Off-Gassing

New mattresses sometimes emit an odor during the off-gassing process, which is the result of volatile organic compounds (VOCs). VOCs are byproducts of mattress manufacturing. While they may smell bad, they’re generally considered harmless.

Off-gassing is especially common in mattress-in-a-box mattresses that are vacuum-sealed and packaged soon after production. Additionally, certain mattress materials are more prone to off-gassing odors than others.

Shopping around for a new mattress can take time, and if you trial different mattresses, that’s more time required for off-gassing. At the Test Lab, we try to take some of the guesswork out and provide product-tested recommendations.

We’ll cover what occurs during this process, who off-gassing affects, which materials are most likely to retain smells, and the scientific approach we use in our evaluations.

What is Off-Gassing?

Most new mattresses emit an initial odor known as off-gassing. Off-gassing occurs when you remove a mattress from its packaging for the first time. It is especially noticeable with mattress-in-a-box mattresses because vacuum sealing them traps chemical byproducts until you open the package in your home.

Off-gassing odors pose no known serious health risks, but they can be unpleasant. In the Test Lab, we measure the concentration of these odors in the room, relative to a control room, and study how long they last. Our assessments judge new mattresses on both the strength and persistence of their scents. A higher numerical rating means the new mattress smell is less severe and dissipates relatively quickly.

The term off-gassing typically refers to volatile organic compound (VOC) emissions. VOCs are a specific byproduct of the synthetic foam manufacturing process, so they’re most common in mattresses that contain polyfoam or memory foam. However, we also use the term off-gassing loosely to refer to any scent given off by a new mattress, topper, pillow, or other sleep product.

Who Should Care About Off-Gassing?

Off-gassing smells are unpleasant for most sleepers, but they may be more problematic for some than for others. If you’re especially sensitive to scents, a bed with strong off-gassing odors may cause unwanted symptoms, such as headaches, nausea, or dizziness. Individuals with respiratory issues, such as asthma or allergies, could also experience irritation of the airway and difficulty breathing.

However, off-gassing may not be a concern for those who don’t mind the smell or who have the time and space to allow the mattress to air out before use.

Mattress Materials and Off-Gassing

Off-gassing depends on materials. Synthetic substances, such as memory foam and polyfoam, are more prone to off-gassing than metal coils or natural materials. We’ll break down each major mattress material and its potential for off-gassing odor in more detail.

Off-Gassing by Mattress Type

Mattresses are typically categorized by the materials in the support core, which is a thick, sturdy layer that serves as the base. We’ll outline five of the most popular mattress types and discuss their performance in terms of off-gassing.

All-Foam: All-foam mattresses consist of a polyfoam support core with a comfort system made of memory foam, polyfoam, latex, or a combination of materials. Since most all-foam models use exclusively synthetic foam, they generally have a high potential for off-gassing.

Latex: Latex mattresses contain a support core and comfort system made from latex. Most models use natural latex, which should produce minimal odor due to its lack of chemical byproducts. That said, models with synthetic or blended latex may emit similar off-gassing odors to all-foam models.

Innerspring: Traditional innerspring mattresses include a bouncy core of metal springs with little surface padding. Once the dominant design in the mattress industry, innerspring models are becoming less common. This type of mattress is not prone to significant off-gassing because it uses little to no synthetic foam, and airflow through the coil system helps odors dissipate quickly.

Hybrid: A hybrid mattress contains a support core made from metal springs topped with a thick comfort system made from memory foam, polyfoam, latex, microcoils, or other materials. Thicker comfort systems generally enhance pressure relief and motion isolation compared to traditional innerspring models.

The overall level of off-gassing depends on a hybrid’s materials and construction. Ample layers of polyfoam or memory foam can increase off-gassing odors, while models that use natural latex comfort systems may have virtually no discernable scent. Most hybrids retain fewer off-gassing odors than the average all-foam model because of their reduced synthetic content and enhanced airflow.

Airbed: Airbeds use air chamber support units that can be emptied or filled to adjust the firmness level. Most also include a layer of memory foam or polyfoam as a comfort system. While the air chambers themselves may produce a slight odor, an airbed’s off-gassing potential is based primarily on the composition and thickness of its comfort layers.

How Do We Test for Off-Gassing?

We’ve developed a detailed methodology that we use to research, test, and review sleep products. For mattresses, this includes assigning an off-gassing rating. To generate a score that takes into account subjective and objective analyses, our testing team performs two tests: a smell test and a VOC test.

Body Test – Smell Test

The smell test is a subjective evaluation conducted by the testing team. With multiple team members in the room, we unbox the new mattress and place it on a bed frame. Each participant notes their initial impressions of the odor upon unboxing. We then check it again after 10 minutes, 1 hour, 3 hours, and 24 hours to record any changes, focusing on specific criteria:

• Strength of the odor
• What the odor smells like, including any recognizable qualities
• How far away the odor is detectable
• Perceived odors around the mattress and when smelling it directly

This assessment represents a realistic measure of how customers may experience off-gassing in their homes. A high score on this test indicates minimal perceivable odor that fades quickly.

To make this test as unbiased as possible, we institute controls, including reinforcing the bed base to prevent unnecessary movement, using the same testers each time, following consistent unboxing and storage protocols, and testing each model in the same space with equivalent ventilation and distance from the ground for the first 24 hours.

VOC Test

During this assessment, we measure the amount of VOCs given off during and after the unboxing process using a VOC meter. This test provides valuable data that allows us to more directly compare off-gassing performance between models.

Immediately after unboxing, we take readings on top of and around the mattress. When we perform the smell test detailed above, we also use the VOC meter to measure the air at the surface of the bed and in the surrounding area. We recheck at the 10-minute, 1-hour, 3-hour, and 24-hour marks.

For consistency across our evaluations, we measure the VOC content of the testing area before unboxing to establish a baseline and detect changes attributed to off-gassing. We also utilize the same VOC meter settings and positioning for every test, and we take measurements in the same locations using consistent methods.

Learn more about the Test Lab at the link below.