Room Integrity, Door Fan Testing and Pressure Relief

Room integrity is a protected room’s ability to hold the gas suppression agent discharged into it at design concentration for the hold time required by the applicable standard. Leakage paths — gaps under doors, cable and pipe penetrations, ceiling voids, ventilation dampers — can let that gas escape before hold time is complete. A room integrity test — commonly called a door fan test on site — pressurizes and depressurizes the room with a calibrated fan to measure total equivalent leakage area, and from that figure calculates whether the expected retention time meets the minimum required by the standard, without ever having to perform a real gas discharge.

Why Room Integrity Matters So Much

The core assumption behind gas suppression design is that the gas delivered to the protected space will remain at design concentration for a defined period — the hold time, calculated at the design stage for the specific agent used (see “Design Concentration and Hold Time”). But no room is perfectly airtight; gaps under doors, cable ducts, outlet boxes, ceiling voids, and raised-floor gaps all leak gas over time. Once leakage exceeds a certain threshold, room concentration drops below the safe extinguishing threshold before hold time is complete, and smoldering or reheated surfaces can reignite the fire. This holds regardless of agent family: it applies to inert gas systems just as much as to FM-200 or FK-5-1-12 (Novec 1230) clean-agent systems — without adequate sealing, the design concentration simply cannot be held as calculated. Room integrity is therefore just as integral a part of system design as cylinder and nozzle sizing.

How a Room Integrity (Door Fan) Test Works

The test uses a calibrated fan and pressure-measurement equipment mounted in the room’s doorway. The fan first pressurizes the room relative to the outside, then depressurizes it; airflow measured at several pressure steps in both directions is used to calculate the room’s total equivalent leakage area (ELA). That leakage-area value, together with parameters such as protected volume, ceiling height, design concentration, and gas type, is entered into specialized software to simulate the concentration decay curve that a real discharge would produce, predicting whether the room will meet the hold time defined by the relevant standard. This test is carried out on site as part of GYS’s Room Integrity (Door Fan) Testing service.

Verification Without a Real Gas Discharge

The most valuable practical benefit of this method is that it can verify a room’s performance without actually discharging expensive, refill-requiring gas — even before the system is commissioned. If the calculated retention time comes up short, a smoke generator or leak-detection equipment is used to pinpoint exactly where the leaks are, and the issue is corrected with fixes such as door-bottom seals, sealing cable penetrations, or adding dampers, after which the test is repeated. This is a far more practical verification route, both in cost and site feasibility, than a live discharge test.

When Should Testing Be Done?

A door fan test is a mandatory step at initial commissioning; it should also be repeated after any change that could affect the room’s structural integrity (a new cable or pipe penetration, a door replacement, ceiling or floor work), and at intervals as part of the periodic maintenance program. In server rooms with heavy cable traffic especially, new penetrations opened over time can silently compromise sealing, which makes periodic retesting critical.

Pressure Relief: The Other Side of Room Integrity

A gas discharge causes a pressure change in the protected room that lasts a fraction of a second. Inert gases (IG-541, IG-55) always create positive, outward pressure; chemical agents such as FM-200 and FK-5-1-12 can create positive pressure, negative pressure or both, depending on the agent and humidity. According to an assessment published by SFPE, this peak pressure is typically in the 240-1,200 Pa range; a securely fastened double-sided partition can take about 500 Pa, while a suspended ceiling can take only about 50 Pa.

This creates a conflict: the tighter the room, the longer it holds the agent, but the higher the peak discharge pressure. NFPA 2001 requires an estimate of the maximum positive and negative pressure during discharge, and venting where these pressures threaten the structural strength of the enclosure. The need for a pressure relief vent is therefore assessed from the leakage area measured by the door fan test together with the room construction.

Points we watch in practice:

• The vent is placed as high as possible so that lighter air, not the denser agent, is released.
• The opening pressure is chosen so the vent stays closed under normal HVAC pressures (about 50 Pa) but opens before the room is damaged (not above about 100 Pa).
• Chemical agents may need venting in both directions; the free area of dual-acting vents is tested in each direction.
• After installation the closed vent’s leakage is measured, and the annual maintenance checks that it opens and that the vent path is not blocked.

Vent size follows the agent and the system manufacturer’s calculation method. That calculation is part of design engineering, and vent installation and sealing work are part of our room integrity construction service.

Common Points of Leakage

The most frequently encountered leakage sources in the field include gaps under doors (particularly doors without automatic closers or with worn seals), missing or damaged seals around cable and pipe penetrations under raised floors, ceiling panels that don’t sit fully flush, and ventilation dampers that fail to close automatically during gas discharge. Reviewing these points with the architectural and mechanical teams at the design stage reduces the remediation work a door fan test is likely to uncover later. The test report should record not just the result value but also the location of any leaks found, making it easier to check the same points again during future periodic testing.

Why Consider Room Integrity at the Design Stage?

Room integrity isn’t a detail to discover after commissioning — it’s a design input that belongs in the project from the start. While cylinder count, nozzle layout, and design concentration are being calculated (see “Design Concentration and Hold Time”), how airtight the room can realistically be built also needs to be part of the same process; otherwise site conditions can invalidate the calculation on paper. This is why the architectural and mechanical drawings’ door, wall, ceiling, and cable/pipe penetration details should be cross-checked against the gas suppression design while the room is still under construction — a fix made at the design stage is always cheaper and easier than one made afterward.

Why It’s Critical in Data Centers, Server Rooms, and Electrical/Electronic Rooms

Room integrity plays a decisive role especially in spaces like data centers and server rooms, which combine high-value, water-sensitive equipment with sometimes-occupied areas: these rooms typically carry a large number of cable ducts, raised-floor voids, and ceiling penetrations, which raises the leakage risk. The same logic applies to electrical/electronic panel and distribution rooms, down to cabinet-scale protection such as panel/cabinet suppression: however small the protected volume, design concentration cannot be held for the calculated duration without adequate sealing. That’s why room integrity testing is treated as a standard commissioning step in these critical spaces, on par with the system’s other components.

To apply this guide to your project, see our gas fire suppression services and every system option on our home page, or contact us through the quote form.

Last updated: 26 October 2026