|
  In order to
prevent the effects arising from thermic stress due to failure of the
thermoregulation mechanisms, microclimatic indices of stress have been
devised in order to point out the existence of thermic stress risk as a
result of metabolic situations or excessive physical strain. An example
of such indices is represented by the WBGT (Wet Bulb Globe Thermometer):
depending on its value, the job can be carried out continuously (heavy,
medium and light jobs) or, on the other hand, with compulsory hourly intervals.
As a result of the general improvement of the microclimatic conditions in
the working environment and of the adoption, in many working sites, of
air conditioning systems, more complex indices have been developed in
order to verify the existence of subjective conditions of thermic
wellbeing. Among the so-called thermic comfort (mental condition of
satisfaction in relation to the thermic environment) indices, the most
used is the PMV (Predicte Mean Vote) of Fanger. The PMV index is based on
the new elaboration of the equation of thermic balance, taking into
account the combination of:
(i) air temperature
(ii) average radiant temperature
(iii) air speed
(iv) vapour pressure of the air
(v) measured energetic expenditure
(vi) thermic resistance of clothing (in Clo)
The index predicts the subjective thermic sensation on a scale with 7
steps (ranging from +3 very hot to -3 very cold) as expressed by subjects
exposed to the same microclimatic conditions. The ISO/DP regulation 7730
recommends PMV values between +0.5 and -0.5 to maintain thermic comfort.
Thermic stress prevention is carried out by acting on the different
components of the thermic balance equation both by reducing the
production of endogenous heat and by increasing the heat produced. In the
first case it is possible to act on the characteristics of the operative
task, in the second case on the environmental parameters.
On the wards, advisable air temperature should range from 20°C to 24°C
during the winter and from 22°C to 26°C in the summer, with relative
humidity values included in a wide range (35-70%) and air speed less than
0.2-0.3 m/sec. As far as the so-called care wards (such as operating
theatres) are concerned, air temperature and humidity values should be
sensibly higher (humidity values around 50-60%). As far as offices are
concerned, air temperature values should range between 20°C and 24°C and
humidity values between 40 and 70%, with air speed around 0.1 m/sec.
|
![[Rischi lavorativi in ambiente sanitario]](ico/sottotitolo.gif){kind=small}
![[collegamenti]](ico/collEpre.gif){kind=small}
