Heat Science

Daily Heat Stress Indicators

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It is important for employers to protect their workers from heat-related illnesses and injuries when working in high heat environments. If your occupation involves working in high heat environments, it’s important to be aware of environmental conditions and take steps to prepare for steps outlined in the current OSHA National Emphasis Program on Outdoor and Indoor Heat Hazards.

Here are some steps you can take to get ready for the OSHA NEP and the treat of heat-related illness:

  1. Learn about the OSHA NEP. Read and understand the OSHA objective to develop a national heat standard, which outlines the requirements for employers to protect their workers from heat-related illnesses and injuries. You can find this information on the OSHA website at https://www.osha.gov/enforcement/directives/cpl-03-00-024  or check with your employer’s Human Resource or Safety Departments
  2. Become aware of the signs and symptoms of heat-related illnesses: Learn the signs and symptoms of heat exhaustion and heat stroke, which can include fatigue, nausea, headache, dizziness, and confusion. If you experience any of these symptoms, it’s important to seek medical attention immediately.
  3. Stay hydrated: Drink plenty of fluids.  A proper regimen of water and Sqwincher electrolyte replenishment, before, during, and after working in high heat environments to help prevent and/or recover from dehydration. Avoid drinks that contain caffeine, alcohol, or excessive sugar.
  4. Wear appropriate clothing: Wear light-colored, loose-fitting clothing that covers as much skin as possible. Choose fabrics that are breathable and can wick moisture away from the skin.
  5. Take breaks and rest in a cool area: Take frequent breaks and rest in a cool area to help regulate your body temperature. Use fans or air conditioning, if available.
  6. Follow your employer’s heat safety plan: Your employer should have a heat safety plan in place that includes measures such as providing water and rest breaks, monitoring workers for signs of heat-related illness, and adjusting work schedules to avoid working during the hottest parts of the day. Follow these measures and report concerns to your supervisor.

By following these steps, and taking advantage of the tools identified and recommended here, you can help protect yourself and others from heat-related illnesses and injuries in accordance with OSHA recommended guidelines.

Recommended Downloads and Sources

The Centers for Disease Control and Prevention’s
National Institute for Occupational Safety and Health (NIOSH)

OSHA-NIOSH Heat Safety Tool App

Exposure to full sunshine can increase heat index values by up to 15°F.

The OSHA-NIOSH Heat Safety Tool app provides more comprehensive data at your fingertips, including:

• An interactive, hourly forecast of heat index values, risk levels, and recommendations for planning outdoor work activities

• Location, temperature, and humidity controls you can edit to calculate for different conditions

• Signs and symptoms and first aid for heat-related illnesses

Workers at risk of heat stress include those in hot environments such as firefighters, bakery workers, farmers, construction workers, miners, boiler room workers, factory workers, and others.

Workers at greater risk of heat-related illness are 65 years of age or older, overweight, and/or have heart disease or high blood pressure. More about risk factors: Heat Stress Risk Factors

Train workers to understand what heat stress is, how it affects their health and safety, and how it can be prevented.

NIOSH Training Tips NIOSH Heat Stress Podcast

Heat stress can result in heat stroke, heat exhaustion, heat cramps, or heat rashes.

OSHA ® Quick Card:
Protecting Workers from Heat Stress

New employees are at highest risk for heat illness. Acclimatization is crucial to heat tolerance.

Acclimatization

OSHA® Science of Heat Hazard Assessment

Heat Index

Heat Index (HI) uses 2 factors—temperature and relative humidity—to calculate an adjusted temperature in shady, slightly windy conditions.

Wet Bulb Global Temperature (WBGT) uses 4 factors—humidity, air movement, radiant heat, and temperature—and is recommended by OSHA® to be more accurate in determining if a heat hazard is present.

Environment + Clothing + Workload = Heat Hazard

The science of heat hazard assessment

Environmental factors (e.g., humidity, wind, temperature, and radiant heat), clothing, and workload (i.e., metabolic rate) are considered when determining if there is a heat hazard present in an indoor or outdoor workplace. After the WBGT is measured, clothing adjustment factor added, and workload translated into metabolic rate; use the ACGIH TLV & Action Limit table to determine the risk for exposure to heat stress above the AL for un-acclimatized workers or the TLV for acclimatized workers.

1 Determine WBGT

Calculate the WBGT either using a meter or Weather Data. Various formulae are available based on workplace location and cloud cover.

2 Clothing Adjustment Factor

Identify the ACGIH Clothing Adjustment Factor (CAF) based on the clothing workers are wearing. Add the CAF to the WBGT to determine WBGTeff.

3 Determine metabolic Work rate

The ACGIH metabolic work rates represent impacts to the body core temperature from the heat produced internally as exertion increases.

4 Determine threshold limit value (tav) or action limit (AL)

The TLV is the temperature at which there is a heat hazard present for an acclimatized worker and the AL is the temperature at which there is a heat hazard present for a non-acclimatized worker.

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