What is a blower door test ?

 

A blower door is a powerful fan that mounts into a frame that is placed in the opening of an exterior door. The fan pulls air out or pushes air into the building. It will either pressurize the building or depressurize the building. Air will be pulled through or pushed out any  unsealed penetrations in the building. The test determines the air infiltration rate of tightness of the building.