Editing Gas mask (section)

===Safety of old gas masks===
Gas masks have a useful lifespan limited by the absorbent capacity of the filter. Filters cease to provide protection when saturated with hazardous chemicals, and degrade over time even if sealed. Most gas masks have sealing caps over the air intake and are stored in vacuum-sealed bags to prevent the filter from degrading due to exposure to humidity and pollutants in normal air. Unused gas mask filters from World War II may not protect the wearer at all, and could be harmful if worn due to long-term changes in the chemical composition of the filter.{{Citation needed|date=November 2021}}
[[File:2 Gasmaskenfilter.jpg|thumb|An asbestos-containing Soviet GP-5 filter and a safe modern one in comparison.]]

Some World War II and Soviet Cold War gas mask filters contained [[chrysotile asbestos]] or [[Riebeckite#Crocidolite (fibrous riebeckite)|crocidolite asbestos]].<ref>{{Cite web|title=Porton Down report on the presence of asbestos in World War II respirator canisters|url=http://ibasecretariat.org/porton_down_rep_1989.pdf |archive-url=https://web.archive.org/web/20190502224759/http://ibasecretariat.org/porton_down_rep_1989.pdf |archive-date=2019-05-02 |url-status=live|page=2 (summary)}}</ref><ref>{{Cite news| last = Burns| first = Judith| title = Ban wartime gas masks, schools told| work = BBC News| access-date = August 21, 2018| date = May 13, 2014| url = https://www.bbc.com/news/education-27391955}}</ref><ref>{{Cite book| publisher = Springer Science & Business Media| isbn = 978-1-4612-2496-9| last1 = Dail| first1 = David H.| last2 = Hammar| first2 = Samuel P.| last3 = Colby| first3 = Thomas V.| title = Pulmonary Pathology — Tumors| date = December 6, 2012 |url=https://books.google.com/books?id=wSgyBwAAQBAJ&pg=PT1005}}</ref> not known to be harmful at the time. It is not reliably known for how long the materials were used in filters.

Typically, masks using 40&nbsp;mm connections are a more recent design. Rubber degrades with time, so boxed unused "modern type" masks can be [[ozone cracking|cracked]] and leak. The US C2 canister (black) contains [[hexavalent chromium]]; studies by the [[U.S. Army Chemical Corps]] found that the level in the filter was acceptable, but suggest caution when using, as it is a [[carcinogen]].<ref>{{Cite web|title=OPERATOR'S MANUAL
|url=http://chemicaldragon.com/yahoo_site_admin/assets/docs/TM_3-4240-342-10.12652555.pdf|access-date=2022-02-05|archive-url=https://web.archive.org/web/20160429130940/http://chemicaldragon.com/yahoo_site_admin/assets/docs/TM_3-4240-342-10.12652555.pdf|archive-date=2016-04-29}}</ref>