What is the 35kVa Dielectric Test Rating?
Fire Extinguisher Test Rating
We all know that water and electricity don’t mix. Water is quite a good conductor of electricity, and it’s always been great practice to keep the two things apart.
But accidents can happen. Take my favourite little example: your waste bin starts burning for some reason. Justifiably, you reach for a water or foam fire extinguisher and start to tackle the fire. You weren’t to know there was a live double socket behind there! The jet of water hits the live electrics, and 240V is conducted up the stream of water, through the valve, into the handles and right into your hand. Ouch.
Most water extinguishers and foam fire extinguishers have now passed the 35kVa dielectric test, making them safe for inadvertent use on live electrical equipment up to 1000V. This is mostly done by using a spray nozzle rather than a jet, and breaking up the stream of water, thus stopping it conducting electricity. In the test, the stream of extinguishant hits a metal plate charged to 1000V, and no electricity is conducted back to the fire extinguisher.
So why the ‘inadvertent’ word, I hear you ask… Well, next time you wash the car or mop a floor, fill your bucket up with water nearly to the top. Most buckets are 10l capacity, and a 9l water holds nearly as much liquid. Take it outside and tip it on a level section of tarmac or concrete. It goes a long way! The same thing happens when you fight a fire using a water or foam extinguisher – it’s called ‘pooling’, and is dangerous as the pool could conduct electricity if it gets in contact with live electrical equipment, and if the water runs back and gets your feet wet, ZAP! So that’s why, no matter how rigorously they are tested, we never recommend specifying wet extinguishers for use where a significant live electrical risk is present.
With extinguishers like CO2 and Powder available, these are both effective extinguishers and completely safe on live electrics – that’s why we always recommend these in situations where there is a live electrical risk present. Have a look around your premises – if there are live electrics there always make sure these are adequately covered with CO2 or Dry Powder extinguishers.