| name | fire-suppression |
| description | Fire suppression systems — sprinkler design (NFPA 13), clean agent (FM-200/Novec 1230/CO₂), foam suppression (NFPA 11), water mist (NFPA 750), hydraulic calculations, hazard classification, pipe sizing, storage requirements. |
| metadata | {"priority":7,"promptSignals":{"phrases":["fire suppression","sprinkler system","NFPA 13","clean agent fire","FM-200","CO2 suppression"],"minScore":3}} |
Fire Suppression Systems — Complete Skill
Hazard Classification (NFPA 13)
Light Hazard: offices, churches, hospitals, educational; low combustible content
Ordinary Hazard Group 1: parking garages, laundries, bakeries; moderate combustibles
Ordinary Hazard Group 2: machine shops, auto showrooms, woodworking; higher combustible load
Extra Hazard Group 1: printing, die casting, metalworking with flammable liquids
Extra Hazard Group 2: painting operations, open flammable liquid handling; highest sprinkler demand
High-Piled Storage (NFPA 13 Chapter 20):
Commodity classes I–IV and rack storage; in-rack sprinklers may be required above 3.7 m (12 ft) storage height
Sprinkler System Design (NFPA 13)
Design Density and Area of Application
| Hazard | Density [mm/min] | Design Area [m²] |
|---|
| Light | 4.1 | 139 |
| Ordinary Group 1 | 6.1 | 139 |
| Ordinary Group 2 | 8.2–10.2 | 139–186 |
| Extra Hazard 1 | 16.3 | 232 |
| Extra Hazard 2 | 24.5 | 279 |
Sprinkler coverage area per head:
Light/Ordinary: max 20.9 m² (225 ft²) per sprinkler
Extra Hazard: max 9.3 m² (100 ft²)
Maximum spacing: 4.6 m (15 ft) between heads
Hydraulic Design (Pipe Sizing)
Hazen-Williams equation (most common for fire suppression):
P_loss = 6.05 × 10⁵ × Q^1.85 / (C^1.85 × d^4.87) [bar/m; Q in L/min; d in mm]
C = pipe roughness factor: steel (new) C = 120; galvanized C = 100; CPVC C = 150
Flow from sprinkler head:
Q = K × √P [L/min; K = K-factor [L/min/bar^0.5]; P = pressure at sprinkler [bar]]
K-factors: 57 (standard), 80, 115, 161, 202, 242, 363 (large orifice)
Most Remote Sprinkler (worst-case design):
Calculate pressure required at most remote head to achieve design density
Work back to supply source including all pipe losses, elevation changes, valve losses
Pressure at most remote head:
P_min = (Q_required / K)² [bar; Q_required = density × coverage area per head]
Water Supply Requirements
Total system flow (demand):
Q_total = density × design area + hose stream allowance
Hose allowance: 250–950 L/min (65–250 GPM) depending on hazard
Duration: Light/Ordinary: 60 min; Extra Hazard: 60–90 min; Storage: up to 120 min
Supply check: fire pump curve + static pressure at connection ≥ system demand curve
System types:
- Wet pipe: always filled with water; fastest response; most common
- Dry pipe: pressurized air; for unheated spaces; activation slower (≤ 60 s)
- Pre-action: requires secondary detection + sprinkler activation; data centers, museums
- Deluge: all heads open; open nozzles; high-hazard processes
Clean Agent Suppression (NFPA 2001)
FM-200 (HFC-227ea) — Heptafluoropropane
Design concentration: 7.0–8.0% by volume in protected space (NOAEL = 9% for human safety)
Extinguishing mechanism: primarily physical heat absorption (thermodynamic); minor chemical inhibition
Required agent mass:
W = (V × ρ_agent / 100) × C / (100 - C)
where V = room volume [m³]; ρ_agent = FM-200 vapor density [kg/m³]; C = design concentration [%]
FM-200 density at 21°C: ρ_v = MW/22.4 × (273/294) = 7.08/22.4 × 0.929 = 0.294 kg/m³
Discharge time: NFPA 2001: ≤ 10 seconds for Class A/B; ≤ 10 seconds for Class C
Storage: liquid in cylinders at 25 bar (360 psi); super-pressurized with nitrogen
Novec 1230 (FK-5-1-12) — NFPA 2001
Design concentration: 4.2–5.9% (NOAEL = 10%; large safety margin)
Lower concentration → smaller cylinder footprint vs. FM-200
Zero ODP; GWP = 1 (very low) → preferred environmental option over HFCs
CO₂ Suppression (NFPA 12)
Total flooding concentration: 34% for most Class B/C hazards; 50% for gaseous fuel (inerting)
Smothering mechanism: displaces O₂ below 15% → fire extinguishment
Design quantity:
V_CO₂ = X × V_room [m³ at STP; X = volume fraction from NFPA 12 table]
Mass: m = V_CO₂ × 1.977 kg/m³ (CO₂ density at STP)
Hazard to personnel: immediately dangerous to life and health (IDLH) at 4%; CO₂ systems require evacuation alarm + pre-discharge time delay ≥ 30 s
High-pressure (HP) system: 56 bar (800 psi) cylinders; suitable for total flooding
Low-pressure (LP) system: refrigerated at -18°C, 20 bar (300 psi); large volumes (>5,000 kg)
Foam Suppression (NFPA 11)
Applications: flammable liquid storage tanks, aircraft hangars, tank farms
Foam types:
| Type | Expansion Ratio | Application |
|---|
| AFFF (aqueous film-forming foam) | 6:1–10:1 | Hydrocarbon spills, fuel tanks |
| FFFP (film-forming fluoroprotein) | 6:1 | Hydrocarbon (splash resistance) |
| AR-AFFF (alcohol resistant) | 6:1 | Polar solvents (alcohol, ketones) |
| High-expansion foam | 200:1–1000:1 | 3D confined fires, mines |
Application rate (NFPA 11):
Fixed-roof tanks: 4.1 L/min/m² for AFFF; 4.1 L/min/m² for surface application
Open-top tanks: subsurface injection available with specially designed nozzles
Foam concentrate selection:
3% AFFF: mix 3% concentrate + 97% water = solution (proportioned)
6% FFFP: higher proportion; larger concentrate storage
Water Mist Systems (NFPA 750)
High-pressure water mist: P > 35 bar; droplet size Dv₀.₉ < 200 μm
Low-pressure: P < 12 bar; droplets larger; more water flow needed
Mechanisms: evaporative cooling + oxygen displacement from steam + radiant heat attenuation
Applications: machinery spaces, museums (low water damage), turbine enclosures, passenger ships (IMO MSC)
Droplet size specification:
Dv₀.₅ = 50–100 μm (volume median diameter); measured by laser diffraction
Flow rate: 1.5–3 mm/min application density (lower than sprinklers for some hazards)
Pipe Sizing and Pressure
Pipe schedule for fire suppression:
Schedule 10 or 40 steel (ASTM A795 or A135); black steel standard; galvanized in corrosive areas
Minimum pipe diameter: 25 mm (1 in) branch; 38 mm (1.5 in) cross-main minimum
Pressure regulators:
Required when pressure exceeds 12.1 bar (175 psi) at sprinkler heads
Pressure-reducing valves at zone control points
Fire pump (NFPA 20):
Types: horizontal split-case, vertical turbine, end-suction
Net positive suction head available (NPSHa) > NPSHr
Pump rated at 150% flow at 65% of rated pressure; churn pressure ≤ 140% rated
Standards
| Standard | Scope |
|---|
| NFPA 13 | Installation of sprinkler systems |
| NFPA 2001 | Clean agent fire extinguishing systems |
| NFPA 12 | Carbon dioxide extinguishing systems |
| NFPA 11 | Low-, medium-, high-expansion foam |
| NFPA 750 | Water mist fire protection systems |
| NFPA 20 | Installation of stationary pumps for fire protection |
| FM Global DS 2-0 | Installation guidelines — FM Global |
Output
Provide: hazard classification (NFPA 13 Light/Ordinary/Extra Hazard), system type (wet pipe/dry pipe/pre-action/deluge), design density [mm/min] and area [m²], K-factor and spacing of sprinklers, most remote head pressure [bar] and flow [L/min], total system demand [L/min] and duration [min], fire pump required flow and pressure, clean agent type and design concentration [%] (if applicable), agent mass required [kg] (if clean agent), CO₂ quantity [kg] and ventilation delay (if CO₂), foam type and application rate [L/min/m²] (if foam), pipe sizes and Hazen-Williams C-factor, and applicable standard (NFPA 13, NFPA 2001, NFPA 12).
