The usual advice is to read your mattress law label and look for the words "glass fiber." That advice is worth following, but on its own it is not enough, and the reason is a detail of how the label is regulated.

California's Bureau of Household Goods and Services sets what a law label must say, and its official labeling requirements are specific: the label must describe "the kinds, types, and percentages of the filling material," listed in order of predominance by weight. Fiberglass in a mattress is usually not filling. It sits in the cover, woven into an inner sleeve around the foam. A label can be fully compliant and never mention it.

That is not a theory. When California Department of Public Health scientists bought four mattresses and cut them open, they found fiberglass in two of them, and on one of those two the label did not disclose it at all.

Here is what the label does cover, what the research actually found, how to check your own bed, and what changes when California's ban takes effect on January 1, 2027.

Start with the law label, but know what it leaves out

Read the law label first, because when fiberglass is disclosed, this is where it appears. The label is the white or off-white tag sewn into a seam, and under the California rules above it lists filling materials as percentages by weight, largest component first, using generic terms rather than brand names. Look for glass fiber, fiberglass, or glass wool. The California Department of Public Health notes in its factsheet on fiberglass and mattresses that fiberglass "may be called 'glass fiber' on a mattress label."

Then understand the limits, which CDPH states plainly in the same factsheet: "Some mattress labels do not list fiberglass even though fiberglass may be inside of the mattress." Their blunt summary is the one to hold onto: "You cannot know for sure if a mattress has fiberglass inside of it."

One more limit is worth knowing, because it catches people who thought they had already checked. CDPH points out that some mattresses carry a CertiPUR-US label, and that CertiPUR-US certifies the foam only. It does not certify the other materials inside a mattress, including the cover where fiberglass lives. A CertiPUR-US badge is not a fiberglass-free claim.

What researchers found when they cut open four mattresses

In a peer-reviewed study published in the International Journal of Environmental Research and Public Health, CDPH scientists bought four mattresses from common online outlets in April and May 2021 and analyzed the covers using polarized light microscopy, SEM-EDS and FTIR microspectroscopy. The full study is open access. Its findings are the most concrete evidence available on this question, and they cut in both directions.

What they found:

• Two of the four mattress covers contained over 50% fiberglass in their inner sock layers.
• Up to 1% of the fiberglass had migrated into adjacent fabric layers, which the authors describe as a potential exposure risk "if the zipper on the outer cover is opened."
• No fiberglass was observed on the brand new mattresses' outer surfaces. On an intact, unopened mattress, the fiberglass stayed where it was put.
• The fiberglass fragments had calculated aerodynamic diameters of 30 to 50 micrometres, which the authors note are "potentially inhalable into the nose, mouth, and throat, but are likely too large to penetrate deeper into the lungs."
• All four mattresses advertised CertiPUR-US certified foam. Two of them still contained fiberglass in the cover.

The labeling finding is the one that matters most for anyone checking their own bed. On the Zinus Green Tea 6 inch memory foam twin, fiberglass was disclosed, but not in the law label section, which the authors note "is required to specify filling materials only." On the Graco crib and toddler deluxe mattress, the presence of fiberglass "was not disclosed on the labels," which the authors say left consumers unaware of it.

The study also found that the synthetic fibers in the inner sock layers of two mattresses matched modacrylic containing vinyl chloride and antimony trioxide, and that in general the polymer fiber types in the covers were listed on the tags "but with no flame-retardant specification." The fibers are often named. What they are doing there is not.

Why fiberglass is in mattresses at all

Fiberglass is in some mattresses because every mattress sold in the United States has to pass two federal flammability tests, and a woven glass sleeve is an effective way to pass the harder one without using flame retardant chemicals.

16 CFR Part 1632 covers smouldering ignition. A lit cigarette is placed on the surface, and the resulting char must not extend more than 2 inches in any direction from the nearest point of the cigarette.

16 CFR Part 1633 covers open flame exposure across a 30 minute test, and sets two limits: peak heat release must not exceed 200 kilowatts at any point, and total heat release must not exceed 15 megajoules during the first 10 minutes.

CDPH puts the trade-off in one line: "Fiberglass is used instead of chemicals as a fire retardant." The National Capital Poison Center's overview of fiberglass in mattresses adds the useful context that fiberglass is a man-made mineral fiber made from silica sand, limestone, recycled glass and soda ash, and that it is durable and heat resistant, which is exactly why it works as a thermal barrier during a fire.

The failure mode is not the barrier doing its job. It is the barrier being opened. Both CDPH and the Poison Center describe exposure as something that happens when covers are unzipped, removed or torn, which matches the study's finding that new, intact mattresses had no fiberglass on their outer surfaces.

The other fire barriers, and what they look like on a tag

A mattress that passes the open flame standard without fiberglass is using one of several alternatives. The materials below are named either in the CDPH study or in California's own statute, so this list is grounded rather than generic.

Barrier material	How it shows up	Where it is documented
Textile fiberglass	"glass fiber", "fiberglass", "glass wool", sometimes absent	Found in 2 of 4 covers in the CDPH study
Modacrylic	"modacrylic", often with antimony trioxide	Identified in the sock layers of 2 mattresses in the study
Rayon or viscose	"rayon", "viscose"	Matched by FTIR in one mattress cover in the study
Aramid	"aramid", "Kevlar", "Nomex"	Named and exempted in California AB 1059
Wool	"wool"	Passes on the fiber's own properties

 

Wool is the one that is not a barrier added to fix a problem the core material created. According to the International Wool Textile Organisation, wool is difficult to ignite at 570 to 600 degrees Celsius, against 255 degrees for cotton and 485 to 560 degrees for polyester, and wool does not melt, where polyester melts at 252 to 292 degrees and nylon at 160 to 260 degrees. That is why a latex and wool construction can meet the same federal standard without a barrier sock in it.

One caution on the middle rows. Modacrylic is a flame retardant fiber, and the CDPH study detected antimony trioxide in the modacrylic it found. "Not fiberglass" and "no flame retardant chemistry" are two different claims, and a mattress can satisfy the first without satisfying the second.

How serious is the risk, stated proportionately

Fiberglass is an irritant, and the evidence does not support treating it as equivalent to asbestos. Both halves of that sentence matter.

On the irritant side, the CDPH study describes fiberglass as "a known respiratory, skin and eye irritant and an asthmagen." CDPH's factsheet is more concrete: contact can irritate the eyes and skin, and breathing in small fragments can irritate the nose, throat and lungs and cause breathing problems. The case that prompted their investigation involved a 6 year old child with persistent skin and respiratory irritation linked to suspected leakage from a mattress bought in 2018, and the cleanup required disposing of the mattress, the carpet and clothing from which fibers could not be removed. The study also records 128 complaints to the Consumer Product Safety Commission between 1 January and 31 December 2020 linked to fiberglass exposure across several mattress brands.

On the asbestos comparison, the International Agency for Research on Cancer reviewed the evidence and concluded in 2001 that continuous glass filament and insulation glass wool fall into Group 3, not classifiable as to carcinogenicity in humans. Asbestos is Group 1, carcinogenic to humans. The study notes this conclusion was supported by a further review of the occupational epidemiology literature in 2011, and that the fragments it measured were likely too large to reach the deep lung.

The honest summary: a sealed mattress is not exposing you, a released one is a genuine irritant problem and an expensive cleanup, and it is not a cancer scare.

What changes on January 1, 2027

California will prohibit the sale of any new mattress containing textile fiberglass from January 1, 2027. The law is AB 1059, and it was signed on October 8, 2023.

From that date, no person, "including, but not limited to, a manufacturer, retailer, importer, or online seller," may manufacture, sell, offer or distribute in commerce in California any new juvenile product, mattress or upholstered furniture that contains textile fiberglass, or a constituent component of which contains it. Custom upholsterers may not use replacement components containing it. Fines run from $1,000 to $2,500 for a first violation and $2,500 to $5,000 for a second.

The statute defines textile fiberglass as textile yarns whose composition includes one or more continuous glass filaments in a form suitable for knitting, weaving or otherwise intertwining to form a textile fabric. Two things are carved out: thread or fiber used for stitching mattress components together, and yarns in which the glass filaments are corespun or sheathed inside another fiber.

A second change lands the same day. California has capped covered flame retardant chemicals at 1,000 parts per million since January 2020, but components of adult mattresses other than foam were exempt. AB 1059 makes that exemption inoperative on January 1, 2027, extending the chemical limit to the whole mattress rather than only its foam. Aramid fiber used in fabric inside the mattress or on a non-sleep surface remains exempt, as does modacrylic fiber containing no antimony trioxide.

Two things this does not do. It places no obligation on mattresses already in your home, so nothing is recalled and nothing is replaced. And it takes effect on the date of sale, so a mattress bought in December 2026 is not covered by it.

What to do if you think your mattress has fiberglass

Leave the cover on. This is the first instruction in CDPH's guidance and the most important one, because it is the opposite of what most people want to do once they suspect something is in there. CDPH's wording is unambiguous: keep the outer cover sealed shut, and never unzip an outer mattress cover. A zipper is not permission. The study found three of its four mattresses had zippers on the outer cover, and it was opening that zipper the authors identified as the exposure route.

If the cover has a tear that cannot be repaired, CDPH advises getting rid of the mattress.

If you are not replacing it immediately, a fully enclosing protector adds a washable layer over the cover you have been told not to open. A GOTS certified organic cotton mattress protector does this without introducing vinyl, PVC, phthalates or PFAS, which matters if chemical exposure was the reason you started reading about this at all.

If fiberglass has already escaped, CDPH's cleanup guidance is specific and worth following exactly:

• Protect yourself. Wear eye goggles, a mask covering nose and mouth, and loose-fitting clothing that covers the skin.
• Remove the mattress, covering it first to reduce the spread of fibers.
• Use a vacuum with a HEPA filter, and do not sweep. Sweeping pushes fibers into the air. Wipe all surfaces with a damp cloth.
• Wash sheets, blankets and clothes separately from other laundry, rinsing the machine thoroughly after each wash. Discard items the fibers cannot be removed from.
• File a complaint with the Consumer Product Safety Commission at saferproducts.gov, which is also where CDPH directs people to search existing complaints by brand.

Four questions worth asking before you buy

Ask in writing and keep the reply. Because the label may not settle it, the manufacturer's own answer is the next best evidence.

• "Does this model contain any glass fiber or fiberglass in the fire barrier, the cover, or any internal component?" Naming the components matters, since the law label covers filling only.
• "What material is the fire barrier made from?" A brand using wool, rayon, modacrylic or aramid will answer immediately.
• "Will this model comply with California AB 1059 on January 1, 2027?" This asks about fiberglass without using the word, and it has a yes or no answer.
• "Does any certification you display cover the cover and fire barrier, or only the foam?" CDPH flags CertiPUR-US specifically as foam-only, and the study found all four of its test mattresses advertised it.

What certified organic mattresses use instead

Certified organic mattresses avoid the question by not building on a foam core that needs a glass barrier. A latex and wool construction meets the same federal open flame standard on the properties of the materials themselves, which is why GOTS and GOLS certified organic mattresses contain no fiberglass and no added flame retardant chemicals.

Read the certifications literally rather than as a general quality signal. GOTS governs the textiles and GOLS governs the latex, and each sets limits on what can be present in the certified product. We have written a fuller breakdown of what GOTS and GOLS cover if you want the detail.

The words "organic," "natural" and "eco-friendly" are not regulated terms on a mattress and none of them means fiberglass-free on their own. A certification scope and a materials list mean something. An adjective does not. That applies to how you read our pages as much as anyone else's.

Frequently asked questions

How do I know if my mattress has fiberglass?

Read the law label for "glass fiber," "fiberglass" or "glass wool," then ask the manufacturer directly, because the label lists filling materials only and mattress fiberglass usually sits in the cover. CDPH states that some labels do not list fiberglass even when it is present, and that you cannot know for certain from the label alone.

Is it safe to sleep on a mattress with fiberglass?

The risk comes from the barrier being opened rather than from sleeping on an intact mattress. CDPH researchers found no fiberglass on the outer surfaces of the new mattresses they tested, and identified opening the outer zipper as the exposure route.

Do all mattresses have fiberglass?

No. In the only published study of its kind, CDPH scientists found fiberglass in two of four mattresses they tested, and alternatives including wool, rayon, modacrylic and aramid are all in use. No agency publishes a comprehensive list of which models contain it.

Is fiberglass as bad as asbestos?

No. The International Agency for Research on Cancer classifies continuous glass filament as Group 3, not classifiable as to carcinogenicity in humans, while asbestos is Group 1, carcinogenic to humans. Fiberglass is an irritant and a difficult contaminant to clean up, which is a real problem of a different kind.

What are the symptoms of fiberglass exposure from a mattress?

CDPH reports that contact can irritate the eyes and skin, and that breathing in small fragments can irritate the nose, throat and lungs and cause breathing problems. The study describes fiberglass as a known respiratory, skin and eye irritant and an asthmagen.

Does a CertiPUR-US label mean my mattress has no fiberglass?

No. CDPH states that CertiPUR-US certifies the safety of the foam inside a mattress and does not certify other materials inside it. All four mattresses in the CDPH study advertised CertiPUR-US foam, and two of them contained fiberglass in the cover.

Can I unzip the cover to look for fiberglass?

No. CDPH advises never unzipping an outer mattress cover, and the study measured fiberglass migration into adjacent layers that would become an exposure route once the zipper is opened. If you need to know, ask the manufacturer instead.

Checking takes a minute, and asking takes one email

Pull back the fitted sheet, find the tag on the side seam, and read the filling percentages. If "glass fiber" is there, you have your answer. If it is not, you have ruled out one thing rather than all of them, and the next step is an email to the manufacturer naming the cover and the fire barrier specifically.

If that search turns into looking for a replacement, our sleep advisors can walk you through what is in each construction and what each certification actually covers. You can browse the organic mattress collection online, or visit one of our Bay Area showrooms in San Francisco, Burlingame, Los Altos, San Rafael or Walnut Creek, where you can open a cutaway sample and look at the layers yourself.