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 (% .ovrhdot.VO2 max) 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 .ovrhdot.VO2 max was 4.161 min-1 (range 2.85 to 5.331 min-1). Maximal working times (WT max) with SCBA were calculated with the results for this study and with experimental data from the literature. The subjects'' % .ovrhdot.VO2 max and HR increased significantly more SCBA than in the control test without SCBA. This increase reduced the calculated WT max values. During moderately heavy exercise (.ovrhdot.VO2 control = 2.01 min-1), carrying SCBA increased the subjects'' % .ovrhdot.VO2 max 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 .ovrhdot.VO2 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.