Photos Source: Summerhill

• A blower door is used to determine how air tight the home is
• All windows and exterior doors must be closed during the test
• All interior doors must remain open during the test
• The blower door measures the pressure difference between the exterior and interior of the home
• The test is performed at 50 pascals which simulates a 33 km/hr wind blowing on the house equally from all directions ( Reference: ERS Technical Procedures V.15.3 Sec.7.6)
• This forces air into or out of the home through leakage areas depending on the type of test performed
• Leakage areas can be found by walking around the home while the fan is on and
  
  • Feeling with the back of the hand
  • Using a smoke pencil or other smoke emitter
  • Looking for movement caused by moving air
• The blower door can also perform a test, known as the depressurization test, which can determine if spill susceptible appliances may back draft.