Public Health Information Paper (PHIP) 39-09-1118 presents a standard set of inhalation rates linked to exposure timeframes that can be used when developing military exposure guidelines (MEGs). The methodology presented provides for the consideration of a variable inhalation rate when developing exposure guidelines where the actual exposure rate is unknown. It recommends higher inhalation rates for shorter durations be used by default, but provides instructions for adjusting inhalation rates for specific assessments where more information about activity level or inhalation rate is known.