Fiberglass and Other Flame-Resistant Fibers in Mattress Covers

Public complaints had raised concerns that some mattresses could release fiberglass into the air. To learn what mattress covers are made of, three California Department of Public Health scientists bought 4 new mattresses and cut samples from each layer of each cover (Wagner et al., 2022).

They identified the fibers with three kinds of microscope analysis: polarized light microscopy, scanning electron microscopy with X-ray analysis of the elements, and infrared microspectroscopy. The work focused on the cover layers, not the foam. The team did not measure fiberglass in room air. The authors say that more tests of fiber shedding in real homes, combined with air measurements, are needed (full paper).

Two of the four mattress covers had over 50% fiberglass in their inner sock layers. Up to 1% of that fiberglass had moved into the fabric layers next to it. The authors call this a possible risk of exposure if the zipper on the outer cover is opened. No fiberglass was seen on the outer surfaces of the brand new mattresses (Wagner et al., 2022).

The fiberglass fragments measured 30 to 50 micrometres in aerodynamic diameter, a measure of how particles move in air. The authors say fragments this size could be breathed into the nose, mouth and throat, but are likely too large to reach deeper into the lungs. The sock layers also held flame-resistant synthetic fibers that matched modacrylic containing vinyl chloride and antimony.

The authors also found that "chemical-free" certifications do not seem to cover mattress covers. They say mattress labels and shopper education need to improve (full paper).

Some mattress makers use fire barriers that contain no fiberglass. One common type is sold as hydrated silica. Bear, a mattress maker, describes its barrier fabric as "a blend of non-woven hydrated silica, rayon, polyester, and cotton" and states that "hydrated silica is not fiberglass" (Bear). That is the maker's own description. The Wagner study did not test hydrated silica barriers, and Nappedia has not found an independent study of how much these barriers shed.

California's Assembly Bill 1059 became law in October 2023. Starting 1 January 2027, it bars anyone from making, selling or distributing a new mattress, upholstered furniture or juvenile product in California that contains textile fiberglass. The law defines textile fiberglass as yarn made with one or more continuous glass filaments for knitting or weaving into fabric. Thread used to stitch mattress parts, and yarn in which the glass filaments are corespun or sheathed by another fiber, are excluded (AB 1059 bill text).

What to check: The fire barrier, at any firmness.

Read the law label and the product page for the fire barrier material. If you want to avoid fiberglass, skip any mattress that lists glass fiber, glass wool or glass filament. If your mattress already has a zippered cover, leave it closed.

• Standard for the Flammability (Open Flame) of Mattress SetsMattress Fire Rule
• Oz et al. (Environ. Sci. Technol. 2019)Foam Emissions and Indoor Air
• Arbes et al. (J. Allergy Clin. Immunol. 2003)Allergies & Dust Mites
• Browse all 26 studies in the research library