Heat Control in the Workplace

Transcription

1 Heat Control in the place Effective Date: November 2003 Revised: 0

2 HEAT CONTROL IN THE WORKPLACE Wilfrid Laurier University 1.0 Purpose of the Heat Control Program The intention of this program is to provide a basic understanding of the effects of heat on the body, the monitor of heat exposure and methods of preventing heat-related illness from occurring. 2.0 What is Heat Stress? Normal body temperature is 37 Celsius (98.6 Fahrenheit). For the body to work well this temperature must remain constant. The body removes heat through the skin when heat increases. Blood vessels near the skin open up to bring more warm blood to the surface. Heat then escapes and the body cools. The main source of cooling, when the temperature is high, is the evaporation of sweat. However, when the humidity is high, sweat does not evaporate as quickly and has little or no cooling effect. Heat stress is the overloading of the body s cooling system. When heat is combined with other stresses such as hard physical work, loss of fluids, fatigue or some medical conditions, it may lead to heatrelated illness, disability and even death. The signs and symptoms of heat stress are: feeling faint, dizziness, light to mild headache, cramps or a rash. 3.0 Legal Requirements on Thermal Comfort The Ontario Ministry of Labour states that under section 25(2)(h) of the Occupational Health and Safety Act, employers have a duty to take every precaution reasonable in the circumstance for the protection of a worker. It is recommended, for compliance purposes, that the Threshold Limit Values (TLVs) for Heat Stress and Heat Strain published by the American Conference of Governmental Industrial Hygienists (ACGIH) be followed. These values are based on preventing unacclimatized workers core temperatures from rising above 38 C.

3 ACGIH HEAT STRESS GUIDELINE Screening Criteria for Heat Stress Exposure (WBGT values in C) Acclimatized Unacclimatized Demands Light Moderate Heavy Very Heavy Light Moderate Heavy Very Heavy 100% % % Rest 50% % Rest 25% 75% Rest CSA Standard Z Sect Relevant Parameters for Thermal Comfort Individual differences make it difficult to provide a thermal environment that will satisfy everyone, even if all persons wear the same clothing and perform the same activity. Acceptable working temperatures depend mainly on activity level and clothing. ers my feel lethargic, or tire quickly, in an office that is too warm. While in an office that is too cold, workers may feel restless and easily distracted. 5.0 ASHRAE Standard Thermal Environmental Conditions for Human Occupancy Optimum temperature ranges are suggested in ASHRAE Standard 55, based on accommodating 80% of individuals. The following table shows recommended acceptable temperature ranges at relative humidity (RH) of 50% and air speed of less than 0.15 m/sec.

4 ACCEPTABLE TEMPERATURES Season Clothing Temperature Winter Heavy pants, long C sleeved shirt and/or sweater Summer Light pants, short sleeved shirt C NOTE: ISO has a slightly broader range: winter C and summer C. An increased humidity can give the perception of a higher temperature. However, for sedentary work in moderate temperatures (20-26 C), the influence of humidity is quite modest. Too low of humidity (less than 20%) brings the risk of dryness. If the humidity is too high (greater than 70%), there is a risk of condensation. It also makes the office feel stuffy. Humidex is used by the weather forecast service of Environment Canada to inform the public about how hot it is outdoors. Occasionally it is used to warn indoor employees in non-air conditioned workplaces. HUMIDEX AND THERMAL COMFORT Humidex Range ( C) Degree of Comfort Comfortable Varying degrees of discomfort Uncomfortable 46 and Over Many types of labour must be restricted ONTARIO HEALTH AND SAFETY REGULATIONS WITH RESPECT TO THERMAL CONDITIONS IN THE WORKPLACE Construction projects: Change room for underground workers chamber Medical locks Industrial Establishment Regulations: Enclosed workplace 27 C min. 38 C max 18 C min./27 C max. 18 C min.

5 6.0 Responsibilities under the Heat Control Program Supervisors Supervisors must be familiar with the hazards and standard approaches to work related with the specific hot environments under his/her authority, the education and training requirements for safety while working in these environments, and the suitable standard operating procedures for all such location under his/her authority. He/She has the following responsibilities: To identify all hot work environments under his/her authority To ensure that the hazards, symptoms of heat-induced disorders, and standard operating procedures for working in hot environments are made known to employees To ensure that all employees perform in accordance with the standard operating procedures for hot work environments To ensure that all employees use the appropriate equipment and materials for working in hot environments To promptly report known or suspected heat related incidents to the Environmental/Occupational Health and Safety Office. Employees Employees have the following responsibilities: To be familiar with the hazards associated with working in hot environments, the symptoms of heat related disorders and the pertinent standard operating procedures for the environment To work according to the standard operating procedures for working in hot environments To use the appropriate equipment and materials provided for working in hot environments To promptly report any known or alleged accidents, unsafe conditions or unsafe procedures to his/her supervisor

6 7.0 Heat-Induced Disorders Too much heat in a very hot work environment can cause a variety of acute health effect. They include the following: Heat Rashes Heat rashes are caused by hot humid environments and/or plugged sweat glands. Heat rashes are characterized by tiny, blister-like red vesicles on the skin accompanied by prickling sensations during heat exposure. Sunburn Sunburns are caused by too much exposure to the sun. Sunburns are characterized by red, painful, or blistering and peeling skin. Heat Cramps Heat cramps are painful, involuntary muscle spasms that usually occur during heavy exercise in hot environments. In adequate fluid intake often contributes to this problem. The spasms may be more intense and more prolonged than typical nocturnal leg cramps. Heat Syncope Heat syncope is heat-induced dizziness and fainting that occurs while a person is immobile and standing upright. It results from pooling of blood in the legs and occurs mostly among unacclimatized people. Heat Exhaustion Heat exhaustion is when inadequate salt and water intake causes a person s body s cooling system to start to break down. Heat exhaustion is characterized by heavy profuse sweating, cold moist (clammy) skin, weak pulse, nausea, dizziness, weakness, headache, blurred vision, clumsy, upset or confusion, is very thirsty, or is panting and breathing rapidly may lead to unconsciousness, coma and death. Heat Stroke Heat stroke is the most serious heat stress disorder. It results from sustained exertion in hot environments by unacclimatized workers. Its cause is partial or complete failure of perspiration following sweat gland fatigue, which leads to a loss of evaporative cooling and a rapid rise in core body temperature. Heat stroke is characterized by elevated

7 temperature generally greater than 40 C with hot, dry skin and changes in mental status ranging from personality changes to confusion and coma. Other signs may include: rapid heartbeat, rapid and shallow breathing, elevated or lowered blood pressure, cessation of sweating, irritability, confusion or unconsciousness. Heat stress can also have long-term chronic effects ers who have suffered heat stroke or exhaustion are often less able to tolerate heat, sometimes for the rest of their lives After labouring for long periods in a hot environment, some workers will experience chronic heat exhaustion, while others may suffer from hypertension (high blood pressure), heart muscle damage, reduced libido, or sexual impotence. 8.0 Control Measures In order to minimize and moderate heat related disorders and safety issues, The Ministry of Labour (MOL) Guidelines for heat Stress are to be followed. The MOL guidelines outline preventative measures for various heat related disorders, as well as engineering and administrative controls for working in hot environments. The preventative measures and controls implemented will be based on the specific environment and tasks associated with each individual department. Engineering Controls Reduce physical demands of work task through mechanical assistance (hoists, lifting tables, etc.) Increase air movement if temperature is less than 35 C (fans) Provide cool work areas Provide air-conditioned rest areas Reduce the temperature and humidity through air cooling Exhaust hot air and steam produced by operations Control the heat at its source through the use of insulating reflective barriers (e.g. insulate furnace walls) Administrative Controls The employer should assess the demands of all jobs and have monitoring and control strategies in place for hot days and hot workplaces Increase the frequency and length of rest breaks Schedule strenuous jobs to cooler times of the day

8 Provide cool drinking water near workers and remind them to drink a cup every 20 minutes or so Caution workers to avoid direct sunlight Assign additional workers or slow down the pace of work Make sure everyone is properly acclimatized Train workers to recognize the signs and symptoms of heat stress and start a buddy system since people are not likely to notice their own symptoms. Pregnant workers and workers with a medical condition should discuss working in the heat with their doctor. First Aid responders and an emergency response plan should be in place in the event o f a heat-related illness. Investigate any heat-related incidents Personal Protective Equipment Light summer clothing should be worn to allow free air movement and sweat evaporation Outside, wear light-coloured clothing In a high radiant heat situation, reflective clothing may help For very hot environments, air, water or ice-cooled insulated clothing should be considered. Vapour barrier clothing, such as chemical protective clothing, greatly increases the amount of heat stress on the body, and extra caution is necessary. Additional Recommendations ers should salt their food well, particularly while they are acclimatizing to a hot job Avoid beverages containing caffeine like cola, tea and coffee as these cause dehydration Close window coverings where available