DC fire-safety design, commissioning & Li-ion checklist
The site-side companion to the fire calculator and fire-safety pillar: clean-agent design bands, the Li-ion battery-room requirements that NFPA 855 now mandates, the numeric commissioning procedure, PM cadences, a symptom→cause→action table, and a printable service-record form. Figures tagged STANDARD are from code; TYPICAL are common engineering practice — confirm against the AHJ, the equipment listing and a fire-protection engineer.
Acceptance bands for a gaseous clean-agent system in an IT/data hall (NFPA 2001). Agent quantity is set by W = (V/s)·(C/(100−C)) for halocarbons — compute it on the calculator.
Parameter
Novec 1230
FM-200
IG-541
Source
Class-A design concentration
~4.7%
~7.0%
~37.5%
NFPA 2001
Min. extinguishing concentration
3.5%
5.8%
34.2%
NFPA 2001
NOAEL (occupant safety ceiling)
10%
9.0%
43%
NFPA 2001
LOAEL
>10%
10.5%
52%
NFPA 2001
Discharge time
≤ 10 s (halocarbon)
≤ 60 s (inert)
NFPA 2001
Concentration hold (retention)
≥ 10 min (verified by door-fan test)
NFPA 2001
100-yr GWP
1
3,220
0
IPCC AR6
Atmospheric lifetime
~5 days
~36 yr
n/a
IPCC
Occupant rule. In a normally-occupied space the design concentration must stay at or below the agent NOAEL — FM-200's 9% NOAEL leaves little headroom above its ~7% design, while Novec 1230 and inert gases are comfortable. The calculator flags a NOAEL exceedance as a hazard.
02 Detection & alarm
Item
Requirement / band
Source
Very-early-warning (aspirating / VESDA)
Pre-alarm sensitivity ~0.005–0.05%/m obscuration; sampling network per design
NFPA 72
Spot smoke detector spacing
~9.1 m on-centre (≈84 m² per detector), reduced near airflow
NFPA 72
Cross-zoned release logic
Two independent detectors/zones must alarm before agent discharges
NFPA 72 / 2001
Pre-discharge warning + abort
Audible/visual alarm + time delay (typ. 30 s) and abort station
NFPA 2001
HVAC / damper interlock
Shut down air handlers + close dampers on confirmed alarm (room integrity)
TYPICAL
EPO (emergency power off)
Guarded two-stage station; coordinates with suppression release
NFPA 70 / 75
03 Lithium-ion battery-room fire safety
The modern gap. A Li-ion UPS/BBU pack in thermal runaway vents flammable gas (H₂/CO) whose volume vastly exceeds any room's flammable limit — so detection + ventilation lead, suppression follows. NFPA 855 + UL 9540A govern.
Why off-gas detection comes first. A 1,333 kWh NMC pack can release on the order of 5,000 m³ of vent gas and ~12 GJ of heat in full runaway (run it on the calculator). No practical clean-agent or sprinkler system "puts out" a propagating cell-to-cell runaway — the strategy is detect the off-gas early, ventilate/exhaust, isolate (BMS shutdown), and contain (compartmentation) to stop propagation, with suppression for any associated ordinary-combustible fire.
Requirement
Band / action
Source
Off-gas / combustible-gas detection
H₂ + CO sensors; alarm at ≤ 25% LFL (H₂ LFL 4% vol)
NFPA 855
Thermal-runaway onset (alarm before flame)
NMC ~150 °C · LFP ~166.8 °C · cell ΔT / dT/dt trending in BMS
UL 9540A / IEC 62619
Ventilation / explosion control
Mechanical exhaust sized to keep vent gas < 25% LFL; deflagration venting per NFPA 68/69 where required
NFPA 855
Unit spacing & fire-rated separation
Spacing per UL 9540A test results; rated walls to limit propagation
BMS isolates pack on cell fault; sequence vs agent discharge defined
NFPA 855 / 72
Suppression role
Clean agent / water mist for associated Class-A fire; NOT relied on to stop TR propagation
TYPICAL
04 Commissioning — numeric procedure
Room integrity (door-fan) test. Measure equivalent leakage area; confirm the agent concentration is retained for the required hold time (≥10 min). Seal penetrations and re-test until pass. NFPA 2001
Agent quantity & cylinder charge. Verify charged weight/pressure vs the design (W = (V/s)·(C/(100−C))); record cylinder serials, fill weight and superpressurization. NFPA 2001
Discharge test (where required). Confirm full discharge ≤ 10 s (halocarbon) / ≤ 60 s (inert) and measured concentration reaches design. NFPA 2001
Detection cross-zone verification. Prove no single detector releases agent; confirm pre-discharge delay + abort + manual release. NFPA 72
HVAC/damper + EPO interlocks. On confirmed alarm: air handlers stop, dampers close, EPO sequence verified. NFPA 70/75
Li-ion off-gas detection commissioning. Calibrate H₂/CO sensors; verify alarm at ≤25% LFL and exhaust/ventilation start; confirm BMS-shutdown sequence. NFPA 855
Integrated systems test (IST). End-to-end: detection → alarm → HVAC → EPO → release → BMS, all together. TYPICAL
05 Installation checklist
Enclosure sealed (cable penetrations, floor/ceiling voids, dampers) for room integrity
Cylinders mounted, restrained, labelled; discharge nozzles positioned per drawings
Detectors (aspirating + spot) installed, addressed, cross-zoned to the panel