Fire protection
Size the agent, count the detectors and walk the release sequence for one protected room.
Container size is the listed system’s — the defaults are placeholders to replace. Volume is the gross enclosure, including raised floor and ceiling voids if they are flooded. Subtract only permanent, impermeable solids.
Data halls commonly run 30–60+ air changes per hour; that, not the 9.1 m nominal spacing, sets the detector count.
A typical cross-zoned sequence. The pre-discharge delay, which outputs are tripped at which stage, and whether an abort switch is fitted are site programming approved by the AHJ — not fixed by NFPA 2001.
| Sprinkler system | Pipe normally holds | Water enters the pipe when | Fit for IT space |
|---|---|---|---|
| Wet pipe | Water | Always there | Simple and reliable; a damaged head leaks at once |
| Dry pipe | Pressurised air / N₂ | A head opens | For freezing spaces; slower water delivery |
| Pre-action, single interlock | Air (supervised) | Detection operates | Common in data halls |
| Pre-action, double interlock | Air (supervised) | Detection operates and a head opens | Lowest accidental-discharge risk |
| Standard | Covers |
|---|---|
| NFPA 75 | Fire protection of IT equipment: construction, detection, suppression, and the IT room disconnecting means |
| NFPA 76 | Fire protection of telecommunications facilities |
| NFPA 72 | Fire alarm and signalling: detector spacing, aspirating systems, notification |
| NFPA 2001 | Clean-agent systems: quantity, discharge time, retention (hold) time, safety |
| NFPA 13 | Sprinkler installation, including pre-action systems |
| NFPA 70 Art. 645 | Information technology equipment rooms: disconnecting means, wiring under raised floors |
| NFPA 855 | Stationary energy storage systems (lithium-ion UPS batteries) |
Retention. A clean-agent enclosure must hold the agent long enough for the fire to stay out — commonly verified as at least 85 % of the design concentration at the top of the protected contents after a 10-minute hold, proved with a door-fan integrity test.