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
Environmental Conditions • 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.
Environmental Conditions • 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.
Environmental Conditions • 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.
Environmental Conditions • 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.
Environmental 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
Body Temp and Control Heat Production • generated through metabolism • Examples of heat production - exercise, involuntary shivering
Body Temp and Control Heat Transfer • from hot to cool • body to environment and vice versa • 4 main methods • radiation, • conduction, • convection and evaporation
Body Temp and Control • 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.
Body Temp and Control • Conduction • transfer of heat by direct contact ie touching metal objects in the winter. Metals and water conduct heat away rapidly.
Body Temp and Control • Convection • transport of heat by motion of warmed gases and liquids. Clothing will help reduce the effects of convection on the body.
Body Temp and Control • 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
Occupational Exposure to Cold 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
Occupational Exposure to Cold Workplace Recommendations • Special caution required when dealing with the cold and: -vibration -toxic substances ☠ -snow and ice (eyes) -predisposed personnel -wind chill
Occupational Exposure to Cold • Progressive clinical presentation of hypothermia: • General Safety Program Chapter 39 page 39C-7 Appendix A Table 1
Occupational Exposure to Cold • Cooling power of wind on exposed flesh expressed as equivalent temperature: • General Safety Program Chapter 39 page 39C-8 Appendix B Table 2
Occupational Exposure to Cold • 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.
Effects of Extreme Cold • 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
Effects of Extreme Cold • 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
Effects of Extreme Cold • 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
Effects of Extreme Cold • 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
Effects of Extreme Cold • 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.
Effects of Extreme Cold • 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
Effects of Extreme Cold • Avoid the wind- • Build windbreaks or arrange to work on the lee side of buildings or trees
Effects of Extreme Cold • 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
Effects of Extreme Cold • 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 Effects • Heat related illnesses such as heat cramps, heat exhaustion and heat stroke • HEAT STROKE most serious • Pregnant 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