In the January 2015 issue of FireRescue, I discussed the different types of fire extinguishers and how they work. Let’s take some time in this column to better understand the potential applications of these extinguishers at incidents because, as was previously stated, there are a number of emergencies at which hoselines are just not the right tools for the job. The right type and size of extinguisher applied at the right time on specific fires can be very effective in controlling or extinguishing that specific fire.
National Fire Protection Association (NFPA) 1901, Standard for Automotive Fire Apparatus, with the most current edition being the 2016 edition, calls for extinguishers to be provided with new apparatus:
- For pumper fire apparatus, initial attack fire apparatus, aerial fire apparatus, quint fire apparatus, and special service fire apparatus, the following extinguishers are to be provided:
- One dry chemical fire extinguisher with a minimum 80-B:C rating.
- One 2½-gallon or larger water extinguisher.
- For mobile water supply apparatus, the following extinguisher is to be provided:
- One dry chemical fire extinguisher with a minimum 3A-40B:C rating.
- For mobile foam fire apparatus, the following extinguisher is to be provided:
- One dry chemical fire extinguisher with a minimum 80-B:C rating.
When purchasing a new apparatus, if you don’t specify anything other than what 1901 requires, it is very likely that you will get a water extinguisher, a 10 pound BC-rated dry chemical extinguisher for the 80-B:C rated extinguisher, and a five-pound ABC-rated dry chemical extinguisher for the 3A-40B:C rated extinguisher. These are generally very small for most firefighting purposes. There is no requirement for a carbon dioxide or clean agent extinguisher, and those would be more expensive than the basic extinguishers. There are no requirements for extinguishers capable of handling Class D (combustible metals such as potassium, sodium, and magnesium) fires.
I won’t spend much time in this column discussing pressurized water extinguishers. They have a variety of uses and can be a very effective tool. (See “Training Minutes: The Can,” www.fireengineering.com/articles/2016/06/firefighter-training-video-can.html.) Many firefighters have had much success with water extinguishers on smaller but growing fires using good techniques.
Let’s focus on other types of incidents and what extinguishers can be used to handle these situations.
You will generally not be able to handle a well-involved vehicle fire with a handheld fire extinguisher, especially if you didn’t specify any extinguishers beyond what NFPA 1901 calls for on your apparatus. The five- or 10-pound dry chemical extinguisher will only be effective on relatively minor fires, but if you need to attack any vehicle fire with an extinguisher, I would much prefer a 15- or 20-pound unit be available for use because of the fuels, plastics, and other combustibles found in most vehicles. The dry chemical extinguisher can have some effectiveness if you have a running fuel fire; however, an extinguisher with foam or a foam hoseline will do a much better job in that situation.
A carbon dioxide extinguisher will have limited effectiveness and is best reserved for only small/minor fires involving vehicles. The big plus of using a carbon dioxide extinguisher is that there will be no mess causing collateral damage. Using a dry chemical extinguisher on a minor fire may cause more damage than the fire itself, particularly if the chemical gets into engine parts, critical electronic/control components, or sensitive computers or other electronic equipment that happens to be left in the vehicle.
Fire departments are often dispatched to various appliances on fire. Whether it is a dryer, a heating unit, or some other type of appliance, if we can keep it small and contained, there is a good chance that the building occupants may be able to remain in the property that day. While a hoseline is a good idea and a dry chemical extinguisher will likely get the job done, both can result in a lot of collateral damage. A much better option is a carbon dioxide extinguisher, which can be very effective on an appliance enclosure and will leave essentially no secondary damage. A key tactic on any appliance fire is to shut off the power and fuel (such as gas, where applicable) to the unit, which may itself extinguish the fire and should be done to secure the appliance even if the fire has been extinguished. Think about an appliance fire in your house: How would you like the fire department to respond?
Kitchen fires in residential buildings have some similar traits to appliance fires, and the tactics can be similar also. Fires normally involve stoves, ovens, or other kitchen appliances. Power and gas should be secured, and again a hoseline or dry chemical extinguisher can be very effective. But, using a hoseline or dry chemical extinguisher will also probably take that kitchen out of service for days or longer and may result in the occupants being unable to stay in the house. As for appliance fires, consider the carbon dioxide extinguisher or, if it is simply a pot on the stove, a handy lid can be quite effective.
In a commercial building, fixed kitchen suppression systems, where present, are very effective on fires involving cooking appliances. If the system is there and hasn’t activated, find the manual activation box for the suppression system and dump the system. The system should not only quell the fire but also shut down the power/gas to the cooking equipment automatically. There will also likely be a Class K extinguisher near the cooking equipment and that can be used as well. It functions somewhat differently than other extinguishers with more of a fine mist discharge, which minimizes splashing of cooking oils. If a Class K extinguisher is not available, a carbon dioxide extinguisher is a much better option than dry chemical. It will not leave residual damage (which will be throughout the kitchen), and the dry chemical can actually deteriorate the foamy extinguishing layer created by wet chemical fixed kitchen suppression systems.
Electrical fires can vary from small smoldering electrical equipment to very large transformer fires. (See “Philadelphia Firefighters Battle Electrical Substation Fire,” www.firefighternation.com/articles/2017/03/philadelphia-firefighters-battle-electrical-substation-fire.html.) Electrical fires also include computer rooms. (See the March 2017 Fire Attack column, “Protect the Data,” for techniques with dealing with these, www.firerescuemagazine.com/articles/print/volume-12/issue-4/departments/fire-attack/protect-the-data.html.)
Like appliances, getting the power shut down is the first priority, and while a dry chemical extinguisher will get the job done, the chemical agent can find its way into most other electrical equipment in the area, potentially resulting in more damage than the fire itself. This damage can result in many days of downtime for the area/building, which could be worse than the damage resulting from the fire itself. Carbon dioxide or clean agent extinguishers are a much better choice.
Water is a very bad choice in these areas for many reasons and should be avoided, but look for appropriate carbon dioxide or clean agent extinguishers in the hazard area that can be used for fires in these spaces. Unfortunately, building owners/occupants may only provide the bare minimum dry chemical extinguishers in these areas; note this during preplanning visits. Another item to look for during these visits is emergency power off buttons, which can be quickly used to shut the power down in an emergency. Gain an understanding of what they actually shut off during those visits.
Fires involving equipment generally occur in commercial or industrial occupancies. Equipment can present a wide variety of hazards including hydraulics, moving parts, compressed gases, and hazardous chemicals, among other things, as well as robots, printing presses, production equipment, and packaging lines. The tactics are much the same as with electrical fires, and carbon dioxide may provide advantages in that it creates little issue if the equipment uses most types of hazardous materials. Recently, during a response to a fire in a circuit board manufacturing facility that uses heated acid baths, the carbon dioxide extinguisher was the weapon of first choice, with a water line if needed for backup. Like electrical fires, it would be very useful if the facility located proper extinguishers in the area of the hazard and if emergency shutoff buttons were immediately available to protect the equipment and perhaps control the fire.
Fires involving chemicals are often tailor made for some type of extinguishing agent. We often teach firefighters about flammable gas fires using a “Christmas tree” type setup that emphasizes working the fire from the bottom up, with the strong caveat that any fire involving a flammable gas must have the gas supply controlled to avoid a reflash or, worse, an explosion because of leaking, unburned gas. Dry chemical extinguishers have proven to be quite effective in this situation.
|When specifying a new apparatus, give at least a little thought to the extinguishers you will carry.|
For a fire involving flammable and combustible liquids, dry chemical is again the best option for a portable extinguisher. Trained firefighters can be very effective, particularly on combustible liquid fires, with a 20-pound dry chemical extinguisher. Although a foam extinguisher can handle some liquid fires, the capability is limited to small fires, and it must blanket the entire liquid surface to be fully effective. With liquid fires, the issue of collateral damage is usually not a significant one as the heat and other combustion products from these fires already cause much damage, and these fires need the firepower of a special extinguishing agent. Be sure to shut down supply lines and liquid pumps if any flowing or pressurized liquids are involved in the incident.
Many of the tactics already described in this column for other hazards apply to laboratories as well. For more information on laboratory hazards and fires, see “Science at Its Worst” in the July 2016 issue of FireRescue, www.firerescuemagazine.com/articles/print/volume-11/issue-7/firefighting-operations/science-at-its-worst.html.
FIRES INVOLVING METALS
As discussed in the previous extinguisher articles, extinguishers designed for flammable metals are often chemical specific. Not all Class D extinguishers are good for all types of Class D fires, so it is important to have the right agent for the fire that is burning. Metal fires burn very hot, and burning metal pieces can quickly spread fire to surroundings as well as penetrate firefighting gloves and turnout gear. These fires need to be contained quickly. To be fully effective, the dry powder agent must completely cover the burning material. Pour or shovel the agent onto the burning material, and avoid pressurized application, as you may just spread the burning material. If the correct Class D extinguisher is not available, keep water away from the burning material, attempt to segregate the material from any other nearby combustibles, and allow it to burn itself out.
WHEELED UNITS/TRUCK-MOUNTED SYSTEMS
Most fire departments don’t have wheeled fire extinguishers as part of their response fleet, but some industrial facilities just might have these units in or around special hazards in their plants. Facilities such as parking garages, flammable liquid hazards, large electrical installations (if present, it will usually be a carbon dioxide agent), airports or helipads, or other unusual hazards might just have these units present, and they can be a very effective tool at a fire there. During visits to properties, be on the lookout for wheeled units that could be used at incidents at those properties.
However, some departments do operate apparatus with “twin agent” capabilities. Twin agent units have traditionally been a dry chemical agent (often “Purple K”) paired with foam firefighting capability. This combination has proven to be very effective for flammable liquid incidents, such as larger vehicles, aircraft, etc. The chemical agent is applied initially to knock down the fire, with the foam agent applied to prevent a reflash of the fire. There may be variations on this with clean suppression agents, standalone clean agent, or carbon dioxide firefighting units. Again, the chemical and foam units can create a lot of collateral damage but can get the job done. These units typically need to be on the scene of an incident quickly and make a rapid initial attack to be most effective. They are expensive to purchase and expensive to maintain and require special training for those who will operate them. Some industrial facilities have plant response vehicles set up with special agent capabilities like this.
SELECT APPROPRIATE EXTINGUISHER
In all the situations I have discussed, no matter which tactics you choose, be sure to wear self-contained breathing apparatus as the combustion products from appliances will be nasty and the extinguishing agent used also creates respiratory hazards. Full personal protective equipment is also called for, as you may need to move the appliance/pan, etc., and parts will be hot, and the potential for a fire to flash is always present.
There is a time and a place for fire extinguishers vs. hoselines, and you must be familiar with all the weapons you have at your disposal to be good at your craft. When specifying a new apparatus, give at least a little thought to the extinguishers you will carry and go above and beyond what NFPA 1901 calls for. My recommendation is at least one “water can,” a 15- to 20-pound ABC dry chemical extinguisher, a 15- to 20-pound carbon dioxide extinguisher (a larger size clean agent extinguisher may be substituted in lieu of both the dry chemical and carbon dioxide extinguisher, although they can be costly), and an extinguisher effective on metal fires if you could run into those hazards in your response area.
Quite often, you can find appropriate extinguishers in the immediate area of the incident or hazard that you are responding to. Look around the incident site and see if there is an appropriate extinguisher that you can use to handle the emergency. Remember, however, that the least expensive extinguishers are typically water and dry chemical extinguishers. They meet code requirements for extinguishers in a building and may be what is found in the area, even though they may not be the best extinguisher for the job. I would never tell you not to have an attack line handy on any type of working fire, but understanding the potential applications of the various extinguishers, as well as knowing what extinguishers are located in the area of specific hazards, may just keep a small incident small and damage to a minimum.