Maximal working times with a self-contained breathing apparatus

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Abstract
The effects of a self-contained breathing apparatus (SCBA, total weight of 15·5 kg) on relative aerobic strain (%[Vdot]O2max) and heart rate (HR) were studied at light, moderate, and heavy exercise levels on a treadmill in temperate conditions. The subjects comprised 13 firemen whose mean [Vdot]O2 max was 4·161 min−1 (range 2·85 to 5·331 min−1). Maximal working times (WTmax) with SCBA were calculated with the results for this study and with experimental data from the literature. The subjects' %[Vdot]O2 max and HR increased significantly more with SCBA than in the control test without SCBA. This increase reduced the calculated WT max values. During moderately heavy exercise ([Vdot]O2control = 2·01 min−1), carrying SCBA increased the subjects' %[Vdot]O2max from 48 to 69 and decreased their estimated WT max from over 60 to 44 min. The estimated WT max for a single operation with SCBA was critically short (18 min) when the average [Vdot]O2 max for men aged 20–29 (3·51 min−1) was used in the calculations. Therefore, excessive strain in an efficient fire fighting operation of 20–30 min with SCBA can only be avoided through good physical work capacity and self-control of the physical work load.
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