Heat Stress Guideline

Transcription

1 Heat Stress Guideline Introduction: The purpose of this guideline to establish a Heat Stress Response Plan to ensure safe working conditions in extreme heat conditions and reduce the potential risk of heat induced illness during periods of hot and humid weather. Scope: This guideline applies to all Covenant Health employees who may be exposed to heat, in indoor environments, during their work. It also applies to external workers (e.g. student, contractors) who may be contracted to work in hot environments for Covenant Health. What is heat stress? Everyone at some time or another manages heat stress. Managing heat stress is a natural function of the human body. When the body is in a warm, hot environment, the temperature of the body rises. The body must lower this effect through relief of heat; this is done through the evaporation of sweat produced from the body. If the body is unable to cool itself through this method, the body s core temperature increases above 38 C. A rise in the core body temperature can lead to the heat stress disorders. There are several common heat-related disorders. Some are more severe than others. Heat rash occurs when blocked sweat glands become inflamed. This painful rash reduces the body's ability to sweat and to tolerate heat. Heat cramps are painful spasms of the muscles. The muscles used in doing the work are most susceptible. The spasms are caused by the failure of the body to replace its lost body salts and usually occur after heavy sweating Heat exhaustion results when the body loses large amounts of fluid by sweating during work in hot environments. The skin becomes cool and clammy. Symptoms include profuse sweating, weakness, dizziness, nausea, and headaches.

2 Heat faint is heat-induced giddiness and fainting induced by temporarily insufficient flow of blood to the brain while a person is standing. It occurs mostly among unacclimatized people. It is caused by the loss of body fluids through sweating, and by lowered blood pressure due to pooling of blood in the legs. Heat stroke is the most serious condition and requires immediate medical attention. The body temperature becomes very high (even exceeding 41 C).Complete or partial loss of consciousness is possible. Sweating is not a good symptom of heat stress as there are two types of heat stroke -- "classical" where there is little or no sweating (usually occurs in children, persons who are chronically ill, and the elderly), and "exertional" where body temperature rises because of strenuous exercise or work and sweating is usually present. Primary parameters contributing to heat stress Many variables contribute to heat stress. To prevent heat stress, employees must be able to identify all sources of heat and understand how the body removes excess heat. Generally speaking, the following parameters contribute to induced heat stress disorder: High temperature High humidity Work load Clothing effects Physical conditions heat stress While heat stress is commonly associated with warm weather, it can occur any time the temperature is above normal. Some factors involved in causing heat stress are: 2 P a g e

3 Managing Heat Stress in the Workplace Heat stress risk can be removed or reduced from the workplace by following these measures: o Controlling the temperature using engineering solutions, such as process changes, use fans or air conditioning, use physical barriers that reduce exposure to radiant heat. o Providing mechanical aids where possible to reduce the work rate o Regulating the length of exposure to hot environments o Preventing dehydration o Providing personal protective equipment o Acclimatizing employees o Provide training for employees (especially new and young employees), educate them about the risks of heat stress associated with their work, what symptoms to look out for, safe work practices, and emergency procedures o Identify employees who are more susceptible to heat stress because of an illness, condition or medication that may contribute to the early onset of heat stress, eg pregnant women or those with heart conditions. 3 P a g e

4 Acclimatizing Employees The human body will adapt to working in a hot environment if it is given a chance to gradually get used to the new conditions. This process, known as acclimatization, allows the body to modify its own function to better cope with heat stress and to remove excess heat more efficiently. Much of this adjustment to heat, under normal circumstances, usually takes about 5 to 7 days, during which time the body will undergo a series of changes that will make continued exposure to heat more endurable. However, it may take up to several weeks for the body to fully acclimatize. Wet Bulb Globe Temperature (WBGT) WBGT is an index used to quantify the true level of heat stress on an individual from the combined effects of air temperature, humidity, air movement, and radiant heat. The index is the most widely used and accepted index for the assessment of heat stress in work places. Measuring Heat Stress The humidex is a temperature index designed to describe how work environment feels to employees. The index value takes into account the air temperature, combines it with the humidity in the air, and produces a value which is how warm it feels outside. The humidex is used as a measure of perceived heat that a person feels. It does not account for personal factors, acclimatization, or clothing. Environment Canada has published a heat stress reference chart that translates WBGT values from heat stress Threshold Limit Values (TLV) into Humidex units. This can determine readings for indoor areas and process-related heat by taking a measurement of the temperature and relative humidity, and cross referencing it to this chart. The humidex value can be used for measuring heat stress in the work places. Humidex Based Heat Response Plan The Humidex plan is a simplified way of protecting employees from heat stress which is based on the American Conference of Governmental Industrial Hygienists (ACGIH) Heat Stress TLV. Wet Bulb Globe Temperatures were translated into Humidex based on the moderate work load category & assuming workers are unacclimatized (see rationale at the end of the document) 4 P a g e

5 Heat Response Procedures: 1) As a practical applied process, the supervisor must adhere to the following procedure when assigning work, to determine what controls need to be implemented and communicated with employees: o Use a regular thermometer and an accurate humidity meter o Measure the actual air temperature and humidity in the intended work area o Refer to Humidex Chart (see Appendix A) to determine the Humidex level o Classify the work (see Appendix B) o Based on the determined Humidex Level and the work classification, administer controls as outlined in Table 2 (See Appendix C) o o Enter all readings in the Field Temperature and Humidity Measurements form (attached). Upon completion of the work, the supervisor of the work will be responsible for submitting the Form to JWHS committee, for filing for short period of time(if temperature rise above 29 C) Clothing and Personal Protective Equipment: Personal Protective Equipment must be worn as required by the task being performed. If possible, employees should wear light clothing that allows air to move freely and sweat to evaporate. 2) Work in hot environments should not be conducted alone. A buddy system should be used to monitor symptoms of heat related illness and ensure adherence to the program (i.e. taking water breaks) 3) Jobs requiring heavy work should be scheduled at cooler times of the day. 4) In situations such as heat waves (3 or more days of temperature of 32C or more) where the employee will be working continuously in a hot environment, supervisors are responsible for ensuring their employees are acclimatized based on the following criteria: o If the employee is experienced on the job, their time in hot environments must be limited to 50% of the shift on the first day, 60% of the shift on the second day and 80% of the shift on the third day. On the fourth day a full shift can be worked. 5 P a g e

6 o If the employee is not experienced on the job they should spend 20% of their time working in hot conditions on the first day and increase their time by 20% each subsequent day. 5) When applicable, reduction of physical demands of work tasks should be done through mechanical assistance where possible (hoist, carts, etc.). 6) Employees should be provided with water or other fluids and be reminded to drink a cup approximately every 20 minutes. 7) Employees should take more frequent and longer breaks if possible in shaded and cooler areas. 8) Employees with heat stress symptoms will receive first aid care if necessary based on symptoms and severity of their heat stress. 9) Employee reporting procedures: o If employees have any concerns about the hazards of heat stress, they should inform their supervisor o If a situation arises where a warm environment affects a previously existing medical condition (i.e. asthma); employees should consultant with a physician. o If the heat issue remains unresolved, employees should inform their supervisor or consult with Covenant Health OHS Department at Please contact me if you have any questions or concerns regarding this guideline at (780) , or by at Matthew.Godarzi@covenanthealth.ca Matthew Godarzi Safety and Hygiene Consultant OHS, Covenant Health 6 P a g e

7 Appendix A Below, is a table from the Occupational Health and Safety indicating air temperature on the Y-axis and relative humidity on the X-axis. Read the Humidex from the following chart by finding the number where the temperature (ºC) intersects with the relative humidity (%). (For example, an air temperature of 29 C with a relative humidity level of 60% yields a feeling of 37 C) 7 P a g e

8 Appendix B Work Activity Levels Categories and Examples A significant contributor to heat stress is the amount of heat generated by the metabolic activity of the individual, which is why the Heat Stress Guidelines are linked to the activity level or work load: Activity Level or Work Load Rest Light Work Moderate Work Heavy Work Work Activities Sitting quietly or with moderate arm movements (e.g.: reading, working at a computer, attending meeting or lecture, watching training video) Light work such as, sitting or standing to control equipment, performing light hand or arm, work with occasional walking (e.g.: laboratory analyses, giving a lecture, completing an area inspection), driving a car, specimen collection, preparing and escorting patients for transfer, disassembling and repairing of smaller part on work table, pushing and pulling wheelchair without patients, changing bed linens, and gathering medical supplies. Moderate work such as, lifting moderately, walking with moderate pushing or pulling, walking at a moderate pace, rolling patients on stretchers, scrubbing in a standing position, sweeping floors, portering patients on stretchers or wheelchairs, operating a walk-behind lawn mower, or field work requiring the carrying of equipment with use of trolley. Intense work, such as, walking at a fast pace, frequent patient handling, and frequent manual material handling. Very Heavy Work Very intense activity at fast to maximum pace (e.g.: shoveling wet sand, maximum sports exertion such as running a 400 metre race) 8 P a g e

9 Appendix C Humidex-Based Heat Response Guidelines for indoor work Note: Refer to the Humidex value from the Chart in Appendix A and modify it for a work clothing adjustment, if required. The guidelines assume regular summer clothes, including light shirt and pants, underwear and shoes. For an employee who must wear full cotton overalls over their clothes, 5º should be added to the Humidex value. Other clothing configurations should be prorated accordingly. For example, gloves, apron and protective sleeves or a lab coat over summer clothes would add 2º to the Humidex value. Humidex Number Response C supply water to workers on an as needed basis post Heat Stress Alert notice; C encourage workers to drink extra water; start recording hourly temperature and relative humidity post Heat Stress Warning notice; C notify workers that they are drinking extra water; ensure workers are trained to recognize symptoms provide 15 minutes relief per hour; C provide adequate cool (10-15 C ) water; at least 1 cup (240 ml) of water every 20 minutes workers with symptoms should seek medical attention provide 30 minutes relief per hour in addition to the C provisions listed previously; C if feasible provide 45 minutes relief per hour in addition to the provisions listed above. if a 75% relief period is not feasible then stop work until the Humidex is 42 C or less; 45 C or over stop work until the Humidex is 44 C or less 9 P a g e

10 Appendix D Field Temperature and / or Humidity Measurements Name(s): Date: Location Time Air Temp. ( o C) Relative Humidity (%) Humidex List of control 10 P a g e

11 Appendix E Signs and Symptoms of Heat Exposure (hyperthermia) Early Warnings Signs As Heat stress Worsens Headache Dizziness/Faintness Irritability/anger/mood change Fatigue Heavy Sweating Prickly heat (heat rash) Muscle cramps (especially after several days of exposure) Changes to breathing and pulse rate Dehydration Breathlessness (having trouble catching your breath A strong rapid pulse changes to a weak rapid pulse Sever head ache Sever muscle cramp Confusion Skin goes from feeling cold and clammy to hot and dry Severe dehydration Sweating may stop Exhaustion Coma and possible death 11 P a g e

12 Appendix F Personal Control Measures to reduced Heat Hydrate yourself. Water is crucial to helping the body adjust to high temperatures. The rate of water intake must equal the increased rate of water loss by perspiration to keep your body temperature normal. Avoid eating hot, heavy meals that increase your body temperature. Eat smaller but more frequent meals or snacks while working in hot environments Avoid alcohol or beverages with caffeine these make the body lose water and increase the risk of heat stress. Wear light clothing that permits the evaporation of sweat (ie. cotton clothing). Remember that your physical condition can reduce your ability to deal with the heat. Age, weight, fitness, health conditions (heart disease or high blood pressure), recent illness, or medications can all affect your ability to withstand high temperatures. Check with your doctor if your medication may affect your heat tolerance. Make healthy lifestyle choices (ie. body weight, fitness, diet, rest) 12 P a g e

13 Appendix G Rationale for Using Moderate Unacclimatized WBGT Category People come in all shapes and sizes, along with different fitness levels and tolerances to heat. Since the TLV is based on data derived from 20 year old males weighing an average of 154 lbs., "real" workers probably burn up more calories than the TLV light category assumes. Selecting the "moderate" work category will account to some extent for workers who are somewhat dehydrated, older (e.g. over 40), not male, and somewhat heavier than 154 lbs. Therefore, the Humidex-based heat response plan uses the ACGIH moderate unacclimatized workload category as the reference point for translating the WBGT into Humidex. 13 P a g e