2007, Piran, Slovenia

Occupational Thermal Problems
recommended maximum time of exposure with available or selected clothing. It can be
calculated for both levels of strain from:
Q
DLE =
lim
(3) S = M − W − Eres
− Cres
− E − R − C (4)
S
where Qlim and S are the body limit heat loss and the rate of change in heat content [W/m 2 ].
RESULTS
The present survey was realised in 8 out of 18 provinces of Portugal main land. The sample
gathered consists of 32 industrial units and a total of 101 workplaces, embracing freezing and
refrigerating chambers and ambient/controlled air temperature workplaces. The measurements
were carried out according to ISO 7726 (1998) using equipment from Testo, namely the data
loggers 175-T2, 175-H2 and 445. The activity level, M, was estimated according to ISO 8996
(1990), using the methods of level II of accuracy. The standard procedure consisted on adding
the metabolic rates corresponding to the posture, the type of work, the body motion related to
the work speed and the basal metabolic rate, for each single activity. Whenever we got
authorization from the workers, the metabolic rate estimation was based on heart rate
measurements. The thermal insulation of the ensemble, Icl, was calculated following ISO 9920
(1995) by adding the values corresponding to each garment. For this purpose a questionnaire
with a set of figures representing different types of garments was used and the workers were
asked to identify the garments worn. To illustrate the measurements of the physical
parameters, Figure 1 shows the results of ta in each workplace.
ta [ºC ]
25
20
15
10
5
0
-5
-10
-15
-20
-25
Milk food industrtry
Workplace
Freezing chambers Refrigerating chambers Ambient temperature
Fish industry Meat industry Food conservation industrial units Food distribution industrial units Pharmaceutical ind. units
Figure 1. Air temperature results.
In Figure 1 three types of workplaces can be identified and associated with different
environmental conditions. The freezing chambers show air temperatures between -15 and -
25ºC. Refrigerating stores are characterised by a temperature range from 0-10ºC, and the
workplaces with ambient or controlled air temperature by ta values between 10-25ºC.
Figure 2 shows the resultant clothing insulation (Iclr) and the required clothing insulation in
terms of the neutral (IREQneutral) and minimal (IREQmin) levels for all workplaces under
analysis. It clearly shows that the ensembles commonly used are inadequate. The freezing
chambers represent the most severe case since all the workplaces reveal situations with
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