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    Is wool really a natural flame retardant?

    by Spindle Mattress March 01, 2022 5 min read

    We received a great question from an owner of a Spindle mattress. She asked, "the founder and CEO of [named removed] Mattress said that the problem with the wool on top is that heat up the bed and keep our brain activity going and we are not resting. Also, he said that wool is not a fire retardant and the way to pass the test is have a chemical backing on it.  I am confused and I would like to know what is true in this, what can you tell me about this."

    We are not sure any of this can be substantiated. While we take them seriously, we can't be responsible for others' misleading or misunderstood comments. One great benefit of the internet is the wealth of information we have at our fingertips. It's also a curse. It's possible to find third-party validation of any of our deepest fears or wildest aspirations. It can be maddening, especially when buyer's remorse sets in. Disinformation campaigns are successful when they have enough truth to sound plausible mixed with the right among of clickbait-worthy content that makes us go hmmm...

    Is wool really flammable?

    One strand of the wool on fire myth can be traced to a misleading post on the interwebs. The hypothesis is substantiated when a match is applied to the bottom of a single thread of yarn dangled vertically. It burns. The challenge is that our mattress does not use a single strand of thread. It uses approximately 2 pounds per yard of wool batting which is compressed and quilted to organic cotton fabric. We do not use chemical flame retardants and the only fabric we use is organic cotton. Our mattress complies with federal fire safety laws -- CPSC fire safety reg 1633 -- by using natural wool as a flame barrier. It is not fireproof -- only resistant -- and only protects the mattress from catching on fire [within a certain timeframe]. We are not alone in using this type of construction. Many other mattress makers use a similar approach, though you'll need to check their websites to be sure. Those that quickly come to mind, and far from inclusive:

    • SleepEZ
    • Arizona Mattress
    • Sleep Essentials
    • Plush Beds
    • Flo Beds
    • Savvy Rest
    • OMI
    • Naturepedic
    • Cozy Pure
    • Shepherd's Dream
    • Berkeley Ergonomic
    • Sleeping Organic
    • Lifekind

    Of the commonly used fibers, wool has been widely consider a very good flame resistant material.  In fact, the military as well as police and firemen have been using wool for many centuries to reduce the risks associated with the dangers of being exposed to flames. There has been some movement away from wool fibres over the years to synthetics wool fibers can be 10 times or more expensive than synthetic options.

    Given the right conditions, all fibers will burn and there are many factors that influence how easily a fiber will ignite – such as the source of the ignition and conditions such as airflow and surrounding materials. The beauty behind wool is it is naturally flame resistant because its naturally high nitrogen and water content. Therefore, wool needs more oxygen/airflow or extremely flammable materials in the surrounding area for it to burn. Keep in mind that wool can ignite in the right circumstances like the single strand of wool example, but it normally won’t support a flame instead the wool’s cross-linked cell membrane structure will swell when heated to the point of combustion and form an insulating layer that prevents the flame from spreading. Even when it will not ignite, smouldering may occur for a short time after. In the end, wool is more difficult to ignite than other fibers. It must reach at least 570 degrees celsius before it will ignite.

    Fiber Limiting oxygen index (%) Heat of Combustion (KCAL/G) Ignition Temp (Celsius) Melting Temp (Celsius)
    Wool 25.2 4.9 570-600 Doesn't melt
    Cotton 18.4 3.9 255 Doesn't melt
    Nylon 20.1 7.9 485-575 160-260
    Polyester 20.6 5.7 485-560 252-292
    Rayon 19.7 3.9 420 Doesn't melt

    You can learn more about wool's flame-resistant qualities on the IWTO website.

    Also, these videos are good demonstrations of the flame resistant properties of wool.

    Wool heats up and increases brain activity?

    We are not medical experts and lack the insights this mattress CEO as gained from his research. I, however, welcome brain activity. The alternative is much less attractive. The topic drove us to the web to do some research. Of course, we came up with conflicting insights all around from what seem to be respectable sources. See:

    A Warm Bedtime Bath Can Help You Cool Down And Sleep Better [NPR] -- that natural cooling of the body's core temperature, apparently, may be a way to promote sleep

    Sleeping in Hot Rooms Bad for Brain [VOA & Harvard] -- great harm to the thinking ability of the study participants in rooms without air conditioning

    Why is it so difficult to sleep when it’s hot? [University of PA] - a big area of research has been looking at the relationship between sleep and learning and memory. We’ve learned that when you learn information during the day, it’s during sleep that new synaptic connections are solidified.

    The Effects of High-Temperature Weather on Human Sleep Quality and Appetite [U.S. National Library of Medicine] -- In this study, sleep quality and human appetite were adopted to study the quality of life in high-temperature weather

    Keep in mind that wool is renown for its temperature-regulating qualities as discussed in this Shepherd's Dream post. They are owned by the same family team that operates Woolgatherer Carding Mill, the provider of our Eco-wool.

    Regardless of the materials, it's not the mattress that's hot. It's us. Our bodies radiate heat and it's trapped by the materials in our bed. The conversation is usually around the latex...this is the first time we've been questioned about the wool. A latex mattress is theoretically cooler than memory foam, but you're still sleeping on 9" of foam and a gazillion air bubbles. When people report that they are hot sleepers -- as opposed to just being too warm in bed -- we suggest an innerspring mattress may be better. In those instances, no mattress will help. The person will be hot regardless of the mattress. The conundrum is you're not sure if it's you or the mattress. It can be both and.

    Other things that affect sleeping hot
    It's estimated one's mattress accounts for about 40% of our sleep experience. The temperature in bed can also be affected by

    • sheets -- textiles such as tencel, microfiber, linen, outlast, cool max and others are being used to help wick moisture away from the body and to dissipate heat...some brand names include: Sheex, Sleep Philosophy, West Elm, and others. This article from the Spruce and this one from NY Magazine may also help.
    • blankets + duvets -- using a duvet will trap body heat more effectively than only a blanket. changing what's on top of your mattress can help
    • pajamas -- hi-tech materials from athletics and hiking such as cool-core and dri-fit are all great at wicking moisture [we all sweat at night]. They can also be very effective in helping to dissipate heat.
    • insufficient hydration; alcohol intake; sleep hygiene; dreams; hormones; ambient temperature and more.

    It's not just about the bed. Sometimes a few simple adjustments, or a combination of a variety of changes, can make a big difference. Is latex a good option for you? We don't know.