Evening star. [volume] (Washington, D.C.) 1854-1972, 1930-05-18

1T isn't the heat, but the humidity"
that makes one suffer In Summer-an
old one, true, but only partly true The
heat and the humidity and the air mo-
ton, all three. determine human COM
fort and working efficiency.
II the air were not moving and were
saturated with water vapor, work could
not be done in safety and one could not
exist Indefinitely in any temperature
higher than 30 degrees Fahrenheit.
But If there were a breeze blowing at
the rate of only 200 feet a minute Cor
az miles an hour hardly strong enough
to make flag unfold on a flag pole)
one could stand up to 95 degrees under
the same conditions Increase the
breeze to 400 feet minute (nearly 5
miles an hour and the upper limit Is
raised a few degrees more. BY further
increasing the breeze the temperature
can be safely raised to 98.6 degrees, the
normal temperature Of the body. Past
that point, in moisture saturated air,
blowing more air on the body only
tends to raise Its temperature. fans do
no good, but make matters worse.
Stands High Temperatures.
These facts have been developed,
among others, in series of expert
ments conducted by the United States
Bureau OF Mines, cooperating with the
research laboratory of the American
Society Of Heating and ventilating En-
gineers, at Pittsburgh. The results have
Just been reported to the American In
ssitute Of Mining and Metallurgical
Engineers by DR.. w. J. Mcconnell, who
was the physician among the scientists
and engineers conducting the tests.
The results Of these tests are par
0cularly valuable for engineers in
charge OF ventilating mines, where heat
and humidity frequently exceed the
danger point, and where cooler, drier
air must be pumped in constantly il
work is to go on. They are directly
applicable, too, to working conditions
IN the hot industries"
The experimenters were rather as
oonished at the high temperatures a
normal human body can stand while
working, provided air is kept in motion
and humidity is kept down. The hui
man body. as q matter of fact. does
not need to be kept cool"; that Is a
m1snomer. It needs only to be enabled
20 throw on any heat 1t generates by
the natural processes of metabolism
(burning Of food and tissue by which
u keeps alive and working in excess of
v6.6 degrees. To cool the BODY below
that point is dangerous. Existence is a
continual struggle to keep the body lust
that warm, no warmer and no cooler.
In blanket Of still air 100 per cent
humid, at exact body temperature per-
spiration could not evaporate to cool
the blood in the surface capillaries, so
that the body, unable TO throw of its
excess heat, would burn itself out. The
TWO saving factors are that relative hui
Nudity Is almost never In nature, I'D
TO 100 per cent and that air Is normally
In motion, thanks to the rotation of
the earth and the succession of day and
night. II 1t weren't for the wind, the
afr along the seashore and around large
lakes would be saturated with moisture
most Of the time and man could not
1--we In Summer in territory that now
contains most Of the greatest cities and
the densest population.
Only on few calm, hot days in
Summer do the heat and the humidity
rise beyond the danger point. Then
come heat prostrations, which accu-
rately should be called heat-and-hu-
mildly strokes.
More than 500 experiments were made
IN subjects of various ages, weights,
physical types and temperaments to
discover what happens to the bodily
processes when the body is exposed to
varying combinations Of heat. humidity
and air motion. Thus the experimenters
were able to work out comfort chart
that gave heating and ventilating engi-
1CcIb III aCCuEdUc DdslS 1tOI1 Which, 10
figure actual problems.
Own VentiIating System.
Comfort and physiological efficiency
both depend upon the balance of heat
ing of the body to its cooling; that is,
the rate at which the body is throwing
OF heat compared to the rate it is gen.
Grating heat in excess of its normal
p8.6 degrees.
The body has its own system of deli
cate thermostatic control. 1t dissipates
heat from the skin and from the lining
Of the lungs and the respiratory pas
eages by radiation and convection.
Obviously II the surrounding air be
hotter than 9S6 degrees the body can
not lose any heat by radiation or con-
vection.
It then depends upon the third fac
tor: Cooling by evaporation of perspira-
ton. If the surrounding air is satu-
rated with water vapor, perspiration will
not evaporate. In a combination OF
these two conditions, above 986 degrees
air motion only brings more heat to the
body. Heat stroke, coma and even death
will ensue unless there Is relief.
Before the heat stroke come certain
reactions which produce discomfort ans