Heat Stress

Purpose
This program outlines how to assess the level of heat stress an individual may experience when working
outdoors and provides recommendations on types of controls that can be used to minimize the impact.
Scope
This program impacts all employees, students, volunteers and contractors (working under A-State
supervision), who work in hot environments.
Definitions
Acclimatization - The process or result of becoming accustomed to a new climate or to new conditions.
Heat Cramps - Caused by the body's depleted salt and water levels from excessive sweating resulting in
muscle cramps or spasms. They usually occur in the muscles used during work. The symptoms include
spastic contractions and pain in voluntary muscles mainly in the arms, legs, or torso.1
Heat Exhaustion - Often a precursor to heat stroke. It is often accompanied by elevated core body
temperatures around 38°C–39°C (100.4°F–102.2°F). Symptoms may include headache, nausea, dizziness,
fatigue, weakness, thirst, heavy sweating, irritability, and a decreased urine output.1
Heat Index - The heat index, also known as the apparent temperature, is what the temperature feels like
to the human body when relative humidity is combined with the air temperature. This has important
considerations for the human body's comfort. When the body gets too hot, it begins to perspire or
sweat to cool itself off. If the perspiration is not able to evaporate, the body cannot regulate its
temperature. Evaporation is a cooling process. When perspiration is evaporated off the body, it
effectively reduces the body's temperature. When the atmospheric moisture content (i.e. relative
humidity) is high, the rate of evaporation from the body decreases. In other words, the human body
feels warmer in humid conditions.2
Heat Strain - The body's physiological response to heat stress (e.g., sweating).1
Heat Stress – The net heat load to which a worker is exposed. Physical exertion, environmental factors,
and clothing worn all contribute to heat stress.1
Heat Stroke - The most serious heat-related illness and should be treated as a medical emergency. Heat
stroke occurs when the body becomes unable to adequately dissipate heat, losing the ability to regulate
core body temperature. The core body temperature rises rapidly, the sweating mechanism may fail, and
the body is unable to cool down. When heat stroke occurs, the body temperature can rise to 41oC
(106°F) or higher within 10 to 15 minutes. Thinking clearly, perception, planning, and other mental
processes become impaired, and the worker may be unable to recognize dangerous situations. Heat
stroke can cause death or permanent disability if emergency medical treatment is not given. Symptoms
include confusion, clumsiness, slurred speech, fainting/unconsciousness, hot dry skin, profuse sweating,
seizures, and high body temperature.1
Heat Syncope - Usually occurs after prolonged standing or sudden rising from a sitting or supine
position. Heat syncope symptoms include light-headedness, dizziness, and fainting. Dehydration and
inadequate acclimatization often contribute to heat syncope.1
Relative Humidity - The amount of water vapor present in air expressed as a percentage of the amount
needed for saturation at the same temperature.
Temperature - the degree or intensity of heat present in a substance or object, especially as expressed
according to a comparative scale and shown by a thermometer or perceived by touch.
Responsibilities
Environmental, Health and Safety
• Assist departments in implementation of this program.
Department/Supervisor/Principal Investigator
• Identify conditions in which heat stress may be a concern.
• Implement controls to reduce risk when heat stress is a concern.
• Train workers on what controls will be implemented and how to implement them.
• Provide guidance on the use of any PPE that is required.
• Schedule more physically demanding tasks during cooler times of the day.
Employees
• Be familiar with this program and the procedures associated with it.
• Report any hazards, incidents or injuries to their direct supervisor and EH&S.
• Follow all procedures as written or required for the work they are performing.
• Attend any training sessions deemed necessary to complete their work in a competent manner.
• Understand the signs and symptoms of heat related illnesses and watch for these symptoms in
co-workers.
Heat Stress Prevention
Heat stress can be induced by high temperatures, increased relative humidity, decreased air movement
or lack of shading from direct heat heavy workloads, the type of clothing being worn, etc. The goal of a
heat stress program is to keep the body temperature below 104° F. Consider the following control
examples that may reduce heat stress:
• Use air conditioning
• Increase ventilation
• Provide cooling fans
• Provide shade for outdoor work sites
• Acclimatize workers starting the first day of work in the heat.
• Re-acclimatize workers after extended absences
• Use work/rest schedules
• Limit strenuous work
• Train supervisors on heat stress prevention and how to identify symptoms
• Wear sun hats
• Light colored clothing
Some employees are more likely to have heat disorders than others. Younger employees and those
more physically fit are often less likely to have problems. Employees with heart, lung or kidney disease,
diabetes and those on medications are more likely to experience heat stress problems. Diet pills,
sedatives, tranquilizers, caffeinated drinks and excessive alcohol consumption can all exacerbate heat
stress effects.
Acclimatization is meant to reduce the impact of heat stress on the body. Employers should use a
structured program to help workers adapt to working in the heat. This means gradually introducing
normal work activities over the span of 7 to 14 days.
Heat Stress Treatment
Heat stress includes a series of conditions where the body is under stress from overheating. Supervisors
should be familiar with the signs and symptoms of these conditions which are provided below. They
should also be prepared to implement the first aid measures identified in the table to treat employees.
Condition Signs/Symptoms First Aid
Heat Strain
Painful muscle spasms
Pain usually in
abdomen, arms or legs
Rest in shady, cool area
Increase water intake
Wait a few hours to resume work
Heat Syncope
Brief fainting
Light Headed, dizziness
Headache
Nausea, vomiting
Increased pulse
Rest in shady, cool area
Increase water intake
Refrain from vigorous activity
Dehydration Fatigue
Reduce movement
Rest in shady, cool area
Increase water intake
Heat Exhaustion
Cool, moist skin
Heavy Sweating
Headache
Nausea, vomiting
Light headed, dizziness
Weakness, fatigue
Thirst
Irritability
Fast heartbeat
Rest in shady, cool area
Increase water intake
Loosen clothing
Cool with cold compresses/ ice packs
Take to Clinic or Emergency Room if symptoms
worsen or do not improve within 60 minute
Heat Stroke
Confusion or erratic
behavior
Fatigue
Seizures
Excessive sweating or
red, hot dry skin
Very high body
temperature
Medical Emergency!
Call 911 to summon ambulance
Move to shady, cool area
Loosen clothing
Fan air on, cold pack armpits
Wet with cool water
Provide fluids, preferably water
Stay with victim until help arrives
Resources
1 OSHA Technical Manual, Section III: Chapter 4 Heat Stress. OSHA Technical Manual (OTM) - Section III:
Chapter 4 | Occupational Safety and Health Administration
2
National Weather Service, National Oceanic and Atmospheric Administration. What is the heat index?
What is the heat index? (weather.gov