Monitor Thermal Stress EO 007.02. References Travellers Health, 4 th Edition CF General Safety...

Monitor Thermal Stress

EO 007.02

References

• Traveller’s Health, 4th Edition• CF General Safety Manual, Volume 2, Ch 39• CCOHS - Working in Hot Environments, 2nd

Edition• DAOD 5021-2 Heat Stress (CFAO 34-47) • CF H Svcs Gp PG 4440-10 Heat Stress • CF Heat Stress Pamphlet

Effects of Climatic Extremes

Humans are very adaptable provided they are properly prepared:

-equipment

-acclimatized

-proper, effective PPE and clothing

Environmental Conditions

• Temperature

• Wind Speed

• Moisture

• Radiation


• Temperature: The termoneutral zone for an adult, that is the temperature at which an adult at rest lying on a hammock in the shade wearing scanty clothing, neither gains nor loses heat, is 28°C.

• Temperature above 28°C, or any form of exertion at a temperature near to this value, mean that the body must actively lose heat to maintain a normal core temperature.



• Wind speed in the heat is acceptable as it evaporates sweat and keeps a person cooler. Wind chill in the cold is the opposite and cools too fast.


• Moisture: Water has appro 30 times the thermal conductivity of air and moist air conducts heat much more rapidly than dry air. Humid environments are less comfortable than dry conditions.


• Radiation: Obvious difference in temp from direct sunlight and shaded temp. Less obvious in high altitude where the atmosphere has less chance to attenuate the sunlight.

• These are all factors in the WBGT heat index used to determine work rest cycles.

Climatic Types

Four Main Types:

• Hot and Dry

• Hot and Wet

• Cold and Dry

• Cold and Wet

Climatic Types

• Hot and Dry

• Deserts have low humidity, little rain, scanty vegetation, cloudless skies intense sunshine, and winds that vary from light breezes to violent storms.

Hot and Dry

• At night, clear skies allow rapid heat loss to space by radiation and convection, so there can be heavy dews and occasional frost.

Climatic Types

• Hot and Wet

• Abundant moisture, frequent cloud cover, and shade from tree canopy combine to maintain the temperature at a fairly constant level throughout the year with little variation between day and night.

Climatic Types

• Cold and Dry

• In polar areas shade temperature rarely, if ever, rises above freezing. Much of the land is covered with snow and ice. If the skies are clear there will be brilliant summer sunshine and a lot of radiant heat.

Climatic Types

• Cold and Wet

• Temperate Climates – North America, Western Europe etc. Air Temps between 15 °C and -2 °C are comfortable when dry, but can be hazardous when combined with wind. (Winnipeg for example.)

Body Temp and Control

Homeostasis:

• Maintain a body’s core temp at 37°C (+/ -) 0.5°C

• Core temp can fall when heat loss is greater than heat generation

• Controlled by heat production and heat transfer methods


Heat Production generated through metabolismExamples of heat production - exercise,

involuntary shivering


Heat Transfer from hot to cool body to environment and vice versa 4 main methods

radiation, conduction,convection and evaporation


Radiation all objects radiate heat in the form of

electromagnetic waves. Can be seen with infrared cameras. In the outside environment (cold) we will radiate heat and cool down.


Conduction transfer of heat by direct contact ie

touching metal objects in the winter. Metals and water conduct heat away rapidly.


Convection transport of heat by motion of warmed

gases and liquids. Clothing will help reduce the effects of convection on the body.


Evaporation if the skin surface is wet, the evaporation

of water will cool the skin (sweating). If body temp high, sweat good. If cold, this is bad and it may cool down too rapidly.

modified by: activity, shelter, clothing and technological aids

Occupational Exposure to Cold

• Single most important aspect of life-threatening hypothermia is the fall in the deep core temperature of the body

• Deep core temperature should not fall below 36oC

• Pain in the extremities may be the first early warning of danger to cold stress


Evaluation and Control

• Includes protection/prevention against exposed skin and total body cooling for dry and wet conditions

• Regulations and recommendations are based on outdoor environmental factors ( ie temperatures and wind chill)

Occupational Exposure o Cold

Work-Warming Regimen Below 7oC shelters should be available

and encouraged to use frequently especially with signs of frostbite/frostnip

Warm, sweet drinks to help prevent dehydration and cooling

Buddy system, periodic breaks and warming, clothing, and observation


Workplace Recommendations• Special caution required when dealing

with the cold and:-vibration

-toxic substances ☠-snow and ice (eyes)-predisposed personnel-wind chill


• Progressive clinical presentation of hypothermia:

• General Safety Program Chapter 39 page 39C-7 Appendix A Table 1


• Cooling power of wind on exposed flesh expressed as equivalent temperature:

• General Safety Program Chapter 39 page 39C-8 Appendix B Table 2


• TLV’s work / warm-up schedule for four hour work shift

• General Safety Program Chapter 39 page 39C-9 Appendix C Table 3

Effects of Extreme Cold

• operational needs require some employees to work outdoors in conditions of extreme cold.

• it is important to know how to prevent these effects from occurring, and how to deal with the effects before medical help can be reached.


• Frostbite:– Destruction of body tissues, usually in the

face, hands or feet, by freezing– Circulation of blood in the tissue is

slowed, then stopped– The skin appears a waxy white and

becomes numb– Can lead to destruction of tissue and loss

of fingers or toes


• Hypothermia:– Lowering of body temperature due to the

prolonged exposure to cold– Heat is lost from the body faster than it

can be generated by metabolic activity– Gradual deterioration of body function

leading eventually to loss of consciousness and death


• Trench foot:– Local cooling of the feet– Usually in cold, damp or even wet

conditions, and can occur under conditions less cold than those producing frostbite


Clothing – most important factor is LAYERS!!– maintain layers of warm air around the

body– be worn in a number of layers, so that one

or more items of clothing can be discarded when doing heavy work

– outer layer should be wind-proof


• Clothing —gloves should also be in layers, again with a wind-proof outer layer. Mitts are warmest, but a pair of gloves should be carried for more exacting work– "Mukluk" type footwear is best for the feet,

provided that they will not get wet– protection of the head is essential as this is

where most heat loss occurs. Face masks may also be needed.


• Keeping dry – wet clothing will conduct heat away from

the body – sweating should be avoided by wearing

only enough layers of clothing when working hard, and by opening clothing at the neck

– dry socks should be put on each morning– snow must be brushed off all clothing

before it is put on


Avoid the wind- Build windbreaks or arrange to work on

the lee side of buildings or trees


• Frostbite prevention:– Use buddy system, check each other– Hold his/her bare hand over the affected

area to warm it up– Fingers can be warmed by placing the

hands close to the body, preferably under the armpits

– If feet are frozen, the person should not walk, take the person to warm place, see a doctor


• Hypothermia treatment:– Slow re-warming– Person should be protected from further

heat loss by wrapping in blankets and moving to a medical treatment centre

– Unconscious patients to be handled very gently

– Hot water bottles or other warming devices, should not be more than comfortably warm and not be applied directly to skin

Occupational Exposure to Heat

Introduction

-Based on TLV’s where workers can be exposed without adverse effects

-Acclimatized, fully clothed, and with proper water and salt intake

-WBGT used to monitor

Occupational Exposure to Heat

Adverse Health EffectsHeat related illnesses such as heat

cramps, heat exhaustion and heat stroke

HEAT STROKE most seriousPregnant workers more at risk

Work-Rest Cycle

• also known as workload measurements

• based on heat from the body combined with environmental heat

• TLV’s assume the workplace temperature is similar to the rest place

• based on an 8hr/day, 5 day/workweek

• light, medium and heavy loads

Work-Rest Cycle

• General Safety Program Chapter 39 page 39B-2 Table 1

Metabolic Rates

• General Safety Program Chapter 39 page 39B-11 Table 8

Acclimatization

• Clothing: – light summer clothing as customarily worn

by workers when working under hot environmental conditions.

– if special clothing is required for performing a particular job and this clothing is heavier or it impedes sweat evaporation or has higher insulation value, the worker’s heat tolerance is reduced

Acclimatization

• Acclimatization and Fitness:– TLVs are valid for acclimated workers who

are physically fit – extra caution must be employed when

unacclimatized or physically unfit workers must be exposed to heat stress conditions.

Acclimatization

• Heat Acclimatization – heat acclimatization is acquired only

gradually, being fully achieved over up to three weeks of continued physical activity under heat stress conditions similar to those anticipated for future work

Water/Salt Supplementation

• Drinking water should be available and close enough to the work area

• 150 ml every 15-20 mins and cool 10-15oC

• Advised to use extra salt in food or water

• “sport drinks” not actually mentioned

Prevention

• Profuse and prolonged sweating should be eliminated for long-term routine tasks

• Can produce dehydration and loss of body electrolytes

• May lead to heat exhaustion or muscle cramps

• Can also disturb normal cardiovascular functions

Prevention

• Heat stress management must always be the prevention of heat stroke, which is life-threatening and the most serious of the heat-induced disabilities

• Victim’s skin is hot and dry, sweating has ceased, and the body temperature may be 40 deg C or higher

• Immediate emergency care is needed

Heat Stress Policy

• DAOD 5021-2 Heat Stress Policy

• The WBGT Index has been selected by the CF Advisory Group as the one instrument to be used in describing physiological environments for the CF, and it shall be employed to express environmental heat stress.

Responsibility Table

• Responsibilities (Where heat stress is suspected)• a. D Med Svcs will develop documentation

and training pertaining to the recognition, prevention and treatment of heat stress.

• b. Any member/supervisory staff will adopt preventive measures to minimize the risk of heat stress when conducting physical activities in a hot environment.


Every CF or DND employee will take the following action when heat stress is suspected:

• remove the victim from activity, • administer F/A, • asses the condition or have it assessed by

competent personnel, and• take action to avoid further complication.


• The Unit PMed Tech will be responsible for measuring the WBGT Index and reporting the results to the Base Surgeon when reading levels exceed a value of 27°C.

• The Base/Wing/Fleet Surgeon shall report the results to the CO of the Unit and advise him of its effect on personnel, so that preventive measures may be implemented

WBGT Use

• Heat Stress Guidelines:

• Recognition and Prevention pamphlet

Control Measures

Engineering Controls

-most effective Administrative Controls Personal Protection

Control Measures

• Engineering controls include:– Reducing Metabolic Heat Production

(heat produced by the body): minimize the need for heavy physical work and the resulting build up of body heat.

– Reducing the Radiant Heat Emission from Hot Surfaces: Covering hot surfaces with sheets of low emissivity material such as aluminum or paint that reduces the amount of heat radiated from this hot surface into the workplace.

Control Measures

• Insulating Hot Surfaces: Insulation reduces the heat exchange between the source of heat and the work environment.

• Shielding: Shields stop radiated heat from reaching work stations.

Control Measures

• Ventilation and Air Conditioning: Ventilation, localized air conditioning, and cooled observation booths are commonly used to provide cool work stations. Cooled observation booths allow workers to cool down after brief periods of intense heat exposure while still allowing them to monitor equipment.

• Reducing the Humidity: Air conditioning, dehumidification, and elimination of open hot water baths, drains, and leaky steam valves help reduce humidity.

Control Measures

• Admin Controls include:

• Acclimatization,

• work-rest cycles,

• water/salt,

• education,

• and first aid

Control Measures

• Personal Protection Ordinary clothing provides some protection from heat radiated by surrounding hot surfaces. Specially designed heat-protective clothing is available for working in extremely hot conditions. In hot and humid workplaces, light clothing allows maximum skin exposure and efficient body cooling by sweat evaporation.

Control Measures

• Workers who move back and forth between very hot, dry indoor environments and cold winter outdoor environments find that long underwear moderates the extremes in temperatures.

• Eye protection which absorbs radiation is needed when the work involves very hot objects, such as molten metals and hot ovens.

Control Measures

• Work that requires the wearing of impermeable clothing presents an added heat burden as the clothing reduces the body's ability to dissipate heat. Under such circumstances, it is often necessary to reduce the exposure limit values of WBGT to levels below those appropriate for workers wearing light clothing.

WBGT Standards

General Guidelines:

A WBGT Index reading of 27°C has been designated as the maximum figure for a normal working and living environment to which personnel should be exposed

WBGT Standards

Readings above 27C

The higher the temperature, the higher the humidity, the greater the physical activity and/or the more critical the task then the shorter the safe exposure time.

WBGT Standards

• WBGT Index reading 27°C - 29.5°C

• These are marginal conditions for conducting moderate to severe physical activities or critical tasks. There must be alertness in non-acclimatized personnel.

WBGT Standards

• WBGT Index reading 29.5°C - 31°C

• Heat stress can be expected in personnel conducting moderate to severe physical activities or critical tasks. These activities should be curtailed as required; particularly for non-acclimatized personnel

WBGT Standards

• WBGT Index reading over 31°C

• Moderate to severe physical activities or critical tasks should be suspended. Other

activities should be curtailed as required.

WBGT Standards

• when the WBGT Index reading is above 29.5C, every effort should be made to reduce the adverse effects of excessive heat on personnel engaged in moderate to severe physical work or critical tasks (by reducing the time on duty, increasing rest periods, etc.).

• In addition, medical advice should be requested when potential heat stress situation exists in any operational activity.

Conclusion

• Thermal stress is a common problem, as the extremes of both hot and cold can be dangerous

• Keep in mind that a change in the body’s core temperature will impair performance greatly

Questions?

Monitor Thermal Stress EO 007.02. References Travellers Health, 4 th Edition CF General Safety...

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