Title: 
Headings:  HEAT STRESS AND HEAT STRAIN
HEAT
 
STRESS
 
AND
 
HEAT
 
STRAIN
 

.'tfd-®A11
 


Content: Acclimatization
 
is
 
a
 
gradual
 
physiological
 
adaptation
 
that
 
improves
 
an
 
indi
vidual's
 
ability
 
to
 
tolerate
 
heat
 
stress. Acclimatization
 
requires
 
physical
 
activity
 
under
 
heat-stress
 
conditions
 
similar
 
to
 
those
 
anticipated
 
for
 
the
 
work. With
 
a
 
recent
 
history
 
of
 
heat-stress
 
exposures
 
of
 
at
 
least
 
two
 
continuous
 
hours
 
(e.g.,
 
5
 
of
 
the
 
last
 
7
 
days
 
to
 
1
0
 
 
of
 
14
 
days),
 
a
 
worker
 
can
 
be
 
considered
 
acclimatized
 
for
 
the
 
purposes
 
of
 
the
 
TLV®. Its
 
loss
 
begins
 
when
 
the
 
activity
 
under
 
those
 
heat
 
stress
 
conditions
 
is
 
discontinued,
 
and
 
a
 
noticeable
 
loss
 
occurs
 
after
 
four
 
days
 
and
 
rT)ay
 
be
 
completely
 
lost
 
in
 
three
 
to
 
four
 
weeks. Because
 
acclimatiza
tion
 
is
 
to
 
the
 
level
 
of
 
the
 
heat
 
stress
 
exposure,
 
a
 
person
 
will
 
not
 
be
 
fully
 
accli
matized
 
to
 
a
 
sudden
 
higher
 
level; such
 
as
 
during
 
a
 
heat
 
wave. The
 
decision
 
process
 
illustrated
 
in
 
Figure
 
1
,
 
 
should
 
be
 
started
 
if
 
(
1)
 
 
a
 
quali
tative
 
exposure
 
assessment
 
indicates
 
the
 
possibility
 
of
 
heat
 
stress,
 
(2)
 
there
 
are
 
reports
 
of
 
discomfort
 
due
 
to
 
heat
 
stress,
 
or
 
(3)
 
professional
 
judgment
 
indi
cates
 
heat
 
stress
 
conditions. Section
 
1: Clothing. Ideally,
 
free
 
movement
 
of
 
cool,
 
dry
 
air
 
over
 
the
 
skin's
 
surface
 
maximizes
 
heat
 
removal
 
by
 
both
 
evaporation
 
and
 
convection.