3 · What Goes Wrong
What Goes Wrong
Common defects and what to do
| What you find | What it probably means | What to do |
|---|---|---|
| Missing | Used, moved or stolen | Replace from spare stock, report to client |
| Obstructed / hidden | Site housekeeping | Ask site to clear it, record it, report if not fixed |
| Tamper seal broken, pin missing | May have been partly discharged | Weigh and check the gauge. If any agent is lost, recharge. Refit the pin and seal. |
| Gauge in the red (low) | Slow leak, or partly used | Recharge and find the leak (valve O-ring, gauge thread) |
| Gauge in the red (high) | Overcharged, or exposed to heat | Investigate. Do not leave in service until it's in range. |
| Gauge needle stuck | Faulty gauge | Replace the gauge, or the extinguisher |
| Weight low | Agent lost (CO₂ leaks through the valve) | Recharge. For CO₂, if the loss is beyond the permitted limit VERIFY, recharge. |
| Hose split, perished or blocked | Age, UV, insects, damage | Replace the hose |
| CO₂ horn cracked or missing | Damage | Replace with the correct non-conductive horn |
| Dents, gouges, bulging | Impact damage | Condemn if the shell is weakened (see chart) |
| Corrosion (rust, pitting, especially around the base and welds) | Wet or corrosive environment, common on chemical sites | Light surface rust: clean and monitor. Pitting or corrosion at seams: condemn. |
| Caked powder (cartridge types, or found at discharge test) | Moisture or vibration | Replace the powder; find out why moisture is getting in |
| Label illegible or missing | Weather or chemical attack | Relabel if it can be positively identified, otherwise condemn |
| Overdue discharge / hydro test | Missed service | Carry out the test, or replace |
| Wrong type for the risk | Layout changed, or it was wrong from the start | Report to the client in writing. Don't just swap it without telling them. |
| Obsolete type | Very old stock | Remove from service (see below) |
When to condemn
flowchart TD
A["Defect found"] --> B{"Shell damaged?<br/>dents at seams, bulging,<br/>cracks, pitting, fire damage"}
B -- Yes --> X["❌ CONDEMN<br/>Depressurise safely<br/>Mark 'condemned'<br/>Remove & replace"]
B -- No --> C{"Failed a hydrostatic /<br/>pressure test?"}
C -- Yes --> X
C -- No --> D{"Obsolete type, or unlisted /<br/>not to a recognised standard?"}
D -- Yes --> X
D -- No --> E{"Parts available and<br/>economic to repair?"}
E -- No --> X
E -- Yes --> F["✔ Repair / recharge<br/>re-check and return to service"]Obsolete types: take out of service
Both standards say very old designs must be removed. Examples you could still find on old sites:
- Soda-acid and chemical foam extinguishers (operated by turning upside down)
- Extinguishers with soft-soldered or riveted copper/brass bodies
- Cast iron shells
- Carbon tetrachloride / vaporising liquid (toxic)
- CO₂ extinguishers with metal horns NFPA. A metal horn conducts electricity, which is a shock risk on electrical fires.
- Halon extinguishers BS. Banned in the UK and EU except for listed critical uses (e.g. some aircraft and military applications).
Real-world ways extinguishers fail
- "It was there, but nobody could reach it." Blocked by stock, a locked cabinet, or moved.
- Powder caked solid in extinguishers on vibrating plant or vehicles. It looks fine, the gauge is green, but nothing comes out. This is exactly what the BS discharge test and the NFPA internal exam are designed to catch.
- Water extinguisher used on an electrical fire, or CO₂ used in a small room: the wrong type for the risk. This is why siting and suitability are checked.
- Gauge stuck in the green while the extinguisher is empty. Weighing catches it.
- Corrosion from the outside in on chemical plants, often hidden at the base or under the bracket. Lift it and look underneath.
Key takeaways
- Most defects come down to missing, used, leaking, blocked or corroded.
- Damaged shell = condemn, no exceptions.
- Report wrong type or wrong place in writing. The client must decide.
- Lift it, weigh it, look underneath it. The gauge alone isn't enough.