Class A fire extinguishers are used in dealing with class A types of fires. These fires involve organic solids such as paper, wood, textile, and plastics. These solids are the most common and abundant types of fuel and it is difficult to do away with them in the construction of premises. This is the reason that class A fires are the most common accidental fires that are reported statistically. Luckily, these fires are easy to extinguish.
Class A Fire Extinguishers
These extinguishers commonly use water, foam, dry powder, or wet chemical as their working component. Most people are familiar with these kinds of extinguishers. It is important to understand how Class A fire extinguishers work and the kinds of fires they are best suited for in case an emergency occurs.
Class A extinguishers are more likely to be used in buildings or premises constructed of wood and organic materials. These include offices, hospitals, schools, and residential houses.
Generally, fire extinguishers are rated for the types of fire they are effective in putting out. The ratings are based on the material they can effectively extinguish. To qualify for a class A rating, the extinguisher must pass the test for putting out certain test materials that include wood panels and shredded paper.
Types of Class A Fire Extinguishers
The most common types of extinguishers for class A fires are water extinguishers. Water extinguishers put out the fire by taking away the heat from the fire. This causes the fire to burn more slowly until the flames are extinguished. Water extinguishers can either be jet, spray, mist, water with additives, or water mist extinguishers.
Water jet extinguishers spray large volumes of water effectively putting out flames using the cooling effect. Water spray extinguishers use fine sprays of water droplets. The spray jets cover a larger area than water jet extinguishers.
Water mist extinguishers are similar to water spray extinguishers but have finer water droplets. The smaller droplets absorb heat faster from the fire due to increased surface area. Water extinguishers with additives use water with foam chemical additives. The additives allow the water to soak into the burning solids much more effectively.
Water extinguishers have a red label.
Form extinguishers are foam-based and can soak into the burning fuel. Form extinguishers also have a cooling effect on the fire and this further increases the extinguishing effect.
Dry Powder Extinguishers
Dry powder extinguishers create a barrier between the air and the fire leading to fire oxygen starvation. These extinguishers should not be used in enclosed spaces because the powder can easily be inhaled and pose a health risk.
The powder also creates a mess that is difficult to clean.
Dry powder extinguishers are more suitable in cases where the fire is near an electric source. Many dry-powder extinguishers can be used safely when in contact with up to 1000 volts of electricity. Water extinguishers may cause electric shock hazards in such cases.
Powder extinguishers have a blue label.
Wet-chemical extinguishers are rarely used for class A fires even though they are effective. They work by creating a layer of foam around the fire. This minimizes the oxygen available to fuel the fire. The chemical spray additionally cools the fire. Wet-Chemicals are very ideal in cases of very high-temperatures and where the other class A extinguishers may not be effective.
Wet chemical extinguishers have a yellow label.
Which class A extinguishers should be used?
The type and volume of burning materials in a class A fire can determine the type of class A extinguisher to use.
Wood is normally a component in most fires since it is a primary component in buildings and furniture. A water extinguisher is best suited for wood since wood can quickly absorb the water and prevent the recurrence of the fire. Dry powder extinguisher is less effective on wood since uncooled embers of wood and charcoal formed can easily re-ignite.
When plastic burns, it melts creating fuel for the fire. Water extinguishers are normally effective in putting out plastic fires when the plastic is low in quantity. In cases where there is a large quantity of plastic burning, a lot of combustible liquid plastic floats on the water since plastic is less dense than water. This can easily spread the fire farther. In such a case, a dry powder class A fire extinguisher would be most suitable.
Paper fires burn and spread very quickly. Water extinguishers are very effective for such fires. Spray and mist extinguishers are however much more effective to contain a fast-spreading fire since they cover a larger area within a short time.
This kind of fire also spreads very fast. Water extinguishers are the most effective for textile fires since textiles are absorbent and retain water.
Storage and Placement of Class A Fire Extinguishers
Extinguishers need to be conspicuously located in case of an emergency. Water and foam fire extinguishers are usually placed near the building and premise floor exits. Dry-powder and wet-chemical extinguishers are normally placed near the location that is prone to fire.
It is important to have the right class A fire-extinguisher for the job. But of course, the simplest, the most obvious and the most effective way to prevent a class A fire is to manage the organic materials that commonly cause the fire.