FIRE EXTIGUISHERS

FIRE EXTIGUISHERS, AT THE TOP OF ROOFING SAFETY

Since my last blog was on the subject of fires, I thought it might be a good time to add a blog on fire extinguishers, as we use them in the roofing industry. It is also good information for the homeowner to use when selecting the proper fire extinguisher for home use.

As the Safety Manger for several roofing companies, I visit job sites and the various shops and offices and do safety inspections. One of the most important things I look for is the presence of fire extinguishers. Though fires are not considered to be a major threat, we do work with flames and other heat sources as tools that have the potential to ignite and we work with numerous materials that may be good fuels for fires. A fire at the job site or at the shop and offices could be extremely costly.

On the job site, we require at least one fire extinguisher on the roof and, if hot asphalt kettles are employed, at least one on the ground for use by the kettle operator. Every work vehicle is also required to have a fire extinguisher. In the shops, we require fire extinguishers in the mechanic’s garage, within easy access in the material storage bays, and within easy access in our offices. As Mark T. Conroy points out in his chapter of the Fire Protection Handbook, “Fire Extinguisher Use and Maintenance,” the choice of an extinguisher “depends on the nature of the fuels present, who will be using the extinguisher, and the environment.”

Fires are divided into 4 types or classes for extinguishing purposes; A, B C, and D. Because of the nature of a particular type of fire, a particular type of extinguishing agent is required to suppress it effectively and safely. Class-A-rated fire extinguishers are designed to extinguish ordinary fires fueled by wood and other cellulosic materials. They typically use water, loaded stream, aqueous film-forming foam (AFFF), or film-foaming fluoroprotein foam (FFFP) as extinguishing agents, but can also use dry chemicals or halogen.

Class B fires are fueled by flammable liquids and are extinguished by extinguishers using carbon dioxide, dry chemicals, FFFP, AFFF, and Halogen agents. Portable B-class-extinguishers, however, are only effective on relatively small flammable liquid fires because of the intense heat and smoke generated by larger fires of 10 square feet or more.

Class-C-rated fire extinguishers are employed for electrically generated fires. Class C agents include carbon dioxide, dry chemicals, or halogen. Be cause of the potential of electrical shock or electrocution, water and aqueous foams are not used as class C agents.

Class-D-rated fire extinguishers are used to extinguish fires fueled by combustible metals. Special dry powder is used to extinguish class D fires.

It is important that the potential user of a portable fire extinguisher be competent in its use. The users should be trained in their use. Many portable extinguishers will spend its entire agent within 8 to 15 seconds, so accuracy is needed. Experimentation is not an option in a crisis situation.

Most fires are extinguished by cooling and/or smothering. For example, “water is effective as a cooling agent because of its high latent heat of evaporation…When the heat loss exceeds the fire heat gain, the fuel surface will begin to cool until the flame can no longer exist at the surface” Water also has the capacity to emulsify and dilute fire fuels.

Carbon dioxide is not as good an agent for cooling a fire as water, but it is effective in smothering it. Carbon dioxide replaces the oxygen in the atmosphere that the fire needs to sustain itself. However, carbon dioxide has little effect on fuels such as cellulose nitrate, which contains its own oxygen supply. Another draw back with carbon dioxide is the fact that in a small, unventilated area, the oxygen supply of the extinguisher user is also depleted.

Dry chemicals provide both cooling and smother elements for fire extinguishment but also add an extra dimension. “When introduced directly to the fire area,” writes David R. Hague, “dry chemicals cause extinguishment almost at once. Smothering, cooling, and radiation shielding contribute to the extinguishing efficiency of dry chemical, but studies suggest that a chain-breaking reaction in the flame is the principal cause of extinguishment.”

In the roofing business, we use only dry chemical fire extinguishers with an ABC-class-rating, the most practical type since the potential fuels on the job site are many. We use hot asphalt, asphalt-saturated rolled materials, modified bitumen materials, rubber roofing, flammable glues and cleaning solutions, gasoline, propane, and wood fiber and foam insulations. D class fires are extremely unlikely in the roofing industry.

Inspection, maintenance, and practical location of fire extinguishers are necessary for fire safety. We inspect our extinguishers regularly—I check to see that all are charged and in place as part of my safety inspections—and send them out for maintenance and to be recharged as they are used—if the extinguishers are used in the field, the vehicle units are used as backups—so we always have fire extinguishers in working order. We also use dry powder from a bucket as a backup for hot-kettle operations.

In the shops and offices, we also use ABC class extinguishers, and we station our fire extinguishers in locations where they are easy to reach, within 75 feet of any place on the premises. We store the same materials in the warehouse and shop that we use in the field, and though the variety of potential fuels for fire is much less in the office environment, for the sake practicality we use the same ABC class extinguishers.

Though fire has not been a historically serious problem for us in our roofing businesses, it remains potential hazard that must not be ignored. So, as long as I am the safety manager, we will continue to be prepared. We will understand the volatile nature of the materials we use, control our environment, and make sure that we have the appropriate and maintained fire extinguishers for the job and the trained personnel to abate the potential hazards.

Sources

Convoy, Mark T., “Fire Extinguisher Use and Maintenance,” Fire Protection
Handbook 18th ed., Quincy, Massachusetts, National Fire Protection Association.
1997.
Hague, David R., “Dry Chemical Agents and Application Systems,” Fire Protection
Handbook 18th ed., Quincy, Massachusetts, National Fire Protection Association.
1997.
Petersen, Marshall E., “The Role of Extinguishers in Fire Protection,” Fire Protection
Handbook 18th ed., Quincy, Massachusetts, National Fire Protection Association.
1997.
Wahl, Andrew, M., “Water and Water Additives for Fire Fighting,” Fire Protection
Handbook 18th ed., Quincy, Massachusetts, National Fire Protection Association.
1997.
Wysocki, Thomas J., “Carbon Dioxide and Application Systems,” Fire Protection
Handbook 18th ed., Quincy, Massachusetts, National Fire Protection Association.
1997.