Best Practice - Working Safely in the Heat and Cold ' £ ||| l ’ I A Government of Alberta WORK SAFE ALBERTA Employment and Immiaratior Digitized by the Internet Archive in 2016 https://archive.org/details/bestpracticework00albe_0 Introduction 3 Section 1 : Exposure to Heat and Cold 4 The Body’s Response to Heat and Cold 4 Acclimatization 4 Heat 5 Other Factors 6 Section 2: Thermal comfort 8 What is it? 8 Human variability 8 Humidex 8 Wind Chill 9 Section 3: Human Performance 12 Health issues 12 Heat 12 Cold 13 Treatment and Prevention 16 Heat 16 First Aid For Heat Exposures 16 What and When to Drink 17 Cold 18 First Aid for Cold Exposures 1 9 Effects on Physical and Cognitive Performance 20 Section 4 - M easuring Hot and Cold Conditions 22 Heat 22 Comparing WBGT and Humidex 24 Wind Chill 25 Section 5: Case Studies and Weather Data 25 Case Studies: What would you do? 26 Seasonal Temperatures, Humidex and Wind Chill Data for Specific Locations 29 Section 6 - S tandards and guidelines 31 Exposure Limits 31 Heat : 31 Cold 48 Section 7: Controlling Exposure 53 Controlling Exposure 53 Heat 54 Cold 57 If y ou start to sweat 61 Appendix 1 : Weather Data for Selected Alberta Locations 63 Appendix 2: Humidex Based Response Plan (by OHCOW) 85 Appendix 3: Samples of Heat and Cold Stress Policies 89 Heat Stress 89 Cold Stress 91 Resources 88 GS006 - G eneral Safety 2 Updated August 2009 For many people, seeing that brilliant blue sky on a cold winter’s day or heading to the lake on a hot summer day can be some of the best benefits of living in Alberta. However, people who have to work on that extremely cold or hot day may feel very differently. The goal of this publication is to help you understand the health risks associated with working in extreme heat and cold situations, and to suggest reasonable solutions for workplaces. While many workplaces can benefit from this information, this publication is written primarily for people who work outdoors. Examples of these situations include road paving, construction, forestry, agriculture, ranching, oil and gas industry, greenhouse or horticultural work, power line maintenance, and outdoor municipal work. This guidance may also be helpful to workplaces that have hot indoor environments such as kitchens, bakeries, pizza parlours, steam presses, laundries, or dry cleaning businesses. Cold indoor workplaces include those that have walk-in freezers, meat processing, or cold storage facilities. This publication will help you to • Understand how your body reacts in cold or hot environments • Recognize when it is “too” cold or “too” hot • Know the health risks associated with working in these temperatures • Be able to understand weather information or take simple measurements • Know what steps to take to control the hazards of exposure. GS006 - G eneral Safety 3 Updated August 2009 Section 1 : E xposure to Heat and Cold The Body’s Response to Beat and Cold Your body works best when it has an internal “core” temperature of 37°C. 37°C might seem warm, but this is y our internal temperature (not the air temperature). This temperature is necessary for your vital organs to function normally. During a regular day, your body temperature may vary by about 1°C depending on the time of day, your level of physical activity and how you are feeling (emotional reactions). The body’s metabolic processes produce the right amount of heat you need when you digest your food and when you perform physical activity. Maintaining Balance When you work in extreme temperatures, your body has to adapt. To maintain a constant inner body temperature, the body must continually keep or gain heat in cold environments and lose heat in hot environments. To stay warm in cold environments, the body • Shivers - moving muscles help increase heat production, and • Reduces blood flow to the skin and extremities (hands and feet) to reduce heat loss from the surface. To stay cool in hot environments, the body • Sweats - e vaporating sweat cools the body, and • Increases blood flow to the skin - t o speed up the loss of heat from the skin (radiate away the excess heat) if t he outside air is cooler. By sweating, shivering, and changing the rate of blood flow, the body can adapt to a f airly wide range of temperatures. However, there are limits to what the body can adapt to and its ability to maintain its core temperature can fail. Acclimatization People can adapt to hotter temperatures through a p rocess called “acclimatization.” At the workplace, acclimatization is important because it a llows you to work more safely and efficiently. However, becoming acclimatized takes time. In cold conditions, the body can also adapt. There is some research that suggests that the body does not adapt as well to cold as it d oes to hot conditions. How the body adapts to cold is not as clearly understood. GS006 - G eneral Safety 4 Updated August 2009 When working in hot conditions, people need at least 4 t o 7 w orking days to become fully acclimatized, but the process may take up to three weeks. A s cheduled exposure is recommended. For example, doing physical work for less than a f ull working day on the first hot day and slowly increasing the time spent working over the next week. Each person must be monitored to ensure that he or she is adapting to working in the heat. Important... Each person is different. People who are in good health and physically fit tend to adjust faster and more easily. However, some individuals may not be able to fully acclimatize regardless of their health or physical condition. Always monitor yourself and your co-workers. People who are used to working in extreme temperatures can have an underlying condition (such as coming down with a f lu or cold) that changes how their body reacts to the temperature. Details about symptoms of exposure are in Section 3. Did you IlllOWlf As your hands get used to the cold, the body diverts more blood to them. Acclimatized workers at a f ish processing facility can fillet fish with their hands in near freezing water for long periods of time. A n on-accfimatized person would be in severe pain. Factors affecting how you feel How “hot” or “cold” you feel depends on 6 m ain factors: 1 . Air temperature - A ir temperature is what can be measured with a t hermometer. However, in situations where there is a l ot of radiant heat (see below for examples) it i s not always an accurate indication of how hot or cold you feel. 2. Other sources of heat (r adiant heat). These sources can include direct sunlight, machinery that generates heat, hot water, heaters or open flames, asphalt, etc. Over time on a h ot day, these sources can radiate heat into the air and add to the amount of heat you “feel”. 3. Relative humidity is the amount of moisture (water) in the air. The warmer the air, the more moisture it c an hold. High humidity makes people feel hotter because sweat does not evaporate off the skin (it i s the evaporation of sweat that makes you feel cooler). Cold air with high relative humidity “feels” colder than dry air at the same temperature. GS006 - G eneral Safety 5 Updated August 2009 Why? Because high humidity in cold weather increases the conduction (loss) of heat from the body to the surrounding air. 4. Moving air (speed) usually cools a p erson. This cooling provides relief in a h ot environment as long as the moving air is cooler than the person. In cold situations, air movement can create wind chill and make you feel much colder than the temperature may indicate. 5. Physical exertion (how hard you are working) also influences how hot or cold you feel. Moving around or working generates heat. When working on a very hot day, this movement increases your heat stress. 6. Clothing can help you stay warmer. However, when mist, rain or sweat is heavy enough to make your clothing wet, you feel colder as wet clothing loses its insulating properties. Other Factors A p erson’s general health also influences how well the person adapts to heat and cold. Those with extra weight often have trouble in both cold and hot situations due to the body having difficulty maintaining a g ood heat balance. Age (particularly for people about 45 years and older), poor general health, and a l ow level of fitness will make people more susceptible to feeling the extremes of heat and cold. Medical conditions can also increase how susceptible the body is to heat and cold. People with heart disease, high blood pressure, respiratory disease and uncontrolled diabetes may need to take special precautions. In addition, people with skin diseases and rashes may be more susceptible to heat, while people with Raynaud’s disease (also known as white finger or vibration disease) will be more susceptible to the cold. Substances - b oth prescription or otherwise - c an also have an impact on how people react to heat and cold. See Table 1 for some examples. GS006 - G eneral Safety 6 Updated August 2009 Table 1 : Substances that Can Affect a P erson’s Tolerance to Heat and Cold More Susceptible to Heat More Susceptible to Cold • Alcohol • Alcohol • • Amphetamines Amphetamines • Anaesthetics • Antidepressants • Anticholinergics (e.g. atropine) • Antithyroid drugs • Antidepressants • Cannabis (marijuana) • Cannabis (marijuana) • • Cocaine • Hypnotics Hypoglycaemic drugs • Hypnotics (e.g. barbiturates) Insulin • • Morphine Morphine • • Psychotropic drugs Organophosphates • Psychotropic drugs • Sympathetic and ganglion-blocking • agents Tranquilizers (Adapted From: Occupational Safety and Health Service, Department of Labour, New Zealand “Guidelines for the Management of Work in Extreme Temperature” http://www.osh.dol.qovt.nz/order/cataloque/pdf/temperat.pdf ) Tip! When ‘normal’ is your norm Thermal comfort is also very important. Ideally, air temperature should be kept within a range that most people find comfortable. The season, relative humidity, clothing and activity level of building occupants may factor into the comfort zone. In summer, temperatures of 23-28°C are recommended, while in the winter when relative humidity is closer to 30%, recommended temperatures are from 20-25°C. Please see the Indoor Air Quality Tool Kit published by Workplace Health and Safety, Government of Alberta for more information about indoor situations. http://emplovment.alberta.ca/documents/WHS/WHS-PUB qhOI 5.pdf GS006 - G eneral Safety 7 Updated August 2009 Section 2: Thermal comfort What is it? “Thermal comfort” refers to whether a p erson feels comfortable - not too hot nor too cold. Achieving thermal comfort is challenging because you need to account for the six factors (air temperature, radiant heat, relative humidity, moving air, physical exertion and clothing) described in Section 1 . Human variability Variability between people - d ifferent metabolic rates, levels of physical fitness, medical conditions (including medication), acclimatization, level of hydration, age, smoking, etc. makes achieving thermal comfort a challenge. These factors all affect how people perceive their comfort levels, even if t hey are doing the same work in the same environment. Humidex Canadian meteorologists created the humidex index in 1965. Humidex combines temperature and humidity readings into one number as a way of indicating how your body “ perceives ” t he combination of temperature and moisture in the air. It c an be a b etter measure of how stifling or stuffy the air “feels” versus temperature alone. It is expressed as a value, not as an actual temperature or “degrees”, because it i s an interpretation of how people might feel. Humidex becomes a significant factor when the index value is more than 30. The Weather Office of Environment Canada reports humidex when the value is more than 25. Humidex is intended for the general public and is not always appropriate to use as an indication of when work should be stopped. Heat-related illnesses depend on many other workplace factors such as wind speed or air movement, workload, radiant heat sources and a p erson's physical condition. Under certain workplace conditions, the humidex may serve as an indicator of discomfort resulting from occupational exposure to heat. For example, when humidity is high, but when workload, wind speed and radiant heat sources do not significantly contribute to the heat burden, humidex may be useful. If u sing humidex is appropriate for your work situation, Table 2 s hows how to determine humidex by using the air temperature and the relative humidity. GS006 - G eneral Safety 8 Updated August 2009 Table 2: Determining Humidex from Temperature and Relative Humidity Readings Source: Adapted from Environment Canada Wind Chili Wind chill is based on a mathematical calculation and represents how on a windy day the temperature would feel on your skin if t he wind were reduced to a walking pace of 4.8 km/h (3 mph). Like humidex, wind chill is expressed in temperature-like units but it is not an actual temperature. For example, the weather report will state that the outside temperature is -15°C with a wind chill of -30. This wind chill means that your face will feel as cold as it w ould on a calm day when the temperature is -30°C. Wind chill only affects objects that are warmer than the air temperature. Why does wind speed matter? On a calm day, your body is insulated because it w arms up a thin layer of air very close to your skin (called the "boundary layer"). Wind removes this protective layer. Warming up a new boundary layer takes energy. As the wind blows away each new boundary layer, you feel colder. The wind also contributes to evaporation of moisture from your skin or from damp clothing against the skin, which makes you feel colder by drawing more heat away from the body. In addition, wet skin loses heat much faster than dry skin (a fact that helps you stay cool in the summer, but also makes you colder in the winter). Wind Chill Hazards and Risk of Frostbite In most of Canada, wind chill is included in the forecast when it r eaches -25, as this is the point where frostbite becomes a risk. A w ind chill warning is issued by Environment Canada when conditions become hazardous. See Table 3 f or a l ist of wind chills and relative health risks. GS006 - G eneral Safety 9 Updated August 2009