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College of Food, Agricultural, and Environmental Sciences

Heat Stress Illness

Working in hot weather conditions is a setting common for individuals in agricultural operations or research. Working in extreme hot temperatures can overwhelm the body’s internal temperature control system. A heat stress injury occurs when the body cannot regulate its temperature. If the body is working correctly, it is self-cooled by perspiration. When the body's temperature rises faster than it can cool itself, the core temperature begins to rise quickly and heat stress injuries result. Heat stress can contribute to adverse health effects which range in severity from discomfort to death.

In April of 2022, Outdoor and Indoor Heat-Related Hazards became an OSHA National Emphasis Program. The program encourages interventions by employers to prevent illnesses and deaths among workers during high heat conditions. Early interventions include, but are not limited to, implementing water, rest, shade, training, and acclimatization procedures for new or returning employees.

Factors associated with heat related illness include:
- Outdoor temperature
- Length of sun exposure
- Dehydration
- Workloads and speed of work
- Age
- Preexisting health conditions
- Acclimatization (how new the person is to the heat and the job)

Heat Stress Illness includes:

Heat stroke – This is the most serious heat related effect. Heat stroke occurs when the body temperature increases above 104° F.  Signs and symptoms: confusion, loss of consciousness, seizures, and lack of perspiration. This condition must be treated as a medical emergency and the employee must receive immediate medical attention.

Heat exhaustion – Signs and symptoms:  headache, nausea, dizziness, weakness, irritability, confusion, thirst, heavy perspiration and a body temperature greater than 100.4° F.

Heat cramps – Signs and symptoms: muscle pains usually caused by the loss of body salts/fluids, this can happen later as well. Employees should replace fluid loss by drinking water and/or carbohydrate-electrolyte liquids every 15 to 20 minutes.

Heat rash – Heat rash is caused by excessive perspiration and looks like a red cluster of pimples or small blisters.

Dehydration – Dehydration is a major factor in most heat disorders. Signs and symptoms: increasing thirst, dry mouth, weakness or light-headedness, darkening of the urine or a decrease in urination.

Employees experiencing heat stress illness should be moved to a cool area, given fluids to drink and given cold compresses for their head, face and neck.

How hot is too hot? Occupational Heat exposure can be based on the Heat Index. The heat index is what the temperature feels like to the human body when relative humidity is combined with the air temperature. Outdoor workers should have a plan to reduce the chances of heat stress illness when the day's Heat Index is 86°F or higher. Refer to the NOAA Heat Index Chart to make work interventions and adjustments.

Guidelines to prevent heat stress illness:
- Strenuous work should be scheduled for the coolest time of day (early morning or evening).
- Dress lightly - lightweight, light-colored clothing reflects heat and sunlight.
- Take multiple short breaks in a shaded area or controlled environment, throughout the day.
- Stay Hydrated – Drink plenty of fluids before, during, and after strenuous activities. Cold fluids can also help cool the body. Hydrating the body should start 24 hours before activities in higher temperatures.
- Use extreme caution when working around equipment or machines that will give off additional heat during operations.
- Provide ventilation to enclosed work locations with limited airflow.

OSU Environmental Health and Safety has developed a Heat and Cold Stress Safety Program to
minimize the effects of heat stress on Ohio State University employees. This program contains the procedures and practices for safely working in temperature extremes. Our CFAES Safety Team can also conduct exposure assessments and assist departments with the development of procedures to minimize the adverse effects of heat stress with employees during agricultural operations and field research.

NOAA Heat Index Chart
OSU Heat and Cold Stress Program
OSU EHS Safety Brief: Heat Stress Poster
OSHA Heat Exposure
OSHA Heat Stress Work Poster
AgriSafe: Heat Related Illnesses
Ohio BWC Safety Bulletin - Heat Stress
NIOSH Heat Index Safety Tool App

Employee Training
The College of Food, Agricultural and Environmental Sciences follows a training program that can be accessed via OSU Environmental Health and Safety website. ( A Heat and Cold Stress module is available for faculty, staff and students. Additional training specific to equipment, processes, or locations may be required by the supervisor.

OSU Employee On-line Training:

1) Click on this link -
2) Cick on the Occupational Health & Safety content area.

3) Scroll down to locate the Heat & Cold Stress training course and click on "Take this Course".
4) Sign in using your login (last name.###).
5) At the end of the on-line training you will be prompted to take the quiz.
6) Once training has been completed, a list your training sessions will be listed under “My Training”.

If you have any questions regarding Heat Stress Illness, please contact Kent McGuire at or 292-0588. You may also contact the OSU Environmental Health and Safety Office online at or by phone at (614) 292-1284.


Reviewed / Updated: 5/19/22 K. McGuire