PE Fire Protection flashcards

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

T-squared fire growth model

Heat release rate grows as Q = αt², where α is 0.00293 kW/s² (slow), 0.0117 (medium), 0.0469 (fast), or 0.1876 (ultrafast).

Flashover indicators

Flashover is assumed near an upper-layer temperature of 600 °C, a floor-level radiant flux of about 20 kW/m², or sustained flames emerging from openings.

Standard fire curve equation

ASTM E119 and ISO 834 use T = 20 + 345 log10(8t + 1), where T is furnace temperature in °C and t is elapsed time in minutes.

Ventilation-limited burning rate

Kawagoe correlation ṁ = 0.5 A√H kg/s, with A the total opening area in m² and H the weighted opening height in meters.

Heskestad flame height correlation

L = 0.235 Q^(2/5) − 1.02 D gives mean flame height in meters from heat release rate Q in kW and fire diameter D in meters.

Radiant flux injury thresholds

About 2.5 kW/m² is the skin pain threshold, 10 kW/m² produces severe burns within seconds, and 20 kW/m² is associated with flashover conditions.

Fire risk assessment equation

Risk equals probability multiplied by consequence; hazard identification, frequency analysis, consequence analysis, and risk evaluation against tolerability criteria form the assessment process.

NFPA 101 scope

NFPA 101, the Life Safety Code, sets minimum requirements for protecting occupants from fire and similar emergencies, covering means of egress, fire protection features, and operating features.

IBC occupancy groups

Occupancies are classified as A, B, E, F, H, I, M, R, S, or U; the H group denotes high hazard and generally carries the strictest construction and protection requirements.

Assembly occupant load factor

IBC Table 1004.5 assigns 15 ft² net per occupant for unconcentrated assembly and 7 ft² net for concentrated assembly without fixed seats.

NFPA 13 design scope

NFPA 13 covers the design and installation of automatic sprinkler systems, including design density, sprinkler spacing, hydraulic calculations, and water supply requirements.

Role of the AHJ

The authority having jurisdiction enforces the adopted code edition and may approve alternative materials, methods, or equivalencies when equivalent fire safety is demonstrated and documented.

NFPA 25 scope

NFPA 25 establishes minimum inspection, testing, and maintenance frequencies for water-based fire protection systems, with intervals set by component type and system configuration.

Smoke detector spacing limits

On smooth ceilings NFPA 72 allows 30 ft (9.1 m) nominal spacing, with the first detector placed within 0.7 times that spacing, about 21 ft, of a sidewall.

Heat detector wall offset

Heat detectors are spaced to walls at half the listed spacing, while spacing must be reduced for ceiling heights above 10 ft per NFPA 72 reduction curves.

Public mode alarm audibility

Public mode requires 15 dBA above average ambient or 5 dBA above maximum ambient lasting over 60 s, at least 75 dBA at 10 ft, and no more than 110 dBA.

Sprinkler waterflow alarm timing

A waterflow alarm must actuate within 90 seconds of a sustained flow equal to that required to operate a sprinkler, unless the flow is below the retard threshold.

Duct smoke detector threshold

NFPA 90A requires duct smoke detectors where an air-handling unit exceeds 2,000 cfm and serves more than one story or more than 15,000 ft².

Ionization versus photoelectric detection

Ionization detectors respond faster to flaming fires producing small particles, while photoelectric detectors respond faster to smoldering fires producing larger smoke particles.

Class A versus Class B circuits

Class A initiating device and notification circuits continue to function with a single open or ground fault; Class B circuits lose that circuit segment and require two conductors.

Light hazard design density

NFPA 13 light hazard design commonly uses 0.10 gpm/ft² over 1,500 ft², applicable to offices, schools, and other occupancies with low combustible loading.

Ordinary hazard Group 2 density

Ordinary hazard Group 2 uses 0.20 gpm/ft² over 1,500 ft² as a standard density/area point for occupancies such as mercantile and parking garages.

Sprinkler discharge formula

Sprinkler flow follows Q = K√P, so a K = 5.6 sprinkler at 50 psi discharges roughly 39.6 gpm; doubling pressure raises flow by about 41 percent.

Fire pump performance points

NFPA 20 requires at least 150% of rated flow at not less than 65% of rated head, with churn pressure not exceeding 140% of rated pressure.

Dry pipe design area increase

Dry pipe and double-interlock preaction systems require the hydraulically calculated design area to be increased 30% above the wet system area for the same hazard.

Hazen-Williams friction loss

Friction loss p = 4.52 Q^1.85 / (C^1.85 d^4.87), with p in psi per foot, Q in gpm, d in inches, and C the pipe roughness coefficient.

Egress width per occupant

IBC requires 0.2 in. of capacity per occupant on level components and 0.15 in. on stairs, while NFPA 101 uses 0.2 in. and 0.3 in.

Travel distance limits

IBC Table 1017.2 limits travel distance to 200 ft in nonsprinklered and 250 ft in sprinklered business and mercantile occupancies, with lower limits for hazardous uses.

Dead-end corridor limits

Dead-end corridors are limited to 20 ft in nonsprinklered buildings and 50 ft where automatic sprinklers are provided, measured from where the single path begins.

Egress door clear dimensions

Egress doors must give at least 32 in. clear width and 80 in. clear height, and must swing in the direction of travel where the occupant load is 50 or more.

Stair pressurization differential

NFPA 92 stairwell pressurization typically maintains 0.05 to 0.10 in. w.c. across the door, with the opening force limited to 30 lbf.

Interior finish flame spread classes

ASTM E84 Class A spans flame spread 0 to 25, Class B spans 26 to 75, and Class C spans 76 to 200, with smoke-developed index limits also applying.