NICET Special Hazards II cheat sheet

NFPA 2001 governs clean agent total-flooding systems; NFPA 750 governs water mist; NFPA 2010 governs aerosol extinguishing; NFPA 17 and 17A govern dry chemical and wet chemical systems; NFPA 15 governs water spray fixed systems.

Clean agent design concentration must equal or exceed the class-specific extinguishing concentration with a safety factor added: NFPA 2001 requires the greater of the listed minimum design concentration or the extinguishing concentration multiplied by 1.2 for Class B heptane cup burner values.

Class A clean agent designs use the wood crib or Class A fuel extinguishing concentration plus the required safety margin; Class C hazards apply only where electrical equipment is de-energized on discharge unless the agent is rated non-conductive.

Total flooding requires enclosure integrity: NFPA 2001 hold time is typically 10 minutes for occupied spaces, and a door fan test verifies agent retention against the design concentration at the hold-time endpoint.

Agent quantity for total flooding is computed from the design concentration using the ideal gas relationship W = V * C / (100 - C) * (agent density factor), with V corrected for any permanent openings and solid obstructions.

Halocarbon and inert gas agents have different design equations: inert gases (IG-541, IG-100, IG-55) use the volume-displacement form with a k-factor, while halocarbons use the vapor density form; never interchange the two.

Water mist systems are classified by application (NFPA 750): residential, light hazard, ordinary hazard occupancies, and special applications; each has distinct discharge density and nozzle spacing criteria.

Wet chemical systems (NFPA 17A) are for kitchen cooking equipment and discharge a potassium-based agent that saponifies animal and vegetable fats; dry chemical systems (NFPA 17) serve flammable liquid and gas hazards.

Detection and control must be listed for the application: cross-zoning of detectors is required for clean agent total flooding to reduce false discharge, and manual release plus abort switch must be provided at the egress door.

Cross-zoned detection requires two independent detectors or zones to alarm before discharge; a single detector alarm typically activates only a pre-discharge alarm and annunciation.

The pre-discharge time delay must allow occupant egress; NFPA 2001 requires a minimum 30-second delay for occupied spaces unless the authority having jurisdiction approves otherwise, and the delay is adjustable but not eliminable.

Abort switches must be located at the egress door, must be a dedicated manual device, and must be capable of being reset; they are not permitted to substitute for a manual pull station.

Manual release stations are required at each egress door from the protected space and must be clearly identified; actuation must cause immediate discharge without the time delay.

Predischarge and discharge alarms must be distinct: the predischarge alarm is a continuous or pulsed signal during the delay, and the discharge alarm sounds on agent release with a distinct audible/visual pattern.

Detection spacing follows the listed device: spot-type smoke detectors per NFPA 72 spacing (30 ft nominal on smooth ceilings, reduced for joists and beams), and linear beam detectors require specific spacing per listing.

Supervisory and trouble signals must annunciate distinctly from alarm signals; a valve supervisory switch on the agent container is a supervisory, not alarm, condition.

Releasing circuits must be supervised and arranged so a single fault does not prevent discharge; NFPA 72 requires Class A or equivalent supervision for the releasing circuit in most designs.

The control panel must be listed for releasing service (NFPA 72 releasing panel requirements), and the sequence of operation must be documented and tested at acceptance.

Piping for clean agent systems must be designed per the manufacturer's listed calculation method; the hydraulic or flow calculation must be submitted with the design and verified against nozzle pressure limits.

Nozzle discharge orifices must be sized per the listed design and installed at the height and spacing shown; nozzle orientation and deflector distance to the ceiling are manufacturer-specific and must be maintained.

Pipe and fittings must be the materials listed for the agent (e.g., Schedule 40 black steel or specific listed materials); galvanized or copper may be prohibited for some halocarbon agents by the listing.

Hydrostatic testing of agent containers and piping is required at intervals; containers must be weighed or have their pressure checked at the interval specified in the applicable standard (typically semiannual inspection, with container weight verification).

Acceptance testing requires a door fan enclosure integrity test to confirm the hold time, plus a full-flow test or a puff test per the manufacturer's listed acceptance procedure.

The flow test must verify that agent quantity, discharge time, and nozzle pressures match the design; discharge time for clean agents is typically 10 seconds or less for halocarbons and 60 seconds or less for inert gases.

Pressure relief and venting must be provided for enclosures where the agent can overpressurize the space; NFPA 2001 requires pressure relief venting sized to the enclosure and agent.

Pipe hangers and supports must be listed and spaced per the manufacturer's requirements and NFPA 13/NFPA 15 support spacing where applicable; supports must accommodate thermal expansion.

Post-discharge recharging requires replacing the agent, re-verifying container weight and pressure, and inspecting nozzles and piping for obstruction before returning the system to service.

NFPA 25 does not cover clean agent or special hazards systems; inspection, testing, and maintenance of clean agent systems follows NFPA 2001 Chapter 7 and manufacturer instructions, with annual inspection and testing of the system.

Container weight or pressure check is required at each inspection interval; a container that has lost more than 5 percent of its weight or has a pressure outside the listed range must be recharged or replaced.

The 5-year and 12-year intervals apply to certain containers and hoses: NFPA 2001 requires hydrostatic testing of containers at 5-year intervals for some agents and hose conductivity/retest per manufacturer, so verify the specific agent's listed interval.

Inspection records must document agent quantity, container pressure, condition of nozzles and piping, detection devices, alarms, and the releasing panel sequence test.

Impairment procedures require notifying the authority having jurisdiction, the owner, and the alarm company before taking a system out of service, and posting a tag at the panel and container.

A system impairment must be tracked with a permit or tag system; the impairment coordinator is responsible for restoring the system and documenting the restoration.

Functional testing of the releasing panel must include simulated detector activation, verification of the time delay, abort function, and manual release without actually discharging agent.

Detection devices must be cleaned and recalibrated or replaced per the manufacturer's schedule; smoke detectors in dirty environments require more frequent cleaning than the standard annual interval.

After any discharge, whether accidental or actual, the system must be fully recharged, the cause investigated, and the event reported to the owner and AHJ before the system is returned to service.