Foam

Question 1

State the application rate of foam:

Answer 1

6.5 litres per minute per m2 (in a contained or bunded area)

Example:

1. The fire area is estimated to be 10m x 20m = 200m²
2. 200m² x 6.5L/min/m² = 1300l/min is required over the area
3. 1300L/min x 10min = 13,000L of foam solution is required over 10mins of application

Question 2

What are five (5) advantages of foam:

Answer 2

• Foam requires less water to extinguish a fire.
• Foam reduces the danger of re-ignition due to smothering and insulating effects.
• Foam can be used to totally flood areas or compartments.
• When used on shipboard fires, its lightness reduces the stability problems created by large volumes of water.
• It can be used to extinguish fires where firefighters are unable to access the fire or to use water streams.

Question 3

What are four (4) disadvantages of foam:

Answer 3

• The correct foam proportioning equipment is essential to produce the optimum quality and quantity of foam
• Foam concentrate can be quite expensive
• Foam may be attacked by certain chemical agents
• The foam application may be affected by strong winds which can expose the fuel and allow re-ignition to occur. Winds can also prevent the stream reaching the fire.

Question 4

What are the three (3) mixing components to create foam?

Answer 4

• Foam concentrate
• Water
• Air

Question 5

State the expansion ratios of the following foam applications:

• Non - aspirated foam
• Low expansion foam
• Medium expansion foam
• High expansion foam

Answer 5

Non - aspirated foam/aspirated:

expansion ration = 4:1

Low expansion foam:

Expansion ratio ranging between 2:1 to 20:1, but usually between 5:1 to 15:1

Medium expansion foam:

Expansion ratio ranging between 20:1 to 200:1, but usually between 50:1 to 150:1

High expansion foam:

Expansion ratio ranging between 200:1 to 2000:1, but usually no more than 1200:1

Question 6

What are the safety considerations when working in a space totally filled with high expansion foam:

Answer 6

• Breathing Apparatus must be worn
• Toxic gases (e.g carbon monoxide, domestic gas etc.) may be trapped in high expansion foam, visibility is nil and hearing is impaired.
• Guidelines must be used and strict supervision maintained over persons entering foam

Conductivity:

• High expansion foam is a weak conductor of electricity. An awareness of the dangers of electrical wiring and machinery either partially or totally submerged must be maintained.