Enclosure Integrity Test Application:
Enclosures protected by gaseous fire suppression systems must be airtight in order to maintain concentration and effectively prevent re-ignition. NFPA 2001 Annex C and ISO 14520 Annex E both require a Door Fan (blower door) Test to prove that the protected enclosure is tight enough to maintain sufficient concentration.
Test results can also be used to predict how much pressure will develop in an enclosure when the gas 
discharges, to ensure that this pressure will not knock down any walls or blow out any windows.
A typical Blower Door system is comprised of four main parts:
1. A Door Panel, which temporarily seals a typical doorway and provides a hole to mount a fan. 2. A calibrated fan, capable of creating a measurable flow of air.
3. A two-channel differential pressure gauge that can also calculate flow for a particular fan.
4. A fan speed controller to change the air flow through the fan (can be provided by the gauge).
The specially designed calibrated fan is temporarily mounted in a doorway using the Door Panel. The fan is used to blow air into or out of a room, or building, to measure the air leakage of the protected enclosure. The gauge measures the pressure across the calibrated fan and calculates the flow or other values of interest (such as equivalent leakage area). The Blower Door Systems measure the amount of air leakage by establishing a pressure difference between the inside and the outside of an enclosure. The pressure difference forces air to leak through all of the holes in the exterior envelope of the enclosure. The amount of air flow that is required to maintain a constant pressure difference is equal to the amount of air that is leaking from the enclosure.
A specially designed gauge can thus be used to measure the pressure difference and calculate the amount of air flowing through the calibrated fan, which can then be used to determine the total size of all those leaks. Once the leakage is quantified, the results are entered into FanTestic Integrity software which will calculate how long an acceptable concentration will be maintained (called the hold time) based on formulas in either the NFPA or the ISO standard.
The software also makes the calculations to predict how much pressure will develop in an enclosure when the gas discharges, and the required size of additional venting to reduce the overpressure to an acceptable level.
NB: The ability for the gaseous agent to be retained in the protected room for an extended period of time is critical to the performance of any total flooding clean agent fire extinguishing system. NFPA 2001, Standard on Clean Agent Fire Extinguishing Systems, requires that a minimum concentration of 85% of the adjusted minimum design concentration be held at the highest level of combustibles for a minimum period of 10 minutes.