3. Differentiate between fixed temperature and rate types of fire detector. Sketch and describe a fire detector of the rate of rise type and explain how a gradual rise of ambient temperature is accommodated.
4. With reference to fire or explosion explain the significance of the following properties of a flammable gas:
a. Combustion pressure
b. Explosive limits
c. Flash point
d. Density
5. Sketch the construction and describe the operation of the following types of fire detector:
a. Vapour product (ionisation)
b. Flame sensor (infrared)
c. Heat sensor (rate of rise)
Explain why use of all three types together is to be preferred to the use of one of these types alone.
Class 2
1. Compare with reasons the merits and demerits of the following permanent fire extinguishing systems installed in machinery spaces:
a. High-pressure water spray
b. Carbon dioxide smothering
c. Chemical foam smothering
2. Describe with sketches how the following portable fire extinguishers are operated:
a. Chemical foam
b. Carbon dioxide
Explain how they extinguish fire. State with reasons for what type of fire each is most suited for
3. Sketch and describe a self-contained breathing apparatus. Give two advantages and two disadvantages of this equipment compared to the smoke helmet. State the signal system used when wearing breathing apparatus. Describe with line diagrams a fixed carbon dioxide fire smothering system for an engine room.
4. Explain the need for an action alarm stating when and how it operates. Give a reason for gang release and explain how this is achieved.