What are the fire classes?

Per NFPA 10-2022 and ISO 7165: A = ordinary combustibles (wood, paper, cloth); B = flammable liquids/gases; C = energised electrical; D = combustible metals; K = kitchen oils/fats. Each requires a different extinguishing agent.

Can a CO₂ extinguisher fight a wood fire?

Not effectively. CO₂ smothers liquid/electrical fires but doesn't cool the fuel — wood will re-ignite when the gas disperses. CO₂ is rated B and C only; use water or foam (Class A) for combustibles.

What mismatches are dangerous?

Water on energised electrical (Class C) — electrocution. Water on burning oils (Class K) — violent steam explosion. The tool flags any mismatch between extinguisher type and the fire class you've selected.

What muster time is acceptable?

Onshore industrial: 5–7 minutes to muster point. Offshore (lifeboats): under 7 minutes per IMO LSA Code. High-occupancy buildings: per NFPA 101-2024 the egress time depends on travel distance and exit width. The tool helps benchmark — it doesn't replace a written emergency response plan.

What flow capacity should I use for doors?

NFPA 101 commonly assumes ~1.3 persons per metre of effective door width per second at pinch points. Stairs reduce flow further (~0.8 p/m/s). Add safety margin for older or impaired occupants.

Does this match a drill?

The tool gives a theoretical lower bound. Actual drills typically take 1.5–2× the calculated time because of orientation, secondary-route choice, and head-counting at the muster point. Always validate with periodic drills, not just calculation.

What does the pitot formula give me?

Q (gpm) = 29.83 · C · d² · √P, where C is the discharge coefficient (typically 0.9 for a smooth-bore hydrant outlet), d is the orifice diameter in inches, and P is the pitot pressure in psi. NFPA 291-2022 standardises this method for hydrant flow testing.

Sprinkler design — area × density?

Required pump flow Q = area × density. Per NFPA 13-2025 hazard classes: Light Hazard ≈ 0.10 gpm/ft², Ordinary Hazard Group 1 ≈ 0.15 gpm/ft², Extra Hazard ≈ 0.30+ gpm/ft². Apply over the most-remote 1500–2500 ft² area.

When should I commission a real test?

Hydrant flow tests are NFPA 291-required every 5 years; sprinkler system flow at least annually per NFPA 25. The calculator helps with design and verification — it doesn't replace witnessed tests for life-safety certification.

Fire Safety – Extinguisher, Hydrant Flow

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12Fire Extinguisher Selector

Select the fuel involved and the tool will recommend suitable extinguishing agents and warn against dangerous mismatches (e.g., water on a Class C electrical fire).

Fire class i

Setting

Test agent (optional — see warning)

Recommended agent

—

Pictogram cheat-sheet

A 🔥📦 Combustibles B ⛽ Liquids C ⚡ Electrical D ⚙ Metals K 🍳 Oils

13Muster Time Calculator

Approximates muster time for a single muster point: detection & reaction lag + walking time, with crowd-density slowdown. Compare against your facility's emergency-response plan target.

Facility area (m²)

Personnel on site

Average walking speed (m/s) i

Distance to muster point (m)

Detection & reaction lag (s)

Effective doorway / route width (m) i

Plan target (min)

Estimated muster time

— min

—

Walking time—

Flow-capacity time at pinch—

Detection lag—

vs. target—

—

23Hydrant Flow & Sprinkler Density

Two practical fire-water tools side-by-side. Hydrant flow: NFPA 291-2022 pitot formula Q = 29.83·C·d²·√P (US gpm). Sprinkler: required pump flow from area-density (NFPA 13-2025) — Q = density × area.

Hydrant flow test (NFPA 291-2022)

Outlet diameter d (mm) 63 mm (2½″) outlet is the standard test for hydrants.

Pitot pressure P (kPa)

Coefficient of discharge C i

Flow result

— m³/h

Flow—

Status—

Sprinkler design (NFPA 13-2025)

Hazard classification

Design area (m²)

Hose-stream allowance (L/min)

Sprinkler demand

— L/min sprinklers

Density—

Total demand (sprinkler + hose)—

Pump rating recommended—

For training purposes only. Always verify with NFPA 10-2022 (extinguishers) and the site emergency-response plan / muster drill records.

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Fire Safety Tools

12Fire Extinguisher Selector

Recommended agent

Mismatch warning

Pictogram cheat-sheet

13Muster Time Calculator

Estimated muster time

23Hydrant Flow & Sprinkler Density

Hydrant flow test (NFPA 291-2022)

Flow result

Sprinkler design (NFPA 13-2025)

Sprinkler demand

Already designed a fire response?

Fire Safety Tools

12Fire Extinguisher Selector

Recommended agent

Mismatch warning

Pictogram cheat-sheet

13Muster Time Calculator

Estimated muster time

23Hydrant Flow & Sprinkler Density

Hydrant flow test (NFPA 291-2022)

Flow result

Sprinkler design (NFPA 13-2025)

Sprinkler demand

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