The units are conventionally used for measurement of certain pressure differentials such as small pressure differences across an orifice, or in a pipeline or shaft,[1] or before and after a coil in an HVAC unit.
At that temperature and assuming the standard acceleration of gravity, 1 inAq is approximately 249.082 pascals (0.0361263 psi).
[3] In North America, air and other industrial gases are often measured in inches of water when at low pressure.
One usage is in the measurement of air ("wind") that supplies a pipe organ and is referred simply as inches.
It is also used in natural gas distribution for measuring utilization pressure (U.P., i.e. the residential point of use) which is typically between 6 and 7 inches WC or about 0.25 lbf/in2.