Heat Stress UW-EC Facilities Planning & Management By: Chou Lor
Heat Stress • Training Objectives: • Background Factors • Heat Stress Hazards • Heat Stress Control Measures • Prevention of Heat Stress
Heat Stress • What is Heat Stress? • The combination of environmental and physical work factors that constitute the total heat load imposed on your body’s cooling system.
Heat Stress • Body’s Cooling System • Blood is pumped close to skin for cooling reducing blood going to the brain and rest of your body. • As temperatures rise, surface blood vessels get bigger and pulse rate goes up. • As temperatures rise your body gains heat instead of losing it.
Heat Stress • Body’s Cooling System Cont. • Most people lose about a quart of sweat/hr in extreme heat. • This adds a strain to your circulatory system which now has to lower the amount of blood in your body.
Heat Stress Mechanisms for heat loss/transfer Evaporation Radiant Heat Convection Conduction
Heat Stress • Background – Heat Exchange • Mechanisms for heat loss/transfer • Evaporation • The body transfers water vapor to the skin through pores and sweat glands
Heat Stress • Background – Heat Exchange Cont. • Mechanisms for heat loss/transfer • Conduction • The direct transfer of heat from skin to the surrounding air as the ambient temp rises • Convection • Air blowing over the skin e.g. use fan • Radiation • The transfer of heat to or from surrounding objects that are not in direct contact with the body
Most Severe 5. Heat Stroke 5 4 3 2 1 4. Heat Exhaustion 3. Heat Cramps 2. Heat Fatigue 1. Heat Rash Least Severe Heat Stress • Types of Heat Stress:
Heat Stress • Heat Stress Hazards Cont. • Heat Rash • Cause • Hot humid environment • Skin is constantly wet from sweat • Sweat gland ducts become plugged • Signs & Symptoms • Painful or itchy skin • Blister-like rash • Treatment • Keep skin clean and dry • Stay cool with air conditioning • Fans and cool showers • Wear lightweight & loose-fitting clothing • Prevention • Shower after working in hot environment • Keep skin clean and dry
Heat Stress • Heat Stress Hazards Cont. • Heat Fatigue • Cause • Lack of acclimatization • Depletion of water and salt due to sweating • Signs & Symptoms • Discomfort • Feeling of weakness and tiredness • Impaired performance of skilled tasks in heat • Inability to concentrate • Treatment • No treatment necessary unless other signs of heat illness are present • Prevention • Acclimatization of workers for work in the heat
Heat Stress • Heat Stress Hazards • Heat Cramps • Cause • Heavy sweating during hot work, drinking large amount of water without replacing salt loss • Signs & Symptoms • Painful muscle spasms of arms, legs and stomach • Usually occur after heavy sweating and may begin towards the end of the workday • Treatment • Drink water, move to a cool shaded area • Spray the person with water and massage the cramp • Adequate salt intake at meals, try eating more fruits • Prevention • Adequate salt intake with meals, and adequate water intake • Drink fluids regularly
Heat Stress • Heat Stress Hazards Cont. • Heat Exhaustion • Cause • Dehydration causes blood volume to decrease • Inadequate salt and water intake causes a person’s body’s cooling system to break down • Signs & Symptoms • Fatigue, weakness, dizziness, faintness • Nausea, headache, heavy sweating • Low to normal blood pressure • Treatment • Move person to a cool shaded area • Provide cool water to drink • Fan and spray with cool water • Prevention • Acclimatize worker using a work rest • Drink plenty of water
Heat Stress • Heat Stress Hazards Cont. • Heat Stroke • Cause • Partial or complete failure of sweating mechanism • Body cannot get rid of excess heat • Sign & Symptoms • Hot dry skin, elevated body core temperature, confusion, loss of consciousness • Fatal if treatment is delayed • Treatment • Medical emergency • Move the victim to a cool shady area • Remove excess clothing • Spray the person with cool water • Prevention • Monitor workers in sustained work in severe heat • Drink plenty of water • Drink cool fluids that do not contain caffeine
Heat Stress • Heat Stress Control Measures • Engineering Controls • Reduction of Humidity: • Reduce the temperature and humidity through air conditioning • Provide air-conditioned rest areas. • Ventilation and Air Conditioning: • Use of air-circulating fans • Better ventilation, to draw heat and steam away from work areas • Shielding between workers and heat sources
Heat Stress • Heat Stress Control Measures • Administrative Controls • Changing the rate of work • Schedule hot jobs to cooler times of the day. • Increase the frequency and length of rest breaks if possible • Encouraged employees to take a rest break should any sign of heat stress or heat disorder develop. • Allow for slower-paced work during the hottest periods of the day • Limiting duration of exposure time • Rotate work activities
Heat Stress • Heat Stress Control Measures Cont. • Protective Clothing • Light summer clothing should be worn to allow free air movement and sweat evaporation. • Outside, wear light-colored clothing.
Heat Stress • Prevention of Heat Stress • Supervisor • Identify all hot work environments under his/her authority • Ensure that employees have been trained in hot working environments • Train workers to recognize signs & symptoms of heat stress disorders and be prepared to give first aid if necessary. • Avoid placing employees in hot work environments for extended time periods. Realize individual employees vary in their tolerance to heat stress conditions.
Heat Stress • Prevention of Heat Stress • Employees • Learn to recognize the symptoms of heat stress. Change work location, taking adequate rest periods (in shade or cooler environment). • Become familiar with the hazards associated with working in hot environments • Use adequate fans for ventilation and cooling, especially when wearing personal protective equipment (PPE). • Wear light colored, loose (unless working around equipment with moving parts) clothing. • Keep shaded from direct heat where possible (e.g., wear a hat in direct sunlight). • Drink plenty of water. In hot environments the body requires more water than it takes to satisfy thirst.
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