A Room Integrity Fan Test, also known as a Door Fan Test, is simply a way to measure the leakage of an enclosure. A large fan is temporarily installed in the doorway of the room to be tested, with the fan blowing into the room (pressurizing the room). The fan speed is adjusted to obtain flow pressure equivalent to the pressure exerted during a fire suppression system discharge. The fan is then reversed on the door to draw air from the room (depressurizing the room). The airflow and pressure readings obtained are entered into a computer program designed to calculate the equivalent leakage area (ELA) for the room. When a room has a suspended (drop) ceiling, then the below ceiling leakage area (BCLA) is calculated as one-half the total ELA and is used in the calculations for retention time. Given that most gaseous chemical agents used for fire suppression are heavier than air, the agent will begin to leak out of any lower level penetrations left unsealed.