A workshop is divided into three zones. The fire‑hazard rating (FHR) for a zone is calculated by $FHR = \dfrac{P \times Q}{R}$, where $P$ is the probability factor (1-5), $Q$ the quantity factor (1-5) and $R$ the control factor (1-5).

Zone A: $P=3,\; Q=2,\; R=4$.
Zone B: $P=4,\; Q=3,\; R=2$.
Zone C: $P=2,\; Q=4,\; R=5$.

Each zone must have at least one fire extinguisher. Extinguishers are classified as:
- Class A (for metal fires) reduces the zone's FHR by 1.5,
- Class B (for flammable liquids) reduces the zone's FHR by 2,
- Class C (for electrical fires) reduces the zone's FHR by 1.

The workshop requirement is that the resulting FHR in every zone must not exceed 3. Determine the minimum number and types of extinguishers required for each zone to satisfy this requirement.

Question

A workshop is divided into three zones. The fire‑hazard rating (FHR) for a zone is calculated by $FHR = \dfrac{P \times Q}{R}$, where $P$ is the probability factor (1-5), $Q$ the quantity factor (1-5) and $R$ the control factor (1-5).

Zone A: $P=3,\; Q=2,\; R=4$.
Zone B: $P=4,\; Q=3,\; R=2$.
Zone C: $P=2,\; Q=4,\; R=5$.

Each zone must have at least one fire extinguisher. Extinguishers are classified as:
- Class A (for metal fires) reduces the zone's FHR by 1.5,
- Class B (for flammable liquids) reduces the zone's FHR by 2,
- Class C (for electrical fires) reduces the zone's FHR by 1.

The workshop requirement is that the resulting FHR in every zone must not exceed 3. Determine the minimum number and types of extinguishers required for each zone to satisfy this requirement.

Accepted Answer

Zone A: 1 Class A extinguisher; Zone B: 2 extinguishers (1 Class B and 1 Class A); Zone C: 1 Class C extinguisher

City Guilds Model Questions Vol1 2017 Engineering Question 13

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