The prevention of danger due to overpressurization of fire extinguishers shall be achieved for all foreseeable circumstances either by eliminating the hazard by the design, or by providing a protective device.
The risk of external fire shall be adequately considered according to the type of fire extinguisher.
Due to the fact that portable extinguishers are very wide-spread and are also consumer products, their possible misuse must be carefully assessed. Written instructions alone cannot be regarded as sufficient.
Examples
In general the risk of over-filling is significant for cartridge type fire extinguishers with a water based content, which are manually (re-)filled. EN 3-8 contains a dedicated overfill pressure test to verify the design for this risk.
External fire will cause high risks for CO2 fire extinguishers (cylinders) due to the physical behaviour of CO2 at elevated temperatures. EN3-9 therefore prescribes a bursting disc safety device for this type of extinguisher