Although these process-oriented emissions control measures are useful, emissions
capture equipment and add-on emissions control equipment are also necessary in new asphalt
roofing production facilities that are subject to the NSPS. The capture of potential POM
emissions from asphalt blowing stills, asphalt storage tanks, asphalt tank truck unloading, and the
coater-mixer can be and is being achieved in the industry by the use of enclosure systems around
the emissions operations. The enclosures are maintained under negative pressure, and the
contained emissions are ducted to control devices (U.S. EPA, 1980). Potential emissions from
the saturator, wet looper, and coater are generally collected by a single enclosure, by a canopy
type hood, or by an enclosure/hood combination. Typically applied controls for POM emission
sources in asphalt roofing plants are summarized in Table 4.6-1.