3. Identify potential sources of strong blast within the area covered by the flammable cloud.
Potential sources of strong blast include congested areas and buildings, such as process
equipment in chemical plants or refineries, stacks of crates or pallets, and pipe racks;
spaces between extended parallel planes (for example, those beneath closely parked cars
in parking lots; and open buildings, for instance, multistory parking garages); spaces
within tubelike structures (for example, tunnels, bridges, corridors, sewage systems, culverts);
and an intensely turbulent fuel-air mixture in a jet resulting from release at high
pressure. The remaining fuel-air mixture in the flammable cloud is assumed to produce
a blast of minor strength.