Class D Fires involve the ignition of combustible metals such as lithium, magnesium, and sodium. This type of fire commonly happens in industrial or laboratory environments.
Fires in the UK are split into 6 fire classes due to their different sources, behaviours and extinguishers required. Although they all share heat and oxygen as their common elements, they each need a separate material to cause ignition.
Fires should only be handled by untrained individuals if the fire is small and if they are sure of what is causing it to burn.
Having the appropriate extinguisher on site can prevent extensive damage from occurring and can keep everyone safe. The wrong extinguisher, however, can cause a further explosion which may result in injury or even death.
What is a Class D Fire?
When a fire involves flammable metal, it is considered a Class D fire. Combustible metals include potassium, titanium, lithium, magnesium, and aluminium.
Class D fires will typically occur in industrial and commercial sites where metal is either drilled or cut. Examples include warehouses, laboratories and factories where fine metal powder can be found.
In every fire situation, there needs to be heat and oxygen, which along with the third element, causes the fire to be lit.
Class D fires burn when intense heat hits combustible metals, which not all metals are. Fires such as these are more common in metal shavings rather than huge pieces of metal which, understandably, would take a long time to heat sufficiently to point of ignition.
Fire Symbol
The fire symbol for Class D is the letter D and an image of a wheel with flames coming out of the top.
See Also: Extinguisher Colour Codes – Identification of fire extinguishers using the label colour coding system.
About Class D Fire Extinguishers
Class D fires should be controlled using a Dry Powder fire extinguisher.
Using the wrong extinguisher can prove very dangerous. For example, throwing or spraying water onto a fire involving metals, will increase the flames. This can quickly escalate the fire meaning it becomes a much more serious situation. When combustible metals are involved, it is essential to quash the oxygen supply as soon as possible.
Dry Powder Fire Extinguishers
Dry powder extinguishers contain either sodium or potassium bicarbonate and tackle both the heat and oxygen sources.
They work by spraying a powder which smothers the fire and reduces the amount of oxygen being supplied to it. The powder also brings down the overall temperature which in turn causes the fire to decrease and die out.
The dry powder extinguishers can also be used on type A, B and C fires.
How to Extinguish a Class D Fire?
To extinguish a Class D fire safely and responsibly, you should only use a dry powder extinguisher. Never use a water extinguisher on a metal fire. This will cause the fire to worsen and spread rapidly.
Any work environment that deals with metal in any form should have a dry powder extinguisher to hand. It should be checked regularly and staff should be trained on how to use it and why this one is used in place of any other one. The dry powder, once released, gets to work on both the oxygen and the heat sources.
When dealing with Class D fires, you need to eliminate the heat and oxygen from the fire as soon as possible. Any workplace where drilling or cutting of metal takes place should have dry powder extinguishers in easy to access areas.
How to Use a Dry Powder Extinguisher
A dry powder extinguisher has to be used in a safe and controlled manner.
Once the powder is discharged, visibility can be impaired, particularly if it is used inside a building. The people in the room should also try to breathe through their noses where possible. This is because the powder can act as an irritant, causing breathing issues.
- Get hold of the extinguisher and release the safety pin.
- Make sure to stand at a safe distance.
- Point the nozzle to the base of the fire and move in a horizontal direction.
- Keep going until the foam has smothered the fire.
The fire should be observed for any signs of reignition until you are positive it has been put out permanently.
Types of Extinguishers That Should Not Be Used
Water fire extinguishers, or water in any form, should never be used on a Type D fire.
This includes extinguishers, hoses and buckets of water. Throwing water onto a metal-based fire will make the fire angrier and bigger.
Certain metals are extremely reactive to water particles and when the two are combined an explosion is possible.
Class D Fire Prevention
There are practical steps that can be taken to help with Class D fire prevention. We outline these below:
- In a workplace where metal shavings or dust particles accumulate, regular cleaning should take place.
- Equipment should be regularly cleaned and checked for any build-up of metal particles.
- Metals should be stored responsibly.
- Carry out a regular fire risk assessment with all staff.
