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Extinguisher
published on 26/03/2026

How to Detect and Extinguish Class A and Class D Fires

Not all fires are the same. The class of a fire determines what materials are burning, how it behaves, and, critically, how it should be extinguished. Using the wrong approach can make a fire worse rather than better.
This guide covers two distinct fire classes: Class A fires, the most common type found in everyday environments, and Class D fires, a rarer but highly hazardous category involving combustible metals.
Understanding both is essential for effective fire safety planning in commercial and residential settings.

Class A Fires

What Is a Class A Fire ?

A Class A fire involves solid combustible materials of an organic nature, including wood, paper, cloth, rubber and certain plastics. These fires are commonly found in environments such as offices, schools, retail spaces and homes, where such materials are widely present.

They are typically easy to recognise due to visible flames, smoke and the presence of ash as the materials burn. Common ignition sources include naked flames, electrical heat sources, cigarettes, candles and heaters. While controlled uses of these materials, such as in fireplaces or bonfires, can be safe, uncontrolled ignition can cause fires to spread rapidly.

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How to Detect a Class A Fire ?

Class A fires are among the most common types of fire, typically involving everyday combustible materials such as paper, wood and textiles. While these materials are often harmless in controlled environments, they can quickly become dangerous if ignited unintentionally. Key indicators include visible flames, the smell of burning organic material, smoke, and the presence of ash. 

1 Visible flames
2 The smell of burning organic material
3 Smoke
4 The presence of ash

In commercial settings, smoke detectors and fire alarm systems are essential for early detection before a fire has the chance to spread.

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How to Extinguish a Class A Fire ?

Class A fires can be extinguished using water, foam or dry powder fire extinguishers. Water extinguishers are the most common choice as they cool the burning material and remove the heat source. Foam extinguishers work by smothering the fire and preventing re-ignition. It is important never to use a CO₂ extinguisher on a Class A fire, as it is not effective on solid combustible materials.

How to Prevent Class A Fires ?

Preventing Class A fires starts with good housekeeping and risk awareness. Combustible materials such as paper, textiles and waste should be stored safely and kept away from potential ignition sources. Regular cleaning, safe storage practices and proper waste management all help reduce the risk of fire.

It is also important to ensure that heat sources, electrical equipment and open flames are properly managed and maintained. By identifying potential risks and taking preventative measures, businesses and homeowners can significantly reduce the likelihood of a Class A fire and improve overall fire safety.

Class D Fires (Combustible Metals)

What Is a Class D Fire ?

A Class D fire is characterised by the presence of burning metals. Only certain metals are flammable, and examples of combustible metals include : 

1 Sodium
2 Potassium
3 Uranium
4 Lithium
5 Plutonium
6 Calcium
7 With the most common Class D fires involving magnesium and titanium

Although it usually takes extreme heat to ignite metal, once a fire has been ignited it can spread very quickly and develop into an extremely dangerous and destructive blaze. Sodium, for example, is a highly reactive element which burns immediately on contact with air or water, resulting in explosions and making it particularly hazardous.

As most metals are relatively unlikely to combust, the most common types of Class D fire occur in environments where metal 'fines', fine particles or dust, are found. This includes laboratories, warehouses, factories and manufacturing facilities that cut, drill or mill metals. Places that process aluminium, for example, and therefore contain significant quantities of aluminium dust, are more prone to Class D fires.

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How to Extinguish a Class D Fire ?

The best and only recommended way to extinguish a Class D fire is to use a dry powder fire extinguisher. This works by smothering the fire and the oxygen within it, while also absorbing the heat contained within the fire, eventually leading to its extinction. Powder fire extinguishers also stop the burning metal or powder from spreading, reducing the overall damage caused by the fire. This is particularly useful in environments containing metal dust or shavings. 
 

Metal fires are often among the most hazardous because people are unaware of how to combat them safely and effectively. It is extremely dangerous to use water on a Class D fire, as metals such as sodium will react further with water, acting as an accelerant and making the fire significantly worse.

How to Avoid Class D Fires ?

Storing combustible metals in safe, secured containers is an effective way of reducing the risk of Class D fires. However, as most metal fires occur during manufacturing processes when metal fines are present, prevention requires a more comprehensive approach for commercial environments, particularly those involving the processing, drilling and cutting of combustible metals.

This means undertaking regular and comprehensive fire risk assessments and carrying out any remedial action necessary to remove or reduce hazards. It is also essential to ensure that fire safety systems are in place, including fire alarms, practised fire drills and emergency lighting, and that dry powder fire extinguishers are installed and regularly maintained throughout the premises.

Protect Your Premises from Every Class of Fire

Don't wait for an inspection or an incident to act. Contact Scutum today to arrange your fire risk assessment, fire extinguisher installation or fire safety review, and ensure your property is protected against every class of fire, from the most common to the most hazardous.

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