12.2.2.1-1 Engineering Controls

Engineering controls should be applied where heat and humidity may impair the effectiveness or threaten the wellbeing of workers.

Additional Information: Examples of engineering controls include: shielding or insulating sources of radiant heat, eliminating steam leaks, increasing ventilation, and providing assists to reduce the strenuousness of the task. Table 12.6 gives temperature ranges intended to minimize performance decrements and potential harm to workers because of excessive heat. The temperature ranges in the table are ceiling values (i.e., they assume that protective practices (such as acclimatization, training, and a cool place to rest) are in place). In general, for areas requiring frequent operational or maintenance activities, air conditioning should be provided, when feasible, if temperatures exceed 29.5 degrees C

(85.1 degrees F). In addition, adequate ventilation should be provided in equipment trailers or other locations where personnel are performing monitoring, servicing, or other maintenance tasks. Work practices also should be adopted to minimize risk caused by heat exposure that cannot be eliminated by engineering controls. Recommended work practices include training in the recognition and treatment of heat illnesses, water and salt replacement, acclimation, and work/rest cycles (stay times). Table 12.7 contains illustrations of how temperature (wet-bulb globe temperature (WBGT)), metabolism, and clothing relate to stay times. The times in the table are ceiling values (i.e., they assume that protective practices (such as acclimatization, training, and a cool place to rest) are in place.0700, 6146, 1472G

 

 

 

Table 12.6 Ranges of WBGT In Oc (Of) For Different Ranges Of Stay Times

 

Stay Time

Work Clothes

Cotton Coveralls

Double Cottons

Cottons plus Plastics

Metabolism

Metabolism

Metabolism

Metabolism

Low

Mod

High

Low

Mod

High

Low

Mod

High

Low

Mod

High

0-15

50-52

42-50

38-42

48-50

41-49

37-41

46-48

38-46

34-38

44-46

36-44

32-36

 

(122-

(108-

(100-

(118-

(106-

(99-

(115-

(100-

(93-

(111-

(97-111)

(90-97)

 

126)

122)

108)

122)

120)

106)

118)

115)

100)

115)

 

 

15-30

44-50

36-42

32-38

42-48

35-41

31-37

40-46

32-38

28-34

38-44

30-36

26-32

 

(111-

(97-108)

(90-100)

(108-

(95-106)

(89-99)

(104-

(90-100)

(82-93)

(100-

(86-97)

(79-90)

 

122)

 

 

118)

 

 

115)

 

 

111)

 

 

20-45

42-48

34-38

31-34

40-46

33-37

30-33

38-44

30-34

27-30

36-42

28-32

25-28

 

(108-

(93-100)

(89-93)

(104-

(91-99)

(86-91)

(100-

(86-93)

(81-86)

(97-108)

(82-90)

(77-82)

 

118)

 

 

115)

 

 

111)

 

 

 

 

 

30-60

40-44

33-36

30-32

38-42

32-35

29-31

36-40

29-32

26-28

34-38

27-30

24-26

 

(104-

(91-97)

(86-90)

(100-

(90-95)

(84-89)

(97-104)

(84-90)

(79-82)

(93-100)

(81-86)

(75-79)

 

111)

 

 

108)

 

 

 

 

 

 

 

 

45-90

38-42

32-34

29-31

36-40

31-33

28-30

34-38

28-30

25-27

32-36

26-28

23-25

 

(100-

(90-93)

(84-89)

(97-104)

(89-91)

(82-86)

(93-100)

(82-86)

(77-81)

(90-97)

(79-82)

(73-77)

 

108)

 

 

 

 

 

 

 

 

 

 

 

60-

36-40

30-33

28-30

34-38

29-32

27-29

32-36

26-29

24-26

30-34

24-27

22-24

120

(97-104)

(86-91)

(82-86)

(93-100)

(84-90)

(81-84)

(90-97)

(79-84)

(75-79)

(86-93)

(75-81)

(72-75)

90-3h

34-38

29-32

27-31

32-36

28-31

26-30

30--34

25-28

23-27

28-32

23-26

21-25

 

(93-100)

(84-90)

(81-89)

(90-97)

(82-89)

(79-86)

(86-93)

(77-82)

(73-81)

(82-90)

(73-79)

(70-77)

2h-4h

32-36

28-30

26-28

30-34

27-29

25-27

28-32

24-26

22-24

26-30

22-24

20-22

 

(90-97)

(82-86)

(79-82)

(86-93)

(81-84)

(77-81)

(82-90)

(75-79)

(72-75)

(79-86)

(72-75)

(68-72)

 

 

 

 

Table 12.7 Stay Times In Minutes (Or Hours “H”) For Different Wbgts

 

Wet-Bulb Globe Temp

Work Clothes

Cotton Coveralls

Double Cottons

Cottons Plus Plastics

Metabolism

Metabolism

Metabolism

Metabolism

C

F

Low

Mod

High

Low

Mod

High

Low

Mod

High

Low

Mod

High

50

122

15-30

0-10

 

5-15

0-5

 

5-15

 

 

 

 

 

48

118

20-45

5-15

 

15-30

5-10

 

10-20

 

 

5-15

 

 

46

115

20-45

5-20

 

20-45

5-15

 

15-30

0-10

 

15-20

 

 

44

111

30-60

10-25

 

20-45

5-20

 

20-45

5-15

 

15-30

0-10

 

42

108

45-90

15-30

5-10

30-60

10-25

 

20-45

5-20

 

20-45

5-15

 

40

104

60-90

15-45

10-20

45-90

15-40

5-10

30-60

10-25

 

20-45

5-20

 

38

100

90-120

20-45

15-30

60-90

15-45

10-25

45-90

15-30

5-10

30-60

10-25

 

36

97

2h-4h

30-60

15-40

90-120

25-45

15-30

60-90

15-45

10-20

45-90

15-30

5-10

34

93

3h-8h

45-90

20-45

2h-4h

30-60

15-45

90-120

20-45

15-30

60-90

15-45

10-20

32

90

>8h

90-120

30-60

3h-8h

60-100

25-50

2h-4h

30-60

15-40

90-120

20-45

15-30

30

86

>8h

2h-4h

60-120

>8h

1h-2h

30-90

3h-8h

45-90

20-45

2h-4h

30-60

15-40

28

82

>8h

>8h

2h-4h

>8h

1h-4h

lh-3h

>8h

90-120

30-60

3h-8h

45-90

20-45

26

79

>8h

>8h

4h-8h

>8h

>8h

3h-8h

>8h

2h-4h

60-120

>8h

90-120

30-60

24

75

>8h

>8h

>8h

>8h

>8h

>8h

>8h

>8h

2h-4h

>8h

2h-4h

60-120

22

72

>8h

>8h

>8h

>8h

>8h

>8h

>8h

>8h

4h-8h

>8h

>8h

2h-4h

20

68

>8h

>8h

>8h

>8h

>8h

>8h

>8h

>8h

>8h

>8h

>8h

4h-8h

<20

<68

>8h

>8h

>8h

>8h

>8h

>8h

>8h

>8h

>8h

>8h

>8h

>8h