the unpleasant smell, VOCs do not possess any significant health risks and for most sleepers off-gassing is completely harmless. If you’re sensitive to strong odors you may suffer with some temporary symptoms, such as dizziness, nausea, or headaches. But this is rare and for most people, the smell itself is the most unpleasant thing. 

It’s worth taking a little more care with children though, who have a slightly heightened vulnerability due to their age and size. You might want to consider inflating a child’s mattress in another room before moving it to their bed to sleep on. Opening windows and getting fresh air into a room also helps to minimize exposure.

Do all new mattresses off-gas?

Mattresses are generally categorized by the materials that are used in the support core. This is the thick layer that serves as the base of the bed and gives your mattress stability. Some mattresses off-gas, and some are less likely to, let’s look at the most popular mattress types:

Memory foam mattress off-gassing

An all-foam mattress has a polyfoam support core, combined with comfort materials such as memory foam, polyfoam, or a combination of foam materials. Because all-foam mattresses use a combination of synthetic foam, they have the highest potential for off-gassing. Memory foam mattresses tend to emit the most noticeable odors, so look for mattresses with certifications from GREENGUARD Gold, OEKO-TEX, CertiPUR-US, or eco-INSTITUT as these are tested for emission standards. This should help to reduce the potential for severe off-gassing.

Grey bedroom with striped headboard

(Image credit: Future)

Latex mattresses and off-gassing

Latex mattresses use support cores and comfort materials made of latex. The best latex mattresses use natural latex, meaning you shouldn’t have any off-gassing with it being a natural product. However, synthetic, or blended latex can emit almost as much off-gassing as all-foam mattresses.

Hybrid mattresses and off-gassing

A hybrid mattress consists of a support core made from metal springs and comfort materials such as memory foam, latex, microcoils, polyfoam, and other materials. Off-gassing will depend on the hybrid mattress’ materials and construction. Layers of memory foam and polyfoam will emit more off-gassing odors, whereas natural latex won’t have any scent. There will be less off-gassing with an all-foam mattress due to the enhanced airflow and the lower use of synthetic materials.

Innerspring mattresses and off-gassing

Innerspring mattresses have a bouncy core of metal springs combined with comfort padding. These mattresses aren’t prone to off-gassing because they contain very little or no synthetic foam and the coils help to promote airflow that dissipates any smells.

How to reduce off-gassing when opening a mattress

Before you start open all the windows in the bedroom to get fresh air circulating. If there’s not a lot of breeze coming into your room, you can add in some fans to help move the air about. It’s also important that the bedroom is dry with no dampness, as dampness will help smells linger for longer. 

Remove all plastic packaging from your mattress as quickly as possible and get this out of the house immediately. Unroll the mattress fully so that it can start to inflate and is no longer compressed – the inflating of the mattress will also help to shift smells.

If the mattress is unbearably bad and it’s a dry day, you could consider airing the mattress outside to help odors dissipate quicker. Of course, the downside of this is that you have to lug a heavy mattress outside and then bring it back in and (usually) upstairs to a bedroom. 

Best mattresses for minimal off-gassing

Off-gassing FAQs

Is it safe to sleep on a new mattress?

In short yes, it's safe to sleep on a new mattress on the first night you have it. However, it might take up to a few weeks for it to settle – by that we mean some mattress need time to adjust to your body and soften, so don't be surprised if that first night's sleep is not as comfy as expected. 

Do bear in mind that some mattresses, although to would be safe to sleep on, are recommended to wait 24 hours to sleep on so they have time to expand. This is common with mattresses that have come rolled in a box.  

What's the best type of mattress to avid off-gassing?

Avoid synthetic foam mattresses as all of these will give off some level of smell. The best type of mattress to go for if you really want to avoid the smell (or limit it) are natural materials like natural latex or a sprung mattress.

Mattress off-gassing is a very common phenomenon when buying a new mattress, and even amazing quality mattresses can let off an odor when first opened. Usually, it's not dangerous to your health and is just an unpleasant smell that hangs around for a few hours. Just be sure to open up your mattress as quickly as possible after it arrives, and open the windows to help the small dissipate faster. 

Jo Plumridge

Jo Plumridge is a freelance writer and photographer with over 20 years of experience writing for a variety of magazines, websites and books. She writes, perhaps unsurprisingly, about photography, but also on all things interior design and sleep-related, alongside reviews of home and tech products. Jo loves exploring the latest design trends, although she’s yet to find a carpet that doesn’t show up the cat hair from the cats she and her husband foster.