Sprinkler Hazard Classification: Light, Ordinary and High
Sprinkler hazard classification groups occupancies by how quickly and intensely a fire in them is likely to develop — broadly light, ordinary and high hazard — and that class sets the water density, the area of operation, and therefore the pump and tank size the system needs.
By Dhruv Agarwal · · 1 min read
Why it matters
The hazard class is the first input to a sprinkler design. It decides how much water must be discharged, over what area, for how long — which sizes the pump room and the fire water tank before any pipe is drawn.
How it works in practice
| Class | Typical occupancies | Effect on design |
|---|---|---|
| Light hazard | Offices, hospitals, hotels | Lowest water density |
| Ordinary hazard | Manufacturing, retail, some storage | Higher density and area |
| High hazard | High-piled storage, flammable materials | Highest demand |
Common mistakes
- Designing for today's use only. A change of use can outgrow the system.
- Ignoring storage height. Racking height changes the hazard significantly.
- Sizing the tank before the class is fixed. The tank depends on it.
Standards referenced
Sprinkler design under IS 15105. Fire and life safety under NBC 2016, Part 4.
Standards referenced
- IS 15105 — Design and installation of fixed automatic sprinkler systems (Bureau of Indian Standards)
- NBC 2016, Part 4 — Fire and life safety (Bureau of Indian Standards)
Frequently asked
Offices are typically light hazard. Storage, manufacturing and areas with combustible goods move into ordinary or high hazard, depending on what is stored and how high it is stacked.
Yes, and it catches owners out. Converting office space to storage, or stacking goods higher in a warehouse, can raise the hazard class beyond what the pumps, tank and pipework were designed for.
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