Why does my fire extinguisher hiss when I check it?

A hiss can indicate pressure release, movement at the nozzle, or a unit that has been disturbed. Because these extinguishers are pressurised, any unexpected sound should be treated cautiously and you should not try to dismantle the valve or cylinder. fileciteturn0file4turn0file11

1. Stop handling the extinguisher and place it upright. Listen to whether the sound continues without being moved.
2. Inspect the nozzle, valve area and base for dust or powder. Any sign of discharge suggests the unit may not be ready for use.
3. Check for impact marks or a loose fitting. A dropped or knocked extinguisher may hiss if the seal is compromised.
4. Do not press the handle, remove the pin or loosen the valve. The manuals say not to tamper with parts of the extinguisher. fileciteturn0file4turn0file11
5. If the sound continues, move the unit to a safe area and monitor it visually only. Do not rely on it for emergency use until it has been assessed.

Stop using the extinguisher immediately if hissing continues, powder appears, or the cylinder seems damaged. If the problem remains unresolved, contact the retailer or store where the product was purchased.