347 SYSTEMS: ENVIRONMENTAL CONTROL AND LIFE SUPPORT SYSTEM—SUPPORTING THE HUMAN ELEMENT OF THE ISS CHAPTER 19 atmosphere, they can find themselves in a situation in which they do not have enough O 2 to maintain cognitive brain functions. If this occurs, they will don a PBA and isolate themselves in their return vehicle to prevent suffering from hypoxia—the result of not breathing enough O 2 . Figure 12. PBA (left) and respirator with fire cartridges (right). Different filters (orange boxes on either side) are attached to the respirator when it is being used after a fire or a toxic spill release such as ammonia. Toxic Atmosphere (ATM) represents the final emergency that the ECLSS supports, and which the ETHOS flight controller monitors. Various chemicals on the ISS are dangerous to the crew. Some of these chemicals range from mild irritants, such as the acid that can leak out of a damaged battery, to materials that can cripple or kill a crew member, such as the ammonia used for cooling. Except in the case of ammonia breaching the IFHX (see Chapter 11), there is no automatic annunciation of a toxic spill. The crew will detect it either from sight or from smell, and then annunciate the spill via the caution and warning panel. As was the case for fire, the IMV system is isolated to prevent the chemical from being dispersed throughout the ISS. Cleanup response to a toxic spill depends on what was spilled. All hazardous materials—i.e., HAZMATs—are logged into a database that lists the toxicity of every chemical used on the space station. Some are benign, but others can be extremely deadly. The flight control team and crew look at the database to determine the toxicity of the spill and the appropriate response. Basic response supplies are found in the Crew Contamination Protection Kit (CCPK). Mild spills can be cleaned up with wipes and silver shield gloves, which prevent absorption into the skin. Dirty wipes and towels are put in multiple plastic bags and carefully sealed to contain the material. In a bad spill, the crew members will don a respirator (Figure 12) and use the CMS to determine the air quality. For a really bad spill, the module might have to be closed off.