Fire Triangle
Three ingredients are essential to produce a fire. They are represented on each side of the fire triangle.
1. Enough oxygen to sustain combustion
2. Enough heat to raise the material to its ignition temperature
3. Some sort of fuel or combustible material
Source of Image: Wikimedia. Fire Triangle. http://upload.wikimedia.org/wikipedia/commons/thumb/2/20/Fire_triangle.svg/330px-Fire_triangle.svg.png (accessed June 19, 2015).
Fire Tetrahedron
When a chemical chain reaction is added to the fire triangle, it becomes a fire tetrahedron. Four items are necessary to produce a fire.
1. Oxygen
2. Heat
3. Fuel or combustible material
4. A chemical reaction
Source of Image: Wikimedia. Fire Tetrahedron. https://upload.wikimedia.org/wikipedia/commons/thumb/9/99/Fire_tetrahedron.svg/220px-Fire_tetrahedron.svg.png (accessed June 19, 2015).
One of the four parts of the tetrahedron must be addressed to prevent or stop a fire.
- Keep fuel and ignition sources separate.
- Cut off oxygen to the fire by smothering.
- Use an appropriate fire extinguisher to remove part of the fire tetrahedron.
Classes of Fires
| Class | Description Potential Harm |
|---|---|
| A | Fires involving ordinary combustibles, such as wood, paper, and some plastics |
| B | Fires involving flammable liquids, such as alcohols, lamp oils, or butane |
| C | Fires involving electrical components |
| D | Fires involving metals, such as aluminum or sodium |
| K | Fires involving cooking or animal oils, such as frying foods |
Source: OSHA. Fire Protection and Prevention, 2009.
Types of Fire Extinguishers
| Class | Description |
|---|---|
| Dry chemical (multipurpose) | A, B, C |
| Water | A only (will not work for other types of fires) |
| Foam | B only (will not work for other types of fires) |
| Carbon dioxide (not to be used in confined areas) | B, C |
| Halon | B, C |
| Metal | D |
| Potassium acetate | K |
Note: In most cases, the high school laboratory will require a dry chemical extinguisher, but if you possess solid sodium or other reactive metals, a metal fire extinguisher is also recommended.
Source: OSHA. Fire Protection and Prevention, 2009.
