NASA seeks to ensure the health, safety, and functional abilities of astronauts and to prevent the exposure of astronauts to toxic levels of spacecraft contaminants. Consequently, exposure limits need to be established for continuous exposure of astronauts too spacecraft contaminants for up to 180 days (for normal space-station operations) and for short-term (1-24 hr) emergency exposures to high levels of contaminants. The SMAC reports are intended for use by engineers.