Preliminary Determination:

Porous HVAC System Surface: Any surface of the
HVAC system in contact with the air stream that is
capable of penetration by either water or air. Examples
include fiber glass duct liner, fiber glass duct board,
wood, and concrete.
Preliminary Determination: A conclusion drawn from the
collection, analysis and summary of information obtained
during an initial inspection and evaluation to identify
areas of moisture intrusion and actual or potential mold
growth (IICRC S520).
Pressure Drop: (1) Loss in pressure, as from one end of
a refrigerant line to the other, from friction, static, heat,
etc.; (2) Difference in pressure between two points in a
flow system, usually caused by frictional resistance to
fluid flow in a conduit, filter or other flow system (See