Investigation of ISS Fire Cartridge Catalyst Deactivation

Fire Cartridges are used with the emergency mask on the International Space Station for fire detection and post-fire cleanup activities. The cartridges include a layered design in which an activated carbon (AC) bed filters out acid gases and volatile organic compounds followed by a catalyst layer that oxidizes carbon monoxide. In 2020, verification testing of a new build of cartridges and subsequent surveillance testing of previously built fire cartridges showed unexpected degradation of the catalyst. An effort was undertaken to evaluate the cause of the degradation and to identify mitigations to prevent future loss of catalyst activity. The AC used in the cartridges was shown to cause a time-dependent reduction in CO oxidation catalyst activity, up to 95 days of exposure. Performing a thermal purge of the AC prior to catalyst exposure was shown to prevent loss of catalyst activity after 30 days of exposure. Additionally, the bulk of catalyst activity lost due to AC exposure was recovered by heating the catalyst to 300 °C in air. This paper describes the testing and analysis conducted to understand the source of catalyst deactivation and describes future activities to prevent recurrence.