The Air Emissions Guide to USAF Transitory Sources (Transitory Source Guide) provides guidance for estimating emissions for transitory sources of pollutant emissions found at USAF installations.
Transitory sources of emissions are those that are non-routine and/or seasonal sources (which may be stationary, mobile, or neither) that are short-term in nature. The sources included in this guide
include bulk storage tank cleaning, seasonal equipment, fuel spills, hot mix asphalt plants, prescribed burns, wildfires, construction, site restoration/remediation, and land use changes.
Transitory sources have historically often been erroneously included in stationary or mobile source air emission inventories, though these sources should only be accounted for in evaluating potential air quality
impacts of proposed actions under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA); National Environmental Policy Act (NEPA); General Conformity; etc..
The pollutants addressed within this guide include criteria pollutants, Hazardous Air Pollutants (HAPs), Volatile Organic Compounds (VOCs), and greenhouse gases (GHGs).
The June 2021 guide supersedes all prior versions of the Mobile Source Guide; older versions are considered obsolete.