Duct leakage testing

A duct leakage tester is a diagnostic tool designed to measure the airtightness of forced air heating, ventilating and air-conditioning (HVAC) ductwork.

Ductwork that is outside the building envelope, such as in an unconditioned attic or crawlspace, should be pressurized so as to not bring in unwanted contaminants such as dust.

Duct tester airtightness measurements are presented in a number of different formats including but not limited to: CFM25 is defined as the air flow (in cubic feet per minute) needed to create a 25 Pascal pressure change in the ductwork.

Leakage area estimates are a useful way to visualize the equivalent cumulative size of all leaks or holes in the ductwork.

Commercial and industrial ductwork is often tested to standards developed by the Sheet Metal and Air Conditioning Contractors' National Association (SMACNA).

The next step requires measuring the pressure in the taped off duct system with respect to the building.

This method does not quantify duct leakage, but serves to identify locations of ductwork runs that are leaking to the outside.