Can I use my fire extinguisher on an electric fire

Is it safe to use a fire extinguisher on an electric fire? Electric fires usually start from overloading, faulty circuits, worn outlets or electrical appliances. They can also start from prolonged usage of electric appliances beyond the manufacturer’s recommendations.



Turn off the electricity before fighting fires

The science behind an electric fire is simple. Most of the time, electric fires are simply Class A combustibles that have been ignited from heat coming from an electricity source. Remove that electricity source and we actually just have a Class A fire.

Before attempting to fight any electric fire, the first step is to quickly turn off the electricity. The main reason for this is that after putting out the electric fire, the fire may reignite. This is because electricity is still generating heat causing the plastic or rubbers parts of the electric appliance to reignite.

The good news is that, upon turning off the electricity, the remaining fire is usually a Class A fire from the burning plastic or rubbers. This makes it significantly easier to put out the fire.



Where did the fire extinguisher’s Class C and Class E logo go?

In Singapore, the Class C logo represent gas fires while the Class E logo represents electric fires. In America, Class C represents the electric fires. This is why there is often confusion as to what Class C represents.

Regardless of Class C or Class E, SCDF recommends that the source of fire be turned off as soon as it is safe to do so, even if it means before fighting the fire. This means turning off the gas supply or electricity. This is because both types of fire will quickly reignite if the source is not turned off.

This is also why the Class C and Class E logos have been phased out from the current Singapore Standards since the 2012 edition. Replacing the logo will be either the phrase:

“Use with care on live electrical equipment”

or

“Suitable for use on live electrical equipment up to 1000v at a distance of 1m”

If you still see the Class C or Class E logo, it is quite likely those are legacy fire extinguishers that are at least 10 years old. We urge you to replace these fire extinguishers as soon as possible.



Powder fire extinguishers are safe to use on electric fires

Generally speaking, dry powder is a poor conductor of electricity. This makes it one of the best options to fight electric fires. When the fire is blocking access to turn off the electricity, dry powder fire extinguishers will make the safest choice to fight electric fires.

Having said that, the phrase “poor conductor of electricity” does not mean powder will not completely conduct electricity. At very high voltages and close distances, it is still possible to be shocked. This is why lightning strikes can still occur even though air is a very poor conductor of electricity. It is also the main reason as to why it is required under Singapore Standards to have the phrase “Use with caution on electric fires.” on the fire extinguisher’s instruction label. While the probability is extremely low, it is still possible to be electrocuted. So turn off the electricity as soon as you can.



Singapore Standards EN3 Fire Extinguisher Dielectric Test

in Singapore Standards, water based fire extinguishers are not allowed to be used on electric fires unless they undergo the dielectric test. All Hercules water based fire extinguishers have successfully passed the dielectric test, making them suitable for fighting electric fires.

During fire fighting, there will be thick smoke and sometimes it would be impossible to see beyond the thick smoke. What happens if a fire fighter unknowingly, accidentally discharged a fire extinguisher at a live electric current? Would he be electrified? Hence, the dielectric testing was created so that in the event a fire fighter accidentally discharge the fire extinguisher onto a live electric fire, he would still be reasonably safe.

In the dielectric test, a live voltage is set up to test the possibility of the fire extinguisher being electrified upon direct discharge. A rectangular metal plate is placed at a distance of 1m from the fire extinguisher. Upon discharge, if the circuit is closed and the ammeter detects a live current, the test is considered to have failed. If no current is detect, the test would be considered to be successful. This test is conducted under safe conditions in a sterile laboratory so we recommend everyone not to replicate the test without professional aid.

Fire Extinguisher dielectric test
How the dielectric diagram looks like in the EN3 Standards

Upon successfully passing the test, the instruction label on the water based fire extinguisher will have the words “Suitable for use on live electrical equipment up to 1000v at a distance of 1m”.



Use with care for live electrical equipment

Whether you are using a powder or water based fire extinguisher on live electrical equipment, it should be done with caution. Similar words will also appear on a powder fire extinguisher’s instruction label.

Realistically speaking, during fire fighting, nobody would be trying to measure the current with an ammeter amidst the chaos. How would anyone know if the current is up to 1000v? Just like a lightning strike, if the potential difference is great enough, even air is a conductor for electricity. This is why, the number one rule for fighting live electrical fires starts with turning off the electricity. We want to keep ourselves as safe as possible and reduce the risk of being electrified.



Maintenance of equipment is just as important

Old electrical appliances have a higher probability of starting a fire due to aging components. It could be a worn out safety component or simply exposed wiring. The best way of fighting an electric fire is not to let it happen in the first place.

Avoid overloading power sockets and repair or replace electrical appliances immediately the moment they show signs of damage. Most importantly, look out for the Singapore Mark. This mark is not on many of the online ecommerce shops so keep a look out for them.

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