Fire suppression

Question 1

List the types of fires (Classes)

Answer 1

Class A: ordinary combustibles
Class B: flammable liquids
Class C: flammable gases
Class D: flammable metals
Class E: energised electrical equipment
Class F: cooking fat fires

Question 2

What are the common agents used in suppression systems?

Answer 2

Water, foam, gases, powder

Question 3

Explain how water works as a suppression agent

Answer 3

Very effective extinguishing medium but can cause damage. Effectiveness depends on the size of the drops
- Small = cools flame - high SA, same volume
- Large = gets to the base - higher weight and velocity

Question 4

Explain how foam works as a suppression agent

Answer 4

Mix of water, foam agent, air. High expansion = fill entire compartment. Medium expansion = slightly less range, creates layers to avoid reignition. Low expansion = high momentum, long distance - not suitable for compartment

Question 5

Explain how gases work as a suppression agent

Answer 5

Gases remove the heat but effect visibility. CO2 - poisonous above 30%, Inert gases - low oxygen concentration, fluorinated hydrocarbon (HFC) - dissolves to HF during fire (acidic inhalation)

Question 6

Explain how powder work as a suppression agent

Answer 6

Solid powder heats up, changes phase, breaks down. Reignition inhibition - phosphate to phosphoric acid. Smaller particles = better cooling

Question 7

What is REMP? Is lower or higher REMP good?

Answer 7

Required extinguishing media portion. Lower is better, more cost effective, less mass of media per unit mass of fuel.