There are various types of portable fire extinguishers available with just as many different applications each work best at. There is a lot of misinformation surrounding these uses and knowing each one's pro's and con's will allow the user to make an intelligent selection for a proper application of the best extinguisher for each situation.
It's not uncommon to hear comments referring to "Halotron" or it's predecessor, "Halon" fire extinguishers as thought to be the best type available. While it depends on the application, Halon/Halotron is not necessarily the "best" type of extinguisher for most situation. Dry chemical extinguishers also have their pro's and con's, although their biggest advantage in most portable situations, is that Dry Chemical can be far more effective and safer to use than Halon/Halotron.
HALON/HALOTRON: Halon and Halotron's biggest advantage, is it's gaseous content leaves no residue or chemical damage to the affected surface when depleted. Halon and Halotron are a very wise choice in enclosed areas where sensitive electronic equipment is present such as computer rooms and on-board fixed release systems under the hood and works best when you have more available content than dry chem. However, while this gaseous content cools the fire and removes the source of oxygen, it does not leave anything behind to prevent flare-up's and can take the oxygen right out of your lungs if in an enclosed area. Halon and Halotron also does not effectively reach far beyond it's supply source meaning you have to get in close to the fire to apply it. It also can be rendered ineffective in high wind conditions. While a Halon or Halotron extinguisher is cleaner, it can be much less effective and once the oxygen that was removed by the gas returns, if the source is still present, such as a hot wire, a hot header, leaking fuel or oil or smoldering embers, there is a very good likelihood that the fire will restart. A dry chemical covering it is DESIGNED not to allow that to happen.
DRY CHEMICAL/POWDER: Dry chem's biggest advantage is it covers the fire and physically cuts off oxygen to the source of the fire preventing it in most cases from flaring back up. It is also safer to use in enclosed areas since it does not take the oxygen out of the air. Dry chem also has the ability to effectively reach out farther putting a safer distance between the user and the fire. However, the dry chemical leaves a powdery mess behind and is acidic by nature which requires a prompt clean up to reduce any cosmetic surface damage to bare metals, especially if the powder gets wet. Typically a dry chem powder will not cause any immediate surface damage, however, if it is rated for "A" type fires, the usual agent that makes that possible is the presence of Monoammonium Phosphate, which is the agent's ability to melt and flow at 350 degrees to smother the fire. The agent "A" is more corrosive than the other agents "B", "C" and "D". Type "A" is more useful for wood and other solid combustibles. This is where a B-C extinguishers might be a better selection.
HALON/HALOTRON BEST USES: Halon and Halotron or "clean" extinguishers are best used for predictable temporary fires, such as simple carb backfires, small amounts of fuel spilled on the ground, or cigarettes burning on a carpet where you would want to extinguish the fire and move on rather than cover a large area in a more serious threat.
ABOUT HALON: The production of Halon has been banned in most countries since January 1, 1994 due to its ozone depleting substances. However, recycling of Halon 1211 allows it to remain in use, although parts availability is limited to a few manufacturers and can be an issue. Halon 1211 is still widely used in the United States, despite its high cost, with the US Military being the biggest user, but Europe and Australia have banned its use for all but "critical applications" such as aviation, military, and police use.
The manufacture of UL Listed halon 1211 extinguishers was supposed to cease on October, 2009. The future listing is still in discussion. Halotron I is the replacement extinguishing agent. It takes a larger volume to get the same ratings as 1211 has.
DRY CHEMICAL BEST USES: Dry Chemical "powdered" extinguishers are best used where you need to extinguish a fire, and keep it put out such as an engine fire, a cockpit fire and where the source of the fire may still be present after the fire is put out, such as a hot wire, burning embers or smoldering material still is hot and the combustible accelerator (gasoline, etc) is still present.
TYPES: The combinations of the below cover those specific hazards listed. A:B:C chemical is more corrosive than the B:C chemical version.
* "A" is for Wood and ordinary solid combustibles
* "B" is for Flammable liquids and gasses
* "C" is for Electrical equipment as energized
* "Purple K" is particularly effective for Flammable liquids and pressurized gasses
CONSTRUCTION: Beware that less expensive extinguishers without "metal heads" typically have plastic siphon tubes which may times can break off due to shock loads in the vehicle, primarily if the unit is not mounted vertically.
SIZE: A 2.5 pound extinguisher will release all of it's contents in the same time frame that a 5 pound extinguisher will, making the 5 pound more effective for larger fires which are harder to put out. Two 2.5 pound extinguishers used at the same time would be equally effective as a single 5 pounder.
SERVICE MAINTENANCE: Typically extinguishers over 6 years and under 12 years old will need to be inspected before it is recharged. This can run between $20-$25 for a 1, 2.5 or 5 pound unit. Extinguishers over 12 years old will need to be Hydro-tested before being recharged which can run $30-$35.
MOUNTING: Many extinguishers (specifically dry powder) are meant to mount vertically to reduce the chance for the internal siphon tubes from breaking off and the chemical settling to the side. Never mount extinguishers of any kind near a source of significant heat. The internal pressures inside the extinguisher can skyrocket and explode, perhaps causing far more damage and personal injury than any fire it might otherwise have put out in the future. Never mount an extinguisher under the hood. Also, mount your backup extinguisher separate from your main one. If the cockpit is under fire, one in the trunk may be the only one you can get to. Having one in the cockpit you can easily access while you are still strapped in may save your life if you are rolled over and can not get out. Practice this in advance.
HOW TO USE: Typically once using an extinguisher, you point it at the base (source) of the fire and unload all it's contents onto it even if the fire appears to be put out, is a slow, methodic back and forth sweeping motion. The additional content of a dry powder will cover and smother the fire as well as cool it and a gaseous extinguisher will keep the oxygen from the source longer to cool the source a bit more to reduce the chances of it flaring back up again. Most catastrophic fires result from when after the only available extinguisher is emptied. An afternoon at the local fire department for professional training is usually inexpensive and almost equally as important as learning first aid skills and is highly recommended.
EFFECTIVENESS: Halotron is much less effective than Halon pound for pound, although both are gaseous and both are also considered to be less effective than most dry solid powder extinguishers due to the lack of cover left behind to smother the surface of the fire source and the limited range and low wind environment the Halon and Halotron's can be used in.
CONCERNS: Halotron can remove the oxygen from your lungs (as if you lost your breath) and can be lethal in an enclosed area. Halotron is cleaner, but allows for re-ignition of the fire if the source is still present (hot surface, electrical wires, smoldering embers). Dry Chemical extinguishers are not necessarily harmful if cleaned up immediately and/or becomes wet.
DAMAGE: Fire destroys everything and anything around it. If you put out a fire and it harms the "surfaces" of some polished aluminum, big deal. It can be repolished or painted. Burned surfaces are destroyed not only cosmetically but also structurally. And a fire left to burn with destroy everything around it.
BACK-UP: Once you use the extinguisher, the fire has a good likeliness to flare back up. So a second, or even third back-up extinguisher can be crucial. smaller than 2.5 pound extinguishers rarely can extinguish all but the smallest fires and will likely barely put the fire out only to allow it to flare back up again with standing there with an empty extinguisher.
RECHARGE: Once a Halotron or Dry chemical extinguisher is used, even if just a little bit, it should always be recharged since the seal could leak down and render the unit useless when needed later. Dry Chemical particles getting in between the seal is more likely to leak down than the gaseous Halotron, but both are recommended to be recharged after any usage.
TESTING: All extinguishers should be tested annually by a qualified and certified fire extinguisher professional. This usually only costs less than $10.
HINT 1: If you need a clean, reusable gaseous extinguisher for those occasional and very MINOR carb backfires or oil on the header fires, using a Halon or Halotron extinguisher provides a quick, easy and CLEAN alternative in place of wasting your full sized main extinguisher. You can keep several of these nearby as they are small in size.
HINT 2: Keeping more than one extinguisher of different types on board can greatly improve the versatility and effectiveness of your response if you ever need to defend against a fire.
TRUNK: Keep an extinguisher in the trunk for your backup extinguisher. Make it at least a 2.5 pound but preferably a 5 pound unit if possible. Be sure to make it accessible even with a truck full of cargo and eliminate the possibility of the trunk contents from inadvertently setting off the extinguisher.
COCKPIT REAR WALL: Keep a Dry B-C extinguisher for primary unit in the cockpit. Make it a 2.5 pound unit for space. The use of either Dry and/or gas extinguisher may be debated, but having one of each and at least two total is a very, very good idea regardless of which is used where.
COCKPIT BEHIND SEATS: Keep a small disposable kitchen "D" extinguisher along both driver and passenger seats for use in minor, predictable fires to save the seals in the big units.
Remember, it may not be just you that needs the extinguisher. How would you feel if you helped a friend put out his fire and later on your car burns down because your extinguisher is empty? Keep in mind if a fire started in the first place, there IS A PROBLEM. And if there is a problem, it has a good change it will reoccur before you have time to refill a single, lone empty extinguisher.
Fire is the worst disaster anyone could experience. Never come to a shootout armed with a muzzle loader and only one bullet.
Just like any tool, understanding it's purpose, and using it correctly is crucial to the performance and results of the tool's application. And fire Extinguishers are a very commonly misunderstood tool.