Maximal working times with a self-contained breathing apparatus

The effects of a self-contained breathing apparatus (SCBA, total weight of 15·5 kg) on relative aerobic strain (%VdotO2max) 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 VdotO2 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' %VdotO2 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 (VdotO2control = 2·01 min−1), carrying SCBA increased the subjects' %VdotO2max 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 VdotO2 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.