Warehouse BA Entry: Two Cylinders, Two Durations, One Way Out
A fire in a 20,000 m² single-storey distribution warehouse, 9 m to the ceiling, is burning in racked storage 60 m horizontally from the personnel door used as the entry control point. Two firefighters will take in a charged 45 mm hose line and hand tools. Crews wear 6.8 L water capacity cylinders: FF1's is charged to 300 bar, FF2's only to 250 bar because the compressor was short of capacity. Work of this type consumes 50 L/min for FF1 and 55 L/min for FF2. The whistle sounds at 55 bar, and the crew works to the rule that working duration is nominal duration divided by 1.5, keeping one third in reserve. Ten minutes at the seat of the fire is expected for door entry and search, and progress in smoke with a hose and tools is about 20 m per minute. The officer must decide whether to commit both, or to change the plan, before entry.
1. Calculate the nominal and working duration for each wearer and the time the task actually needs, then decide whether to commit the team as it stands.
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FF1 (300 bar): free air = 6.8 × 300 = 2,040 L. Nominal = 2,040 ÷ 50 = 40.8 min. Working = 40.8 ÷ 1.5 = 27.2 min.
FF2 (250 bar): free air = 6.8 × 250 = 1,700 L. Nominal = 1,700 ÷ 55 = 30.9 min. Working = 30.9 ÷ 1.5 = 20.6 min.
Time needed: travel 60 m at 20 m/min = 3 min in, 3 min out; plus 10 min working at the fire; plus about 1 min at the doorway to doff and report. Total ≈ 17 min, and the pair must work to the shorter duration - FF2's.
Margin: FF1 has about 10 min spare; FF2 has about 3.6 min. On a single way out, in a 20,000 m² racked warehouse where the layout is disorienting and conditions can deteriorate or the exit can be obscured by smoke, a 3.6 min margin is not defensible: one wrong turn or a snagged hose line consumes it.
Decision: do not commit on 250 bar. Swap FF2's cylinder for a full 300 bar unit before entry (equalising working duration at about 27 min and restoring roughly 10 min of margin), or cut the task to entry-only with a second team following, or postpone entry until a full cylinder is available. Also confirm the whistle reserve: 55 bar gives 374 L, only about 6.8 min at FF2's consumption, and less if he works harder.
2. Set out what the entry control officer must record and the timings that should be set before the team enters.
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The entry control officer is the team's lifeline and must work from numbers, not impressions.
Before entry, record: names and BA set numbers; cylinder pressure at the door for each wearer; time of entry; the branch/hose line number and the route; the task and the agreed turnaround point; radio call sign and channel; and the emergency team's status.
Compute and set:
- Working duration per wearer: 27.2 min (300 bar) and 20.6 min (250 bar).
- Time to exit from the furthest point: 3 min travel plus 1 min buffer = 4 min.
- Latest turnaround time from entry = working duration − exit time: about 23 min and 16.6 min respectively. Working to the shorter, the team must turn around at 16–17 min from entry, which fits a 10 min task at the seat of the fire with 6 min travel.
- Whistle check: FF2's whistle would sound around 20.6 min after entry, which is after his turnaround time - so the whistle must not be the trigger for turning around.
Also: a two-person BA emergency team staged at the door in full BA with a charged line, a radio schedule (every 5 min or at each milestone), and a written log at the entry control point. If the team has not reported by the turnaround time, the emergency team is committed.
3. FF2 argues that the whistle gives him plenty of warning and he can stay longer at the fire. Explain the purpose of the whistle and the reserve, and rule on the argument.
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What the whistle means. It sounds at 55 bar, roughly one-fifth of a full cylinder - a fixed mechanical warning, not a calculated one. For FF2 that is 6.8 × 55 = 374 L, about 6.8 min at 55 L/min - and less if he is working hard, because consumption rises with effort, cold, stress and exertion. At high work rates 55 L/min can become 70–80 L/min, cutting the whistle warning to 4–5 min.
What the reserve is for. The whistle is not a working allowance to be spent at the fire. It is the air needed to get out when something has gone wrong: a disorientation, a hose line buried under falling stock, a change of route, a casualty that has to be dragged. The 1.5 divisor in the working-duration rule exists precisely to keep that reserve untouched during the planned task.
Ruling. FF2's argument reverses the purpose of the whistle. If the team plans to still be inside when a whistle sounds, the plan is already outside the safe envelope. The team leaves on the calculated turnaround time, not on the whistle; if the whistle sounds before the team has left the risk area, that is a signal to report it and review the entry procedure, not a normal event. In this case the answer remains: change the cylinder before entry, or shorten the task.