Fire extinguishers are essential devices for fire prevention and protection. They can help you control or put out small fires before they become large and dangerous. However, not all fire extinguishers are the same. Different types of fire extinguishers are designed to fight different classes of fire, and using the wrong one can be ineffective or even hazardous.
In this article, we will compare two common types of fire extinguishers: water and dry powder. We will explain what they are, how they work, what kind of fires they can extinguish, and what are their pros and cons. We will also give you some tips on how to choose the right fire extinguisher for your situation.
Key Takeaways
- Water fire extinguishers are suitable for Class A fires involving ordinary combustible materials like wood, paper, cloth, rubber, and plastics.
- Dry powder fire extinguishers are suitable for Class B fires involving flammable liquids like petrol, oil, paint, and solvents; Class C fires involving flammable gases like propane, butane, and methane; and Class D fires involving combustible metals like magnesium, lithium, and sodium.
- Water fire extinguishers work by cooling down the burning material and preventing re-ignition. Dry powder fire extinguishers work by smothering the fire and creating a barrier between the fuel and the oxygen.
- Water fire extinguishers have the advantages of being cheap, easy to use, environmentally friendly, and effective on deep-seated fires. However, they have the disadvantages of being heavy, bulky, prone to freezing, and ineffective on electrical or flammable liquid/gas/metal fires.
- Dry powder fire extinguishers have the advantages of being versatile, lightweight, compact, resistant to freezing, and effective on electrical or flammable liquid/gas/metal fires. However, they have the disadvantages of being messy, corrosive, toxic, hard to clean up, and ineffective on deep-seated fires.
What are Water Fire Extinguishers?
Water fire extinguishers are the most common and basic type of fire extinguishers. They contain pressurized water as the extinguishing agent. They are usually red in color with a white band or label.
Water fire extinguishers are suitable for Class A fires involving ordinary combustible materials like wood, paper, cloth, rubber, and plastics. These materials burn with a glowing flame and leave behind ash or char.
Water fire extinguishers work by cooling down the burning material below its ignition temperature and preventing re-ignition. They also create steam that helps to suffocate the fire by displacing oxygen.
Water fire extinguishers come in different sizes and capacities. The most common ones are 6 liters or 9 liters. They have a discharge time of about 30 seconds to 60 seconds and a range of about 4 meters to 10 meters.
Some water fire extinguishers may also contain additives that enhance their performance or usability. For example:
- Antifreeze additives prevent the water from freezing in cold temperatures.
- Wetting agents reduce the surface tension of water and make it penetrate deeper into the burning material.
- Film-forming foams create a layer of foam on top of the water that seals off the fuel from oxygen.
What are Dry Powder Fire Extinguishers?
Dry powder fire extinguishers are also known as ABC or multi-purpose fire extinguishers. They contain pressurized dry chemical powder as the extinguishing agent. They are usually red in color with a blue band or label.
Dry powder fire extinguishers are suitable for Class B fires involving flammable liquids like petrol, oil, paint, and solvents; Class C fires involving flammable gases like propane, butane, and methane; and Class D fires involving combustible metals like magnesium, lithium, and sodium. These materials burn with a bright flame and do not leave behind ash or char.
Dry powder fire extinguishers work by smothering the fire and creating a barrier between the fuel and the oxygen. They also interfere with the chemical reaction of combustion by breaking down the free radicals that sustain the flame.
Dry powder fire extinguishers come in different sizes and capacities. The most common ones are 1 kg or 2 kg. They have a discharge time of about 8 seconds to 25 seconds and a range of about 2 meters to 5 meters.
Some dry powder fire extinguishers may also contain specific powders that target specific metals or gases. For example:
- Sodium chloride powder is effective on sodium or potassium fires.
- Copper powder is effective on lithium fires.
- Monnex powder is effective on flammable gas fires.
Pros and Cons of Water Fire Extinguishers
Water fire extinguishers have the following advantages:
- They are cheap and widely available.
- They are easy to use and operate.
- They are environmentally friendly and biodegradable.
- They are effective on deep-seated fires that require a lot of cooling.
Water fire extinguishers have the following disadvantages:
- They are heavy and bulky to carry and store.
- They are prone to freezing in cold temperatures, unless they contain antifreeze additives.
- They are ineffective on electrical or flammable liquid/gas/metal fires, and may even spread or worsen the fire.
- They may cause scalding or electrocution if sprayed on live wires or equipment.
Pros and Cons of Dry Powder Fire Extinguishers
Dry powder fire extinguishers have the following advantages:
- They are versatile and can be used on multiple classes of fire.
- They are lightweight and compact to carry and store.
- They are resistant to freezing in cold temperatures.
- They are effective on electrical or flammable liquid/gas/metal fires, and can quickly knock down the flame.
Dry powder fire extinguishers have the following disadvantages:
- They are messy and leave behind a lot of residue that can damage equipment or furniture.
- They are corrosive and may cause rust or corrosion on metal surfaces.
- They are toxic and may cause respiratory or skin irritation if inhaled or contacted.
- They are hard to clean up and may require special disposal methods.
- They are ineffective on deep-seated fires that require a lot of cooling.
How to Choose the Right Fire Extinguisher
Choosing the right fire extinguisher depends on several factors, such as:
- The class of fire that you may encounter in your location or situation.
- The size and severity of the fire that you may face.
- The availability and accessibility of the fire extinguisher.
- The ease and safety of using the fire extinguisher.
Here are some general guidelines on how to choose the right fire extinguisher:
| Class of Fire | Suitable Fire Extinguisher | Unsuitable Fire Extinguisher |
|---|---|---|
| Class A | Water, foam, wet chemical, dry powder | CO2, wet chemical (for cooking oil) |
| Class B | Foam, dry powder, CO2, wet chemical (for cooking oil) | Water, wet chemical (for other liquids) |
| Class C | Dry powder | Water, foam, CO2, wet chemical |
| Class D | Special dry powder | Water, foam, CO2, wet chemical |
| Electrical | Dry powder, CO2 | Water, foam, wet chemical |
| Size of Fire | Suitable Fire Extinguisher Capacity |
|---|---|
| Small (e.g. waste bin) | 1 kg or 2 kg dry powder; 2 kg CO2 |
| Medium (e.g. sofa) | 6 liters water; 6 liters foam; 4 kg dry powder; 5 kg CO2 |
| Large (e.g. car) | 9 liters water; 9 liters foam; 6 kg dry powder; 10 kg CO2 |
| Availability and Accessibility | Suitable Fire Extinguisher Location |
|---|---|
| High (e.g. office, shop, school) | Near exits, corridors, stairways, fire points |
| Low (e.g. home, car, boat) | Near kitchen, garage, bedroom, engine room |
| Ease and Safety of Use | Suitable Fire Extinguisher Type |
|---|---|
| Easy (e.g. novice user) | Water, foam |
| Moderate (e.g. trained user) | Dry powder, CO2 |
| Difficult (e.g. expert user) | Wet chemical, special dry powder |
Conclusion
Water and dry powder fire extinguishers are two common types of fire extinguishers that have different characteristics, applications, advantages, and disadvantages. It is important to know how to use them properly and safely in case of a fire emergency.
Water fire extinguishers are suitable for Class A fires involving ordinary combustible materials. They work by cooling down the burning material and preventing re-ignition. They are cheap, easy to use, environmentally friendly, and effective on deep-seated fires. However, they are heavy, bulky, prone to freezing, and ineffective on electrical or flammable liquid/gas/metal fires.
Dry powder fire extinguishers are suitable for Class B, C, and D fires involving flammable liquids, gases, and metals. They work by smothering the fire and creating a barrier between the fuel and the oxygen. They are versatile, lightweight, compact, resistant to freezing, and effective on electrical or flammable liquid/gas/metal fires. However, they are messy, corrosive, toxic, hard to clean up, and ineffective on deep-seated fires.
Choosing the right fire extinguisher depends on the class of fire, the size and severity of the fire, the availability and accessibility of the fire extinguisher, and the ease and safety of using the fire extinguisher. You should always check the label and instructions of the fire extinguisher before using it, and follow the PASS technique: Pull the pin, Aim the nozzle, Squeeze the lever, and Sweep from side to side.
We hope this article has helped you understand the differences between water and dry powder fire extinguishers, and how to choose the right one for your fire safety needs. Remember, fire extinguishers are only meant for small fires that can be controlled easily. If the fire is too large or dangerous, you should evacuate the area and call the fire department. Stay safe and alert!
