Editing Memory foam (section)

== Mattresses ==

A memory foam mattress is usually denser than other foam mattresses, making it both more supportive and heavier. Memory foam mattresses are often sold for higher prices than traditional mattresses. Memory foam used in mattresses is commonly manufactured in densities ranging from less than 24kg/m<sup>3</sup> (1.5&nbsp;lb/ft<sup>3</sup>) to 128kg/m<sup>3</sup> (8&nbsp;lb/ft<sup>3</sup>) density. Most standard memory foam has a density of 16–80&nbsp;kg/m<sup>3</sup> (1 to 5&nbsp;lb/ft<sup>3</sup>). Most bedding, such as topper pads and comfort layers in mattresses, has a density of 48–72&nbsp;kg/m<sup>3</sup> (3 to 4.5&nbsp;lb/ft<sup>3</sup>). High densities such as 85&nbsp;kg/m<sup>3</sup> (5.3&nbsp;lb/ft<sup>3</sup>) are used infrequently.

The firmness property (hard to soft) of memory foam is used in determining comfort. It is measured by a foam's [[indentation force deflection]] (IFD) rating. However, it is not a complete measurement of a "soft" or "firm" ''feel''. A foam of higher IFD but lower density can feel soft when compressed.

IFD measures the force in [[newton (unit)|newtons]] (or [[pounds-force]]) required to make a dent 1 inch into a foam sample {{convert|500|x|500|x|100|mm|abbr=on}} by a 323&nbsp;cm<sup>3</sup> (50 sq in, 8-inch-diameter) disc—known as IFD @ 25% compression.<ref>{{cite web|url=http://www.pfa.org/jifsg/jifsgs1.html|title=Polyurethane Foam Association|work=pfa.org|url-status=dead|archive-url=https://web.archive.org/web/20100104200333/http://www.pfa.org/jifsg/jifsgs1.html|archive-date=2010-01-04|access-date=2010-01-15}}</ref> IFD ratings for memory foams range between super soft (IFD 10) and semi-rigid (IFD 12). Most memory foam mattresses are firm (IFD 12 to IFD 16).

Second and third generation memory foams have an open-cell structure that reacts to body heat and weight by molding to the sleeper's body, helping relieve pressure points, preventing pressure sores, etc.<ref>{{cite web |last1=Strand |first1=Andrea |title=Memory Foam Mattresses Guide For Side Sleepers |url=https://eachnight.com/mattress-guides/best-mattress-for-side-sleepers/ |access-date=17 August 2018}}</ref>{{better|reason=commercial site|date=March 2022}} Manufacturers claim that this may help relieve pressure points to relieve pain and promote more restful sleep, although there are no objective studies supporting the mattresses' claimed benefits.<ref>{{cite web|author=Annie Stuart |title=Memory Foam Mattresses: Benefits and Disadvantages |url=https://www.webmd.com/sleep-disorders/features/memory-foam-pros-and-cons |date=2010-02-08 |publisher=WebMD}}</ref>

Memory foam mattresses retain body heat, so they can be excessively warm in hot weather.  However, gel-type memory foams tend to be cooler due to their greater breathability.<ref name=sfgate/>

=== Hazards ===
Emissions from memory foam mattresses may directly cause more respiratory irritation than other mattresses. Memory foam, like other [[polyurethane]] products, can be combustible.<ref>{{Cite web|title = Is Memory-Foam Bedding a Fire Risk?| date=11 September 2011 |url = http://www.goodhousekeeping.com/institute/a18314/gel-infused-memory-foam-bedding/|access-date = 2015-09-09|url-status = live|archive-url = https://web.archive.org/web/20150726055036/http://www.goodhousekeeping.com/institute/a18314/gel-infused-memory-foam-bedding/|archive-date = 2015-07-26}}</ref> Laws in several jurisdictions have been enacted to require that all bedding, including memory foam items, be resistant to ignition from an open flame such as a candle or cigarette lighter. US bedding laws that went into effect in 2010 change the Cal-117 Bulletin for FR testing.<ref>{{cite web|url=http://www.bhfti.ca.gov/about/laws/mat_standard.shtml|title=Federal Mattress Standard - Bureau of Home Furnishing and Thermal Insulation|work=ca.gov|url-status=dead|archive-url=https://web.archive.org/web/20080916001402/http://www.bhfti.ca.gov/about/laws/mat_standard.shtml|archive-date=2008-09-16}}</ref> 

There is concern that high levels of the fire retardant [[PBDE]] commonly used in memory foam could cause health problems for some users.<ref>Arlene Blum [http://www.sciencemag.org/cgi/content/full/318/5848/194b?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=fire+retardant+dilemma&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT The Fire Retardant Dilemma] {{webarchive|url=https://web.archive.org/web/20090605043201/http://www.sciencemag.org/cgi/content/full/318/5848/194b?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=fire+retardant+dilemma&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT |date=2009-06-05 }}. Science. 12 Oct 2007: 194b-195b.</ref> PBDEs are no longer used in most bedding foams, especially in the European Union.  

Manufacturers caution about leaving babies and small children unattended on memory foam mattresses, as they may find it difficult to turn over and may suffocate.<ref name=sfgate>{{cite web |url=https://homeguides.sfgate.com/memory-foam-dangers-100346.html |title=Memory Foam Dangers |website=SFGATE (website of the San Francisco Chronicle)|author=Laurie Brenner  |access-date= 13 May 2019}}</ref>

The [[United States Environmental Protection Agency]] published two documents proposing [[National Emissions Standards for Hazardous Air Pollutants]] (HAP) concerning hazardous emissions produced during the making of flexible [[polyurethane]] foam products.<ref>[http://www.epa.gov/ttn/atw/foam/fr1296.pdf Federal Register / Vol. 61, No. 250 / Friday, December 27, 1996 / Proposed Rule: Environmental Protection Agency] {{webarchive|url=https://web.archive.org/web/20120109160237/http://www.epa.gov/ttn/atw/foam/fr1296.pdf |date=January 9, 2012 }} and [http://www.epa.gov/ttn/atw/foam/fr1098.pdf Environmental Protection Agency] {{webarchive|url=https://web.archive.org/web/20120109160240/http://www.epa.gov/ttn/atw/foam/fr1098.pdf |date=2012-01-09 }} Federal Register / Vol. 63, No. 194 /Wednesday, October 7, 1998 /Rules and Regulations</ref> The HAP emissions associated with [[polyurethane]] foam production include [[methylene chloride]], [[toluene diisocyanate]], [[methyl chloroform]], [[methylene diphenyl diisocyanate]], [[propylene oxide]], [[diethanolamine]], [[methyl ethyl ketone]], [[methanol]], and [[toluene]]. However, not all chemical emissions associated with the production of these material have been classified. Methylene chloride makes up over 98 percent of the total HAP emissions from this industry. Short-term exposure to high concentrations of [[methylene chloride]] also irritates the nose and throat. The effects of chronic (long-term) exposure to methylene chloride in humans involve the central nervous system, and include headaches, dizziness, nausea, and memory loss. Animal studies indicate that inhalation of methylene chloride affects the liver, kidney, and cardiovascular system. Developmental or reproductive effects of methylene chloride have not been reported in humans, but limited animal studies have reported lowered fetal body weights in exposed rats.<ref>[http://www.epa.gov/ttn/atw/foam/fr1098.pdf Environmental Protection Agency] {{webarchive|url=https://web.archive.org/web/20120109160240/http://www.epa.gov/ttn/atw/foam/fr1098.pdf |date=2012-01-09 }} Federal Register / Vol. 63, No. 194 /Wednesday, October 7, 1998 /Rules and Regulations</ref>