Uploaded July 2026 | Updated September 2026, 2 weeks ago

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Introduced in the 1940s by the Mine Safety Appliances Company (MSA) of Pittsburgh, the ChemOx was a rebreather set intended for use by firefighters, mine rescuers, and other emergency personnel for working in unbreathable atmospheres. Instead of pressurized breathing gas cylinders, the unit used canisters of Potassium Superoxide (KO2) which reacts with carbon dioxide and moisture from the user’s breath to generate oxygen.

Thank you to the Fort la Reine Museum for loaning me this ChemOx unit: fortlareinemuseum.com

MSA Gas Mask video: youtu.be/i8XHV3CaBII
Tauchretter video: studio.youtube.com/video/5UGbkRPzNT8/edit

0:00 Introduction
1:10 Oxygen Rebreathers
3:00 Potassium Superoxide Reaction
4:31 Chlorate Candles
5:47 ChemOx External Features
7:07 U.S. Navy OBA Models
7:43 ChemOx Activation Procedure
9:20 Oxygen Timer
9:57 Relief Valve
10:23 Canister Disposal
11:12 Decline and Replacement
11:43 Outro

SOURCES

patents.google.com/patent/US2492272A/en?assignee=Mine+Safety+Appliances+Company&oq=Mine+Safety+Appliances+Company&sort=old&page=17

patents.google.com/patent/US2517209A/en?assignee=Mine+Safety+Appliances+Company&oq=Mine+Safety+Appliances+Company&sort=old&page=19

patents.google.com/patent/US2558756A/en?assignee=Mine+Safety+Appliances+Company&oq=Mine+Safety+Appliances+Company&sort=old&page=19

https://therebreathersite.nl/msa-chemox-since-1946/

web.archive.org/web/20070217223420/http://www.dcfp.navy.mil/library/dcnews/SCBACaseStudy.htm

firefightingincanada.com/50-years-of-scba-ffic-1235

scribd.com/document/469112472/Breathing-Apparatus#google_vignette

cdn.toxicdocs.org/Ne/NeOLjBY14md7JegZD6rLyB16Q/NeOLjBY14md7JegZD6rLyB16Q.pdf
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