Appendix C: Adverse Weather Conditions | Safety Guidelines for the Film and Television Industry in Ontario

• ISBN: 978-1-4249-9952-1
• Issued: January 1997
• Revised: June 2009
• Content last reviewed: August 2010
• PDF Version [ 1.15 Mb / 198 pages | Download Adobe Reader ]

Adverse Weather Conditions

This information applies to any four-hour period.
Warm-up breaks are assumed to provide 10 minutes in a warm environment.
These guidelines apply to workers wearing dry clothing.

Sunny sky Air Temperature		No noticeable wind		Wind 8 km ⁄ h (10 mph)		Wind 16 km ⁄ h (10 mph)		Wind 24 km ⁄ h (15 mph)		Wind 32 km ⁄ h (20 mph)
°C below zero	°F below zero	Max. work period	Number of work breaks	Max. work period	Number of work breaks	Max. work period	Number of work breaks	Max. work period	Number of work breaks	Max. work period	Number of work breaks
26 to 28	15 to 19	normal breaks	1	75 minutes	2	55 minutes	3	40 minutes	4	40 minutes	4
29 to 31	20 to 24	normal breaks	1	75 minutes	2	55 minutes	3	40 minutes	4	30 minutes	5
32 to 34	25 to 29	75 minutes	2	55 minutes	3	40 minutes	4	30 minutes	5	Non-emergency work should stop
35 to 37	30 to 34	55 minutes	3	40 minutes	4	30 minutes	5	Non-emergency work should stop
38 to 39	35 to 39	40 minutes	4	30 minutes	5	Non-emergency work should stop
40 to 42	40 to 44	30 minutes	5	Non-emergency work should stop
43 and below	45 and below	Non-emergency work should stop

∗ all temperatures are approximate

Apply the schedule one step lower for work with limited physical activity. For example, at −35°C (−35°F) with no noticeable wind, a worker with a job requiring little physical movement should have a maximum work period of 40 minutes with four breaks in a four-hour period.

If reliable weather reports are not available, use the following as a guide to estimate wind velocity:

• An 8 km/h (5 mph) wind will move a light flag
• A 16 km/h (10 mph) wind will fully extend the flag
• A 24 km/hr (15 mph) wind will raise a newspaper sheet
• A 32 km/h (20 mph) wind will produce blowing and drifting snow

If only the Wind Chill Factor (in watts per square metre) or Equivalent Temperature are available, a rough guide for applying them, rather than the temperature and wind velocity factors above, would be:

• Special warm-up breaks should be initiated at a wind chill of about 1750 (Equivalent Temperature of −32°C)
• All non-emergency work should stop at or before a wind chill of 2250 (Equivalent Temperature of −51°C)

If wind speeds are higher than those identified in the chart, a wind chill value of 2250 (or Equivalent Temperature of −51°C) should be used to determine the point at which all non-emergency work should stop.

Reference:

Work Warm-up Schedule for Outdoor Activities; Occupational Health and Safety Division Saskatchewan Department of Labour

Wind Chill Calculation Chart

Wind chill for temperatures from +5 to −20 °C

Tair (°C) V10 (km⁄h)	5	0	−5	−10	−15	−20
5	4	−2	−7	−13	−19	−24
10	3	−3	−9	−15	−21	−27
15	2	−4	−11	−17	−23	−29
20	1	−5	−12	−18	−24	−30
25	1	−6	−12	−19	−25	−32
30	0	−6	−13	−20	−26	−33
35	0	−7	−14	−20	−27	−33
40	−1	−7	−14	−21	−27	−34
45	−1	−8	−15	−21	−28	−35
50	−1	−8	−15	−22	−29	−35
55	−2	−8	−15	−22	−29	−36
60	−2	−9	−16	−23	−30	−36
65	−2	−9	−16	−23	−30	−37
70	−2	−9	−16	−23	−30	−37
75	−3	−10	−17	−24	−31	−38
80	−3	−910	−17	−24	−31	−38

Wind chill for temperatures from −25 to −50 °C

Tair (°C) V10 (km ⁄h)	−25	−30	−35	−40	−45	−50
5	−30	−36	−41	−47	−53	−58
10	−33	−39	−45	−51	−57	−58
15	−35	−41	−48	−54	−60	−66
20	−37	−43	−49	−56	−62	−68
25	−38	−44	−51	−57	−64	−70
30	−39	−46	−52	−59	−65	−72
35	−40	−47	−53	−60	−66	−73
40	−41	−48	−54	−61	−68	−74
45	−42	−48	−55	−62	−69	−75
50	−42	−49	−56	−63	−69	−76
55	−43	−50	−57	−63	−70	−77
60	−43	−50	−57	−64	−71	−78
65	−44	−51	−58	−65	−72	−79
70	−44	−51	−58	−65	−72	−80
75	−45	−52	−59	−66	−73	−80
80	−45	−52	−60	−67	−74	−81

Where
^Tair = Actual Air Temperature in °C
V₁₀ = Wind Speed at 10 metres in Km⁄h (as in weather observations)

Notes:

1. For a given combination of temperature and wind speed, the wind chill index corresponds roughly to the temperature that one would feel in a very light wind. For example, a temperature of −25°C and a wind speed of 20 km⁄h give a wind chill index of −37. This means that, with a wind of 20 km⁄ h and a temperature of −25°C, one would feel as if it were −37°C in a very light wind.


2. Wind chill does not affect objects and does not lower the actual temperature. It only describes how a human being would feel in the wind at the ambient temperature.


3. The wind chill index does not take into account the effect of sunshine. Bright sunshine may reduce the effect of wind chill (make it feel warmer) by 6 to 10 units.

Back to first table
Back to second table

Frostbite Guide

Low risk of frostbite for most people
Increasing risk of frostbite for most people within 30 minutes of exposure
High risk of most people in 5 to 10 minutes of exposure
High risk for most people in 2 to 5 minutes of exposure
High risk for most people in 2 minutes of exposure or less

Wind Chill Hazards

Check the wind chill before you go outdoors in the winter, and make sure you are well prepared for the weather. Even moderate wind chill values can be dangerous if you are outside for long periods.

Note: The guidelines on frostbite in the table below apply to healthy adults.

Wind Chill Hazards and Risk of Frostbite

Wind Chill	Risk of frostbite	Health Concern	What to do
0 to −9	Low	– Slight increase in discomfort	– Dress warmly, with the outside temperature in mind.
−10 to −27	Low	– Uncomfortable – Risk of hypothermia if outside for long periods without adequate protection	– Dress in layers of warm clothing, with an outer layer that is wind-resistant. – Wear a hat, mittens and scarf. – Keep active.
−28 to −39	Increasing risk: exposed skin can freeze in 10 to 30 minutes	– Check face and extremities (fingers, toes, ears and nose) for numbness or whiteness – Risk of hypothermia if outside for long periods without adequate protection	– Dress in layers of warm clothing, with an outer layer that is wind-resistant. – Cover exposed skin: wear a hat, mittens and a scarf, neck tube or face mask. – Keep active.
−40 to −47	High risk: exposed skin can freeze in 5 to 10 minutes*	– Check face and extremities (fingers, toes, ears and nose) for numbness or whiteness (frostbite) – Risk of hypothermia if outside for long periods without adequate protection	– Dress in layers of warm clothing, with an outer layer that is wind-resistant. – Cover all exposed skin: wear a hat, mittens and a scarf, neck tube or face mask. – Keep active.
Warning Level** −48 to −54	High risk: exposed skin can freeze in 2 to 5 minutes*	– Check face and extremities frequently for numbness or whiteness (frostbite) – Serious risk of hypothermia if outside for long periods	– Be careful. Dress very warmly in layers of clothing, with an outer layer that is wind-resistant. – Cover all exposed skin: wear a hat, mittens and a scarf, neck tube or face mask. – Be ready to cut short or cancel outdoor activities. – Keep active.
−55 and colder	High risk: exposed skin can freeze in less than 2 minutes	Danger! – Outdoor conditions are hazardous	– Stay indoors.

* In sustained winds over 50 km/h, frostbite can occur faster than indicated.

**In parts of the country with a milder climate (such as southern Ontario and the Atlantic provinces except Labrador), a wind chill warning is issued at about −35°C. Further north, people have grown more accustomed to the cold, and have adapted to the more severe conditions. Because of this, Environment Canada issues warnings at progressively colder wind chill values as you move north. Most of Canada hears a warning at about −45. Residents of the Arctic, northern Manitoba and northern Quebec are warned at about −55 °C., and those of the high Arctic, at about −55 °C.

Reference:

Wind Chill Calculator
Environment Canada Wind Chill Program

Note from MOL:

It should be noted that wetness increases heat loss and that sweating should be avoided by dressing in layers and that wet clothing should be replaced by dry clothing.

Heat Stress

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Produced by Specialized Professional Services
Reviewed: June 2007
Revised: May 2009
ISBN: 978-1-4249-9945-3

Legal Requirements:

Employers have a duty under section 25(2)(h) of the Occupational Health and Safety Act to take every precaution reasonable in the circumstances for the protection of a worker. This includes developing hot environment policies and procedures to protect workers in hot environments due to hot processes or hot weather.

For compliance purposes, the Ministry of Labour recommends the Threshold Limit Values (TLVs) for Heat Stress and Heat Strain published by the American Conference of Governmental Industrial Hygienists (ACGIH) . These values are based on preventing unacclimatized workers' core body temperatures from rising above 38°C.

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This Guideline is intended to assist employers, workers and other workplace parties in understanding heat stress, and in developing and implementing policies to prevent heat stress-related illness in the workplace.

What Is Heat Stress?

Working or playing where it is hot puts stress on your 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 heat-related illness, disability and even death.

This can happen to anybody-even the young and fit. In Ontario, heat stress is usually a concern during the summer. This is especially true early in the season, when people are not used to the heat.

Heat exposure may occur in many workplaces. Furnaces, bakeries, smelters, foundries and heavy equipment are significant sources of heat inside workplaces. For outdoor workers, direct sunlight is usually the main source of heat. In mines, geothermal gradients and equipment contribute to heat exposure. Humidity in workplaces also contributes to heat stress.

How We Cope With Heat

Your body is always generating heat and passing it to the environment. The harder your body is working, the more heat it has to lose. When the environment is hot or humid or has a source of radiant heat (for example, a furnace or the sun), your body must work harder to get rid of its heat.

If the air is moving (for example, from fans) and it is cooler than your body, it is easier for your body to pass heat to the environment.

Workers on medications or with pre-existing medical conditions may be more susceptible to heat stress. These workers should speak to their personal physicians about work in hot environments.

Heat Stress-Related Disorders

A summary of heat stress-related disorders, causes, symptoms, treatment and prevention is presented in the table below.

	Cause	Symptoms	Treatment	Prevention
Heat Rash	Hot humid environment; plugged sweat glands.	Red bumpy rash with severe itching.	Change into dry clothes and avoid hot environments. Rinse skin with cool water.	Wash regularly to keep skin clean and dry.
Heat Cramps	Heavy sweating from strenuous physical activity drains a person's body of fluid and salt, which cannot be replaced just by drinking water. Cramps occur from salt imbalance resulting from failure to replace salt lost from heavy sweating.	Painful cramps commonly in the most worked muscles (arms, legs or stomach) which occur suddenly at work or later at home. Heat cramps are serious because they can be a warning of other more dangerous heat-induced illnesses.	Move to a cool area; loosen clothing, gently massage and stretch affected muscles and drink cool salted water (¼ to ½ tsp. salt in 1 litre of water) or balanced commercial fluid electrolyte replacement beverage. If the cramps are severe or don't go away after salt and fluid replacement, seek medical aid. Salt tablets are not recommended.	Reduce activity levels and⁄or heat exposure. Drink fluids regularly. Workers should check on each other to help spot the symptoms that often precede heat stroke.
Fainting	Fluid loss and inadequate water intake.	Sudden fainting after at least two hours of work; cool moist skin; weak pulse.	Get Medical attention. Assess need for CPR. Move to a cool area; loosen clothing; make person lie down; and if the person is conscious, offer sips of cool water. Fainting may also be due to other illnesses.	Reduce activity levels and⁄or heat exposure. Drink fluids regularly. Workers should check on each other to help spot the symptoms that often precede heat stroke.
Heat Exhaustion	Fluid loss and inadequate salt and water intake causes a person's body's cooling system to start to break down.	Heavy sweating; cool moist skin; body temperature over 38°C; weak pulse; normal or low blood pressure; person is tired and weak, and has nausea and vomiting; is very thirsty; or is panting or breathing rapidly; vision may be blurred.	Get Medical Attention. This condition can lead to heat stroke, which can kill. Move the person to a cool shaded area; loosen or remove excess clothing; provide cool water to drink; fan and spray with cool water.	Reduce activity levels and⁄or heat exposure. Drink fluids regularly. Workers should check on each other to help spot the symptoms that often precede heat stroke.
Heat Stroke	If a person's body has used up all its water and salt reserves, it will stop sweating. This can cause body temperature to rise. Heat stroke may develop suddenly or may follow from heat exhaustion.	High body temperature (over 41°C) and any one of the following: the person is weak, confused, upset or acting strangely; has hot, dry, red skin; a fast pulse; headache or dizziness. In later stages, a person may pass out and have convulsions.	Call Ambulance. This condition can kill a person quickly. Remove excess clothing; fan and spray the person with cool water; offer sips of cool water if the person is conscious.	Reduce activity levels and/or heat exposure. Drink fluids regularly. Workers should check on each other to help spot the symptoms that often precede heat stroke.

Controlling Heat Stress

Acclimatization

The longer you work in a hot environment, the better your body becomes at adjusting to the heat. This is called “acclimatization”. If you are ill or away from work for a week or so you can lose your acclimatization.

To become acclimatized, the following may be considered:

1. If you are experienced on the job, limit your time in hot working conditions to 50 per cent of the shift on the first day, 60 per cent of the shift on the second day, and 80 per cent of the shift on the third day. You can work a full shift the fourth day.
   
   If you are not experienced on the job (if you are, for example, a new employee), you should start off spending 20 per cent of the time in hot working conditions on the first day and increase your time by 20 per cent each subsequent day.
2. Instead of reducing the exposure times to the job in a hot environment, you can become acclimatized by gradually increasing the physical demands of the job over a week or two.

If you have health problems or are not in good physical condition, you may need longer periods of acclimatization. Hot spells in Ontario seldom last long enough to allow acclimatization. However, exposure to workplace heat sources may permit acclimatization.

When there is a potential exposure to heat stress, control measures must be taken to prevent heat exposure in the workplace. These include engineering controls, administrative controls and protective clothing. Selection of appropriate workplace controls will vary, depending on the type of workplace and other factors. Some measures may include:

• Reduce physical demands of work task through mechanical assistance (hoists, lift-tables, etc.).
• Control the heat at its source through the use of insulating and reflective barriers (e.g. insulate furnace walls).
• Exhaust hot air and steam produced by operations.
• Reduce the temperature and humidity through air cooling.
• Provide cool, shaded work areas.
• Provide air-conditioned rest areas.
• Increase air movement if temperature is less than 35°C (e.g. use of fans).

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.
• Provide cool drinking water near workers and remind them to drink a cup about every 20 minutes.
• 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 physicians.
• First Aid responders and an emergency response plan should be in place in the event of a heat related illness.
• Investigate any heat-related incidents.

Protective Clothing

• Light summer clothing should be worn to allow free air movement and sweat evaporation.
• Outdoors, 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 such as heat strain (physiological) monitoring.

Managing Heat Stress From Process Heat

For an environment that is hot primarily due to process heat (furnaces, bakeries, smelters, etc.), the employer should follow the guidance of the American Conference of Governmental Industrial Hygienists (ACGIH) as outlined in its booklet and documentation for the recommended Threshold Limit Value (TLVs), and set up a heat stress control plan in consultation with the workplace's joint health and safety committee or worker health and safety representative.

Further information on the ACGIH TLVs, and on the development of heat stress control plans, may be found at the following websites:

• American Conference of Governmental Industrial Hygienists (ACGIH)
• U.S.Occupational Safety and Health Administration (OSHA)

Managing Heat Stress Induced By Hot Weather

Most workplaces don't have “hot processes” but working in hot weather can pose health risks to their workers. For hot work environments due to hot weather, a hot weather plan is appropriate. A hot weather plan is a simplified heat stress control plan. A hot weather plan should establish the implementation criteria, or “triggers”, to put the plan into effect. The criteria may include weather /environmental indicator triggers such as:

• Humidex reaching or exceeding 35;
• Environment Canada Humidex advisory (air temperature exceeding 30°C and Humidex exceeding 40);
• Environment Canada weather reports;
• Heat waves (three or more days of temperatures of 32°C or more); and⁄or
• Ontario Ministry of the Environment smog alert.

Generally, plans related to hot weather should be in place between May 1 and September 30 of each year.

The following websites have information on Humidex, weather reports and smog alerts:

• Environment Canada
• Environment Canada Fact Sheet: Summer Severe Weather
• Environment Canada Humidex Calculator
• Environment Canada Weather Office
• Air Quality Ontario Smog Advisories

Other Resources

Additional information on methods to monitor and manage workplace heat exposures may be found in the following resources:

WSIB Prevent Heat Stress

This website provides links to information and tools on heat stress awareness, monitoring and control measures.

A link is given to access the “Heat Stress Awareness Toolkit” which includes a guidebook, a poster, and a tool to determine Humidex guidelines. This toolkit was developed by the members of the Occupational Health and Safety Council of Ontario (OHSCO).

Prevention Dynamics Ontario’s Virtual Health and Safety Portal

This website provides links to health and safety information, training materials, and consulting services offered by Ontario’s Health and Safety Associations and Partners.

Note: Links to external websites are offered for the convenience of users in accessing related information. These links do not constitute an endorsement of the websites or their contents and the Ministry of Labour takes no responsibility for the views, contents or accuracy of the information presented by an external website.

Remember that while complying with occupational health and safety laws, you are also required to comply with applicable environmental laws.

For further information or assistance, please contact your local office of the Ministry of Labour.