2007, Piran, Slovenia

Personal protective equipment
Finally the role of pre-exercise on heat stress was experimentally studied at the Fire
Training Centre of the Amsterdam Fire Brigade. Eight professional fire fighters of the
Amsterdam Fire Brigade performed a standardized live fire ‘search-and-rescue’ task
twice over two days. Standard turn-out gear and SCBA were used. Prior to one of
both ‘search-and-rescue’ tasks the fire fighters carried out a 20 minute weight
dependent (1.5 W.kg -1 ) bicycle ergometer test to provoke an exercise induced prewarming
effect. During both testing days core temperature was recorded using an
ingestible core body temperature pill (CorTemp TM , HQ Inc., USA). Performance time
on the ‘search-and-rescue’ task was also recorded.
RESULTS
The results of the material measurements showed an increase in thermal properties of
the used clothing, especially water vapour resistance of used turn out gear (Table 1).
This is mainly caused by a deterioration of the lining of the turn-out gear.
Table 1 Results of textile material measurements
Heat
resistance
(m 2 •°C/W)
Water vapour resistance
(Pa•m 2 /W)
Air permeability
(l/m 2 •s) at 200Pa
Sleeve Front Back
Reference clothing 0.21 22.7 7.2 8.1 7.7
Used clothing 0.23 32.9 8.2 9.1 8.4
Difference (abs) 0.02 10.2 1.0 1.0 0.7
Difference (%) 9.5 44.9 13.2 11.7 8.4
However thermal physiological model calculations (THDYN) showed a marginal
effect of the deterioration on the maximal allowable working times during smoke
diving activities. The maximal predicted working time decreased from 28 minutes to
26 minutes, which is still more then the usually accepted working time of 20 minutes
(Bos et al., 2001).
The interviews pointed towards a wide variety of causes that play an important role in
the occurrence of heat stress. The causes can be divided in two categories: human and
technical. Human factors are duration and intensity of the exposure to heat,
characteristics of tasks and activities during the work, history of physical exertion,
hydration status and individual characteristics (fitness, body composition,
acclimatization and genetic predisposition). Technical factors that can be identified
are choice/assembly and state of maintenance of the turn-out gear.
The results of the experiments on the effects of pre-exercise indicate the existence of a
‘warm-up effect’ that can be attributed to non fire fighting related activities. This
‘warm-up effect’ may lead to an earlier onset of symptoms of heat stress during
common fire fighting tasks. Given this earlier onset of symptoms, an important
practical consequence may be a shortening of the maximal acceptable working time
under hot conditions. The results (table 2) showed a higher mean core temperature
during the combined bicycle ergometer test / ‘search-and-rescue’ task compared to
the single ‘search-and-rescue’ task (37.84 versus 37.59°C). The absolute highest core
temperature was also higher during the combined test (38.38 versus 38.02°C). The
197