A blower door, blower door*, or infiltrometry test is a machine used to measure the airtightness of buildings. It can also be used to measure current between built areas, to test the tightness of air conductors and to help physically locate air escape sites in the building envelope.[1]​.

There are three primary components in a blower door: (1) a calibrated variable-speed fan, capable of inducing a range of airflows sufficient to pressurize and depressurize a variety of building sizes, (2) a pressure measuring instrument, called a manometer, to simultaneously measure the pressure differential induced around the face of the fan and across the building envelope, as a result of the blower airflow, and (3) a mounting system, used to mount the fan in an opening. of the building, such as a door or window.

Air tightness testing is normally intended for residential settlements. Likewise, it is becoming increasingly common in commercial settlements. The United States General Services Administration (GSA) requires testing of new federal government buildings.[2]​.

A variety of blower door airtightness metrics can be produced using the combination of building-to-outdoor pressure and blower airflow measurements. These metrics differ in their methods of measurement, calculation, and uses. Blower door testing is used by construction researchers, HVAC professionals, crews, home performance contractors, home energy auditors, and other professionals dedicated to evaluating the construction quality of the building envelope, locating air escape routes, evaluating how much ventilation goes through the exhaust air, evaluating the energy losses that result from the exhaust air, determining if the building is too tight or too loose, determining if the building needs ventilation "Ventilation (architecture)") and evaluate compliance with construction performance standards.[3]​.