2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
502
Rectal temperature ( o C)
39.5
39.0
38.5
38.0
37.5
37.0
36.5
HT1b HT2b HT2c HT2d HT4b
'Satisfactory'
-30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120
Time (minutes)
Figure 2: Rectal temperature during the Heat Tests in Phase-B
Data presented as the 10-minute mean and 1 SD. Open squares denote HT1b (n=10); open
diamonds, HT2b (n=11); crosses, HT2c (n=10); dashed line, HT2d (n=9); and open circles, HT4b
(n=6).
Based on the findings from both phases of the study, the table below details the proposed
WBGT limits and exposure durations for each of the work rate categories, and the limits
currently used in the British Armed Forces (JSP 539, 2003).
Table 1: In-Service and proposed WBGT and exposure limits
Applicable to men not acclimatised to heat, wearing lightweight clothing. Bold type represents proposed increased limits.
Work rate
category
In-Service
WBGT limits
(°C)
In-Service
Exposure durations
(minutes)
Proposed
WBGT limits
(°C)
Proposed
Exposure durations
(minutes)
Low 32 60 34 120
Medium 26 60 32 120
High 24 60 25 120
Very high 20 60 20 120
Extreme 20 30 20 45
DISCUSSION
Empirically-based WBGT limits for male British Armed Forces personnel not acclimatised to
heat, have been proposed. Supporting previous anecdotal reports and heat strain predictions,
they indicate that the in-Service WBGT limits are likely to be ‘overly cautious’ at the lower