Short term radon testing, which is the type of testing performed during real estate transactions requires closed-house conditions. This means simply that all windows must be closed, doors must be closed except for normal entry and exit, and not operating fans or other appliances that bring outside air into the home (exceptions include radon reduction fans and small exhaust fans operating for short periods of time).

Before Testing: 

• Begin closed-house conditions at least 12 hours prior to start of radon test