This paper presents the methods and philosophies for hazardous atmosphere prevention, response, and recovery onboard the International Space Station (ISS). The paper discusses the various levels of hazardous atmosphere and then design controls used for both ISS systems and payloads. Subsequently, a brief mention is made of the training and procedures the crew will follow. The body of the paper then deals with the philosophies and methods for spill control, monitoring and cleanup. It begins by discussing annunciation methods and continues by listing basic response ground rules and assumptions. Finally, more specific spill response philosophies are discussed under the headings of Isolation, Assessment, Cleanup, and Report.