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Sitting an hour in still, saturated air at 100° F. (Table III A) caused symptoms similar to those found at lower temperatures, but they appeared earlier. Each subject quickly had definite increase of body temperature and pulse rate, subjects Nos. 2 and 5 having & maximum body temperature of 102.3o, subject No. 1 of 103.3°, and subject No. 4 of 103.8°. Subject No. 2 had a maximum pulse rate of 152, subject No. 5 of 168, and subject No. 4 of more than 175.

All perspired very profusely (even the shoes being partly filled with perspiration) and were definitely weak and dizzy upon leaving the place of the test. The symptoms persisted for about an hour afterwards. This was a very trying test for all.

TABLE III A.-Effects of resting one hour in still air at 100° wet bulb, 100° dry bulb (100 per cent relative humidity).

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8. Dry bulb.

Barometer.

Relative humidity

(per cent).

Body temperature.

Gas analysis.

Body temperature.

Body temperature.

Velocity.

Diastolic.

Systolic.

Body temperature.

Pulse.

Diastolic.

Systolic.

Pulse.

Systolic.

Diastolic.

Pulse.

Feet.

At 2,700 level in drift.

a. m. 8.50

26.58

89

201

99.8 128

81

99.6

90 118

78

99.5 130 106

9.30 100 100

74 98.8 104 Nos.2 and 5 sweating just a little; Nos. 1 and 4

sweating profusely. Had taken no exercise
except walking about 50 fect on the level. An
Italian who had pushed a car a few hundred
feer in this air for two months said he was
fusely and looked thin; his skin felt hot.
about ready to quit; he was sweating pro-
Ancther Italian was not even sweating; was

apparently unaliccted.
100.0 All were sweating, very profusely, but seemed

to be feeling well as yet. Entered this place
at 9.15, Skin of fingers shriveled at 9.40.' No.

1 had chilly sensations on back at 9.40.
101.2 166

102. 2.
68 102.3 168 At this time all felt fit; were somewhat dizzy,

but did not feel, in general, as badly as when
leaving the hot location.

26. 58! 100

10

100. 31

100.2

In 2,706 level, drip

pers falling froin roof. .

100.6

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EFFECT WITH AIR NOVEMENT.

In the moving air at 91° and 98 per cent relative humidity (no tests being made on subject No. 5 at this temperature in still air). Figure 1 shows that the body temperature of subject No. 5 increased very little by sitting still for an hour, but that it was definitely increased in moving, saturated air 95°, more seriously affected by moving, saturated air 96}', and still more so by saturated air at 981° temperature. Subject No. 5 (as well as the other subjects) was unable to endure for the full hour the moving, saturated air at 100°, and the graph shows that this air, though endured less than the usual hour, ran his body temperature 3.1 degrees above that at the beginning of the test, or to above 102° F.

As was the case in the still air, the effect of the moving air on the pulse of subject No. 5 was similar to the effect of the moving air on his temperature, except that in the 95° moving air his pulse did not rise as did his temperature, but fell slightly instead. This was probably due to the fact that his pulse was high at the beginning of this experiment on account of exertion in helping set the fan; otherwise it is probable that his pulse rate would have remained practically the same throughout this test. There was an increase, from the initial rate, of 12 beats in the 917° moving air, of 20 beats in the 964° moving air, of 38 beats in the 100° moving air (in 49 minutes, as he could not remain the full hour), and 40 beats in the 987° moving air.

Table I.-Effects of resting one hour in moving air at 911° wet bulb, 911° dry bulb (98 per cent relative humidity).

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98.8 112 104 781 98.8 112 All were sweating very freely, although they

had done nothing but walk 1,200 feet along a level drift in air moving about 30 to 50 feet

per minute.
(All resting in moving air and felt very much

cooler. The inucker, who was working in
this place, said that without the fan he could
stand it for about 15 minutes, then had to go
down to air for about the same length of time;
but he said that with fan he could stand it

all day.
99.5

99.0 By 10.15 the hands and arms of all subjects were

îrce of sweat and they were sweating only a

little at forehead and face. 100.0

99.0 The workmen went up into the stope at noon

to eat where the fan was operating. The
shift boss said the men would do twice as

much work with the fan as without it.
100.0 98 66 99.1 124 Just before readings, No. 2 had walked 3,500

feet on level in air about 90° saturated. Nos.
1, 4, and 5 had walked 1,200 feet just before
readings.

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Al subjects felt well throughout the more than one hour spent in the moving, practically saturated air at 911° F. (Table 1); there was no headache or dizziness and comparatively little perspiration. However, when the fan that produced the air movement was stopped, the place became oppressive immediately and perspiration quickly became profuse. The place in which this test was made was a stope just above a level 2,700 feet from the surface. The air was not quite saturated (911° wet bulb and 911° dry bulb), but it was absolutely stagnant and so oppressive that the workers were accustomed to go to the level below to cool after having worked in the stope for about 15 or 20 minutes, returning to work after a rest of 15 to 30 minutes. A small compressed-air-driven fan, consuming about 20 cubic feet of air per minute, was introduced by the investigators to give local movement to about 5,000 cubic feet of air per minute from the place, merely recirculating the air essentially as is done by the ordinary office fan, the velocity being over 3,000 linear feet per minute at the fan, diminishing to a few hundred feet per minute at a point 25 or 30 feet distant from the fan. Whilo the noise made by the fan was somewhat annoying, the decided improvement made by moving the air was apparent immediately. So definite was this improvement after the placing of the fan that not only did the stope workers discontinue the practice of going down to the level to cool, remaining at work in the stope practically continuously, but other workers in the more or less immediate locality, who were accustomed to congregate in the level below to eat or to cool, soon began to come into the stope, as the conditions in the stope when the fan was in operation were more comfortable than those on the level.

51376°—23—2

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