Sprinkler systems attract more myths than any other part of fire protection. Clearing up a few of them makes it much easier to understand why certain maintenance items matter and why fit-out work needs to be reviewed.
They do not all go off at once
Each head operates independently when the heat at that head breaks its glass bulb or fuses its link. A fire in one room operates the heads over that fire. The image of an entire floor being drenched comes from cinema, not from installed systems.
Most fires are controlled by very few heads
The design intent is to control a fire while it is small, and to do it before the fire service arrives. That is why the water damage argument is usually backwards: a controlled fire with two operated heads causes far less damage than an uncontrolled one with a fire service hose attack.
What actually degrades a sprinkler system
Rarely the heads. Almost always one of these:
- A closed valve. The single most serious failure. A control valve closed for maintenance and left closed disables everything downstream. This is what tamper switches and valve position checks exist for.
- Obstructed heads. Storage stacked too high, a new partition, a suspended ceiling installed below the heads, or signage hung underneath. Spray pattern is the whole mechanism.
- Painted or damaged heads. Paint on a bulb changes its thermal response. A painted head is a replaced head, never a cleaned one.
- Changed occupancy. A system designed for an office hazard classification does not cover a storage room full of packaging. The hazard class drives the density, and the density drives the whole design.
Fit-out is where systems quietly break
Almost every serious sprinkler deficiency we find was introduced by fit-out work rather than by age. New walls create unsprinklered pockets. Ceilings move. Head positions relative to partitions stop complying. If you are changing the layout, the sprinkler design needs reviewing and resubmitting, even where the change looks cosmetic.
What to check yourself
Walk the floor and look up. Heads should be unobstructed, unpainted, free of dust caking, and clear of anything stacked or hung within the clearance below them. Then check that every control valve is open and strapped or supervised. Those two checks catch most of what we find on survey.