# 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.

## 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**.

## Frequently asked questions

### Which class does an office fall into?

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.

### Can the hazard class change after a building is designed?

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.

## Sources

- [IS 15105](https://standards.bis.gov.in/website/published-standards/department-wise) — Design and installation of fixed automatic sprinkler systems
- [NBC 2016, Part 4](https://www.bis.gov.in/standards/national-building-code/?lang=en) — Fire and life safety

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Source: https://hagerstone.com/glossary/sprinkler-hazard-classification