Definition of Pascals

A Pascal is a very minute metric unit of pressure measurement. Most folks know what a PSI is (pounds per square inch) is. A racing road bicycle may have over 100 PSI, and a car tire may have about 35 PSI. A dirt bike (motorcycle) tire may have 15 PSI. A beach ball may have only several PSI to give it all that bounce.

If PSI can be compared to a jumbo jet, the Inches of Water Column would be considered a single engine airplane. There are about 28 of water column (WC) in one PSI. Many of us recall from our science class days that one PSI will push a column of water 2.304 upwards, which is right around 28. Many HVAC diagnostics are measured in WC, and in 1/10ths of WC.

If WC is a single engine air plane, the Pascals are like model air planes. There are 250 Pascals (Pa) in an inch of water column (WC). A typical blower door test in a home would pull a negative pressure of 25 Pa, or 1/10th of one inch of water column. This is only measured with extremely sensitive diagnostic equipment.