This document provides guidance on managing heat stress in the workplace. It discusses factors that contribute to heat stress like temperature, humidity, physical activity, and protective clothing. It recommends a 5 step process to manage heat stress: 1) training workers on prevention and symptoms, 2) selecting appropriate clothing, 3) dividing the workplace into heat exposure zones, 4) measuring temperature and humidity in each zone, and 5) using a heat stress calculator to assess risk and guide control measures like work-rest cycles and water intake. The goal is to help workers recognize symptoms early and regulate their workload to prevent heat-related illness.

1. Heat Stress
A guide to keeping your cool !!!!
November 28, 2022

2. Is Heat Stress a concern in your workplace?
 Has anyone been affected by heat in your workplace?
 Are fans needed to keep workers cool?
 Is work done in direct sunlight?
 Do workers wear extra clothing/protective equipment that can make
them hot?
 Have workers ever expressed concern about heat in the workplace?
 Chances are that you have answered YES to one or more of theses
questions. Actually “Heat Stress” is something most workplaces must
deal with – not just those who work in the hot sun or beside heat
producing machinery.

3. The purpose of this tool kit is to provide workplace parties with
strategies to:
 Recognize the symptoms
 Assessing the risk
 Putting together an effective control program
Purpose of this heat stress tool kit

4. Factors that Influence Heat Stress
 The heating and cooling of the body depends on the following factors:
 Air temperature
 Humidity
 Radiant heat load
 Physical activity
 Cooling
 Body adjustments

5.  There are two sources of heat exposure, the outside
environment and internal muscle activity. 80% of the muscle
activity is converted into body heat.
 High temperatures and high levels of physical activity create
heat stress.
 The body cools itself by evaporating sweat.
 High humidity hinders sweat from evaporating

6. Can you get used to heat?
 Yes
 The body will get used to working in a hot environment gradually
over time.
 This process of the body becoming more efficient at cooling itself
down is known as “acclimatization”
 The body redirects blood to the skin’s surface
 The heart becomes more efficient
 Sweating starts sooner and there is more of it
 Sweat contains less salt

7. Heat Rash, Sunburn and Heat Cramps

8. Causes, Symptoms and Treatment

9. 5 Steps to Managing Heat Stress
1. Training: measurements by themselves cannot guarantee a worker
protection from heat stress. It is essential that workers learn to
recognize the early signs and symptoms of heat stress and know
how to prevent them.
 If it is possible, workers need to be able to alter their pace of
work, take rest breaks, and drink in response to early symptoms
(a cup of water every 20 minutes.)
 The ideal heat stress response plan would let workers regulate
their own pace by “listening” to their bodies.

10. 2. Clothing;
 The heat stress action chart on next slide assumes workers are
wearing regular summer clothes
 If the workers wear a double layer of woven clothing add 50 of
Humidex to the workplace measurement
 Estimate the correction factor for other types of clothing/protective
equipment by comparing them with cotton overalls.
 If completely encapsulating suits are worn, heat stress should be
managed by monitoring vital signs as recommended

11. Humidex Action Recommended
Low
30 - 37
Post heat stress alerts
Drink water
Medium
38 - 39
Reduce physical activity
Drink a cup of water every 20 minutes
Moderate
40-41
Further reduce physical activity
Drink a cup of water every 15 – 20 minutes
High
42 - 44
Severely curtail physical activity
Ensure sufficient rest/recovery time
Drink a cup of water every 10 – 15 minutes
Extreme
45+
Hazardous to continue physical activity

12. 3. Select a measurement location
 Divide the workplace into zones that have similar heat
exposures
 Select a representative location in each zone where you can
take measurements.

13. 4. Measure workplace temperature and humidity.
5. Adjust for radiant heat
Look at heat stress
calculator on next slide

14. www.ohcow.on.ca/menuweb/heat_stress_calculator.htm

15. KEEP YOUR
COOL !!!