NICET Special Hazards III flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

NOAEL

No Observed Adverse Effect Level: the highest agent concentration at which no adverse physiological effect was observed in testing. Clean agent designs for occupied spaces must not exceed the NOAEL.

LOAEL

Lowest Observed Adverse Effect Level: the lowest concentration at which an adverse effect was observed. LOAEL is used to set egress and exposure limits for short-duration occupant exposure.

Design concentration

The agent concentration selected for a total-flooding system, at or above the minimum extinguishing concentration for the hazard class and, for Class C, at or below the NOAEL.

Hold time

The period during which the design concentration is maintained in the protected enclosure after discharge, allowing occupant egress and preventing re-ignition; typically at least 10 minutes.

FM-200 NOAEL

HFC-227ea (FM-200) has a NOAEL of 9.0 percent by volume. Class C designs must not exceed 9.0 percent, and occupied-space exposure must stay below that level.

Inergen NOAEL

IG-541 (Inergen) has a NOAEL of 43 percent by volume. Class C designs must not exceed 43 percent, and Class B designs commonly reach that limit.

Novec 1230 NOAEL

FK-5-1-12 (Novec 1230) has a NOAEL of 10 percent by volume, well above typical Class A and Class B design concentrations of roughly 4.2 to 5.85 percent.

CO2 total-flooding restriction

Carbon dioxide total-flooding systems are prohibited in occupied spaces because the design concentration is lethal. They are permitted only in unoccupied areas with lockout and pre-discharge alarm.

Pre-discharge alarm

A distinctive alarm required before clean agent discharge in occupied areas, paired with a time delay (commonly 30 seconds) to allow occupants to egress safely.

Abort station

A manual device that stops the pre-discharge timer and prevents agent release, typically located at the egress door and permitted only where the hazard does not require immediate discharge.

Halocarbon agent formula

NFPA 2001 agent quantity: W = (V/S) x (C/(100-C)), where W is mass, V is enclosure volume, S is specific vapor volume at design temperature, and C is design concentration.

Inert gas agent formula

Agent mass = (enclosure volume x design concentration x gas density) / (1 - design concentration), with altitude correction applied to the enclosure volume for inert-gas systems.

Class C hazard

An energized electrical or electronic hazard. Clean agent design concentration for Class C must not exceed the NOAEL, and the agent must be non-conductive.

Class B hazard

A flammable liquid or gas hazard. Clean agent design concentrations for Class B are typically higher than Class A and are set by the minimum extinguishing concentration plus a safety factor.

Class A hazard

An ordinary combustible hazard such as paper or wood. Clean agent design concentrations for Class A are typically the lowest of the three classes, commonly 6.25 to 7.0 percent for FM-200.

Total-flooding system

A system that discharges agent into an enclosure to achieve and maintain a design concentration throughout the protected volume, requiring a sealed enclosure and pressure relief venting.

Pressure relief vent

A vent sized to relieve the overpressure created by agent discharge in a sealed enclosure, preventing structural damage while maintaining the design concentration hold time.

Enclosure integrity test

A door-fan or equivalent test that measures enclosure leakage to confirm the space can hold the design concentration for the required hold time before system acceptance.

Clean agent

A non-conductive, electrically non-conducting, volatile extinguishing agent that leaves no residue, such as FM-200, Novec 1230, or Inergen, used for total-flooding applications.

Halocarbon agent

An agent containing carbon and halogen atoms, such as HFC-227ea or FK-5-1-12, that extinguishes primarily by absorbing heat and interrupting the combustion chain.

Inert gas agent

An agent such as IG-541, IG-55, or IG-01 that extinguishes by reducing oxygen concentration below the level supporting combustion while remaining breathable at design concentration.

Specific vapor volume (S)

The volume occupied by a unit mass of agent vapor at the design temperature, used in the NFPA 2001 halocarbon agent quantity formula to convert enclosure volume to agent mass.

Discharge nozzle

A device that distributes agent uniformly throughout the protected enclosure; nozzle type, spacing, and elevation are selected from the manufacturer's listed design manual.

Piping hydrostatic test

A pressure test of the agent piping at a pressure above the design working pressure, performed before acceptance to confirm the piping and fittings will contain the discharge.

Detection cross-zoning

A design where two independent detectors must both alarm before agent discharge, reducing false discharges; the arrangement is defined by the system design and listing.

Clean agent cylinder storage

Agent cylinders must be stored within the listed temperature range, secured against movement, and located where ambient temperature does not cause overpressurization or under-discharge.

Weighing agent cylinders

The primary method to verify halocarbon agent quantity in the field: compare cylinder weight to the stamped fill weight, since pressure gauges do not reliably indicate agent loss.

NFPA 2001

The standard for clean agent fire extinguishing systems, covering design concentration, agent quantity, hold time, enclosure integrity, and occupant safety requirements.

NFPA 12

The standard for carbon dioxide extinguishing systems, covering total-flooding, local application, and CO2 restrictions for occupied spaces.

NFPA 12A

The standard for halon 1301 fire extinguishing systems, covering design, installation, and the phase-out and recycling requirements for halon agents.

NFPA 750

The standard for water mist fire protection systems, covering design, installation, and acceptance testing for water mist systems used on special hazards.

NFPA 2010

The standard for fixed aerosol extinguishing systems, covering design, installation, and the limitations of condensed and dispersed aerosol agents for special hazards.