3 · What Goes Wrong
Working safely on site
Fire systems are designed to save lives, but servicing them has its own hazards. This page covers the hazards common to all equipment. Each module adds its own.
The main hazards
| Hazard | Where you'll meet it | What can go wrong | Control |
|---|---|---|---|
| Stored pressure | Extinguishers, gas cylinders, pressurised pipework | Parts or cylinders released at high force | Depressurise before dismantling, never point a valve at anyone, use the correct tools |
| Water under pressure | Sprinkler, deluge, hydrant, hose reel | Pipework whipping, flooding, damage to stock or plant | Know where the isolation valves are and open/close slowly |
| Accidental discharge | Gas suppression, deluge, foam | Room flooded with agent, people trapped, plant damage | Mechanical and electrical isolation before work; follow the CTT exactly |
| Asphyxiation | CO₂ and inert gas protected rooms | Unconsciousness and death in seconds at CO₂ design concentrations | Never enter after a discharge until ventilated and cleared; lock-off |
| Working at height | Detectors, sprinkler heads, high-level valves | Falls | Right access equipment, inspected, with a permit if required |
| Manual handling | Extinguishers (up to ~20 kg), cylinders (60 kg+) | Back injuries | Trolleys and cylinder trucks, team lifts |
| Hazardous substances | Foam concentrate, powder, wet chemical | Skin/eye irritation, inhalation | COSHH data sheet, gloves, eye protection, dust control |
| Explosive atmospheres | Chemical plant areas (ATEX zones) | A spark from a tool or phone ignites flammable vapour | Only certified equipment in zoned areas; hot work permit; gas testing |
| Live electricity | Alarm panels, pump starters, release panels | Shock | Isolate and prove dead; only competent people work on mains |
Permit to work, isolation and impairment
On an industrial site like Dow, you don't touch anything without a permit. A permit tells you:
- exactly what you're allowed to work on,
- what has been isolated, and by whom,
- what hazards are present, and what PPE and gas tests are needed,
- when it expires.
flowchart TD
A["Need to work on a fire system"] --> B["Request permit from site"]
B --> C["Site checks hazards<br/>· area classification<br/>· isolations<br/>· gas test if needed"]
C --> D{"Will fire protection<br/>be impaired?"}
D -- Yes --> E["Impairment procedure:<br/>notify control room, insurer if required,<br/>fire watch, tag the valve/panel"]
D -- No --> F
E --> F["Permit issued & signed<br/>you're briefed"]
F --> G["Do ONLY the work on the permit"]
G --> H["Restore · test · de-impair"]
H --> I["Hand back & sign off permit"]What goes wrong: real-world patterns
- Valve left closed after maintenance. The system looks fine but can't deliver water. This is the single biggest reason sprinklers fail to control fires.
- Isolation not removed. An alarm zone stays disabled for weeks because nobody restored it.
- Wrong item worked on. Two similar valves, wrong one isolated. Always confirm the tag/ID.
- Accidental gas discharge during maintenance. Usually because the actuator wasn't removed or isolated first.
- Records not completed. The next engineer doesn't know a defect was found.
Key takeaways
- No permit, no work.
- Know what you've isolated and put it back.
- If anything doesn't match the permit or the drawing, stop and ask.