Gas technicians/fitters are often exposed to hazardous materials that are flammable or potentially explosive. This module will help you understand fire prevention, detection, and response.
Fire is the rapid oxidation of a flammable material in the chemical process of combustion, releasing heat, light, and various reaction products. Oxidation takes place at varying rates, from very slow processes like rusting iron to extremely fast reactions like exploding gunpowder.
The combustion triangle illustrates the three elements needed for fire:
The advanced combustion tetrahedron adds a fourth element: the uninhibited chemical reaction. This model provides a more complete understanding of fire behavior.
| Rate of Oxidation | Example |
|---|---|
| Very slow | Rusting iron (not fire) |
| Slow | Spontaneous heating of materials (oil-soaked rags) |
| Fast | Burning paper or wood |
| Extremely fast | Exploding gunpowder |
What are the three elements of the fire triangle?
Fires are divided into main types or classes, which dictate the type of extinguisher required to fight them. Fires are rated by type: A, B, C, D, and K. These designations are also used to rate fire extinguishers.
Symbol: Green triangle with "A"
Materials: Ordinary combustibles such as wood, cloth, paper, rubber, and many plastics
Characteristic: These materials leave ash when they burn
Extinguishing Agent: Water or dry formula agents that use heat-absorbing (cooling) effects
Symbol: Red square with "B"
Materials: Flammable liquids such as gasoline, oil, grease, tar, oil-based paint, lacquer, and flammable gases
Extinguishing Agent: Agents that prevent vapor release or interrupt combustion via oxygen depletion
Symbol: Blue circle with "C"
Materials: Energized electrical equipment such as wiring, circuit breakers, machinery, or appliances
Danger: Risk of electrical shock
Extinguishing Agent: Non-conductive agents to protect the operator
Symbol: Yellow star with "D"
Materials: Certain combustible metals such as magnesium, titanium, zirconium, sodium, or potassium
Extinguishing Agent: Dry powder that absorbs heat and smothers flames, cutting off oxygen
Symbol: Black hexagon with "K"
Materials: Vegetable oils, animal oils, or fats in cooking appliances
Environment: Commercial kitchens
Extinguishing Agent: Wet chemical that forms a foam blanket to smother the fire
Which class of fire involves energized electrical equipment?
Materials that can easily catch fire should be kept away from any open flames.
Undetected gas leaks can lead to dangerous accumulations of flammable gas.
LP-gas storage cylinders near oxygen cylinders, electrical circuits, welding tools, or flammable liquids.
Broken or improperly installed venting systems can lead to gas buildup.
Improper transportation or handling of gas cylinders can lead to leaks or damage.
Storage of gas cylinders in indoor, badly ventilated locations increases fire risk.
What is a major hazard when welding against wood or in dusty areas?
Fire extinguishers are a gas technician/fitter's main firefighting tools. It is critical that gas technicians/fitters know the location and method of operating each extinguisher in their workplace.
Effective on Class A fires (ordinary combustibles)
Some types effective on multiple fire classes
Effective on Class B and C fires
Specifically for flammable metals
For cooking oils and fats in commercial kitchens
Effective on multiple fire classes
The nameplates of fire extinguishers designate, by means of a rating code, the types of fires for which you can use each extinguisher. Underwriters' Laboratories of Canada (ULC) ratings show the relative hazard, coverage, and travel distance specifications.
Class D Extinguishers: The type needed depends on the flammable metals present:
Class K Extinguishers: Rated for kitchen fires involving cooking oils and deep fryers. Example: A 2A:K rating contains the equivalent to 2.5 gallons of water and is approved for cooking oil fires.
Which type of extinguisher should be used on energized electrical equipment?
Fire prevention is based on removing one or more elements of the fire triangle/tetrahedron:
Shutting off the valve of the gas main is an example of fuel starvation.
Applying suppressant or water to the fire for cooling.
Covering the fire with a lid, wet blanket, or sand, or use carbon dioxide, foam, or dry chemical.
Using a flashback arrestor to interrupt the combustion process.
What is the correct order of steps when responding to a gas leak?
Specialized garments designed to resist ignition and provide protection from heat and flames. These include coveralls, jackets, and pants made from materials that self-extinguish when removed from a fire source.
Safety goggles and face shields that protect against sparks, flying debris, and radiant heat. These should be rated for high-temperature environments.
Heat-resistant gloves that allow for dexterity while providing protection from burns and hot surfaces.
What is first-aid firefighting?
Gas technicians/fitters must maintain comprehensive knowledge of fire safety practices to protect themselves, their colleagues, and property. By understanding fire behavior, recognizing hazards, and knowing how to respond appropriately, technicians can prevent fires from occurring and minimize damage when they do occur.