1. Feeling the Heat – Managing
Risks from Heat Stress at Work
Mike Slater (President Elect)

11. Human beings create heat

12. 100 Watts
200 Watts
800 Watts

13. 100 Watts
200 Watts
800 Watts
The more physically demanding our
activity, the more heat we’re producing

15. We have to lose heat to the environment
– but not too much

17. But we can gain heat from
to the environment too

18. Radiation
Convection

19. Evaporation
Radiation
Convection

20. Heat stroke
Heat exhaustion
Heat syncope
Heat cramps
Prickly heat

21. Heat stroke
Heat exhaustion
Heat syncope
Heat cramps
Prickly heat

22. Source: WHO

23. Heat stroke
Heat exhaustion
Heat syncope
Heat cramps
Prickly heat

24. Evaporation
Radiation
Convection

25. Air
temperature
Humidity
Mean radiant
temperature
Air velocity
These are the environmentl factors we have to
consider when assessing the risk of heat stress

26. Air
temperature
Humidity
Clothing
Mean radiant
temperature
Metabolic
rate
Air velocity

27. Air
temperature
Clothing
Mean radiant
temperature
Acclimatisation
Humidity
Metabolic
rate
Air velocity
And there are other factors we need to consider

28. Air Temperature
Standard thermometer

29. Humidity

31. Radiant heat
Globe thermometer

32. Air Velocity

33. Metabolic rate
1 Met = 58 Wm-2

34. Clothing
1 Clo = Insulation value of 0,155 m2 oC/W

35. Acclimatisation
YES ?
OR
NO?

36. Air
movement
Humidity
Work rate
Mean
radiant
temp.
Air temp.
Clothing
Heat
stress
index
Acclimn

37. A Structured Approach to Heat Stress Risk Assessment
Identify Hazards
Assess Risk
using screening methods
WBGT Index
Identify Controls
Expert analysis
PHS Index
Expert analysis
Physiological measures

38. A Structured Approach to Heat Stress Risk Assessment
Identify Hazards
Assess Risk
using screening methods
WBGT Index
Identify Controls
Expert analysis
PHS Index
Expert analysis
Physiological measures

39. A Structured Approach to Heat Stress Risk Assessment
Identify Hazards
Assess Risk
using screening methods
WBGT Index
Identify Controls
Expert analysis
PHS Index
Expert analysis
Physiological measures

40. Screening methods
Talking to people
Observations
Checklists

42. This looks complicated, but we can probably
identify the risk factors fairly easily

43. A Structured Approach to Heat Stress Risk Assessment
Identify Hazards
Assess Risk
using screening methods
WBGT Index
Identify Controls
Expert analysis
PHS Index
Expert analysis
Physiological measures

44. WBGT Index
Indoors
WBGT = 0.7 tnwb + 0.3 tg
Outdoors
WBGT = 0.7 tnwb + 0.2 tg + 0.1 ta

47. ACGIH TLVs for Heat Stress
Allocation of
work in work Light
cycle
Moderate
Heavy
75% to 100% 31.0
28.0
-
50% to 75%
25% to 50%
0 to 25%
29.0
30.0
31.5
27.5
29.0
30.5
31.0
32.0
32.5
Workload
V ery
heavy
28.0
30.0

50. A Structured Approach to Heat Stress Risk Assessment
Identify Hazards
Assess Risk
using screening methods
WBGT Index
Identify Controls
Expert analysis
PHS Index
Expert analysis
Physiological measures

51. A Structured Approach to Heat Stress Risk Assessment
Identify Hazards
Assess Risk
using screening methods
WBGT Index
Identify Controls
Expert analysis
PHS Index
Expert analysis
Physiological measures

52. Physiological assessment
Temperature
Heart rate

53. Miner’s Core Temperature & Heart Rate
Source: OHTA.

54. The risks here are more complex – an expert
evaluation is likely to be needed

55. A Structured Approach to Heat Stress Risk Assessment
Identify Hazards
Assess Risk
using screening methods
WBGT Index
Identify Controls
Expert analysis
PHS Index
Expert analysis
Physiological measures

56. Hierarchy of Control
Prevention
Engineering
Working Practices
Personal Protection

57. Hierarchy of Control
Prevention
Engineering
Working Practices
Personal Protection
Let’s look at some
examples of typical
controls

58. Insulation of hot surfaces to reduce
radiant and convective heat
www.lubisol.com

59. Extracting hot air

60. Blowing in cool air
http://mikegigi.com

61. Providing protective clothing

62. Regular drinks of water

63. Management Measures
Screening & health surveillance
Information, instruction, training
Supervision
Self regulation
Provide water

64. Hierarchy of Control
Supervision
Prevention
Maintenance
Auditing
Engineering
Working Practices
Personal Protection
Water
Health surveillance
Monitoring
Information
Training

65. Further Information

66. http://www.hse.gov.uk/temperature/thermal/index.htm

67. http://www.bohs.org/resources/res.aspx/Resource/filename/840/TG12.pdf
http://www.bohs.org/resources/res.aspx/Resource/filename/1473/04_TG12_Addendum_to_2nd_Edition.pdf

68. President-elect@bohs.org
www.bohs.org
Twitter: @bohsworld
www.slideshare.net/mikeslater