Heat stroke, the most serious form of heat-related illness, happens when the body becomes unable to regulate its core temperature. Sweating stops and the body can no longer rid itself of excess heat. Signs include confusion, loss of consciousness, and seizures. Heat stroke is a medical emergency that may result in death! Call 911 immediately. The symptoms of a heat stroke include:

• Confusion
• Fainting
• Seizures
• Excessive sweating or red, hot, dry skin
• Very high body temperature

Heat exhaustion is the body’s response to loss of water and salt from heavy sweating. Signs include headache, nausea, dizziness, weakness, irritability, thirst, and heavy sweating.

Heat cramps are caused by the loss of body salts and fluid during sweating. Low salt levels in muscles cause painful cramps. Tired muscles—those used for performing the work—are usually the ones most affected by cramps. Cramps may occur during or after working hours.

Heat rash, also known as prickly heat, is skin irritation caused by sweat that does not evaporate from the skin. Heat rash is the most common problem in hot work environments.

There are a range of heat illnesses and they can affect anyone, regardless of age or physical condition, whether an individual is working indoors or outdoors.

Workers who are exposed to hot and humid conditions are at risk of heat-related illness. The risk of heat-related illness becomes greater as the weather gets hotter and more humid. This situation is particularly serious when hot weather arrives suddenly early in the season, before workers have had a chance to adapt to warm weather.

Indoor workplaces with hot conditions may include iron and steel foundries, brick-firing and ceramic plants, glass products facilities, electrical utilities (particularly boiler rooms), bakeries, commercial kitchens, laundries, chemical plants, material handling and distribution warehouses, and many other environments.

Outdoor workplaces with work in hot weather and direct sun, such as farm work, construction, oil and gas well operations, landscaping, emergency response operations, and hazardous waste site activities, also increase the risk of heat-related illness in exposed workers.

Under OSHA law, employers are responsible for providing workplaces free of known safety hazards. This includes protecting workers from extreme heat. An employer with workers exposed to high temperatures should establish a complete heat illness prevention program.

• Provide workers with water, rest and shade.
• Allow new or returning workers to gradually increase workloads and take more frequent breaks as they acclimatize or build a tolerance for working in the heat.
• Plan for emergencies and train workers on prevention.
• Monitor workers for signs of illness.

The heat index, which takes both temperature and humidity into account, is a useful tool for outdoor workers and employers (see Using the Heat Index: A Guide for Employers).

Wet Bulb Globe Temperature (WBGT) is the most accurate tool to measure heat hazards for outdoor workers. It takes temperature, humidity, wind speed, and radiant heat into account. The OSHA Technical Manual Heat Stress Chapter provides WBGT information and calculations, and the National Weather Service provides a prototype WBGT location tool and work/rest recommendations.

There is also the OSHA-NIOSH Heat Safety Tool. With the OSHA Heat Safety Tool, you have vital safety information available whenever and wherever you need it – right on your mobile phone.

OSHA does not have a specific standard that covers working in hot environments. Nonetheless, under the OSH Act, employers have a duty to protect workers from recognized serious hazards in the workplace, including heat-related hazards.

OSHA’s Occupational Exposure to Heat page explains what employers can do to keep workers safe and what workers need to know – including factors for heat illness, adapting to working in indoor and outdoor heat, protecting workers, recognizing symptoms, and first aid training. The page also includes resources for specific industries and OSHA workplace standards. Also look for heat illness educational and training materials on the Publications page.

Sunlight exposure is highest during the summer and between 10:00 a.m. and 4:00 p.m. Working outdoors during these times increases the chances of getting sunburned and other heat related illnesses. Requesting your employer or supervisor create work schedules that minimize sun exposure can be helpful. Some recommendations for scheduling include:

• Schedule breaks in the shade and allow workers to apply/reapply sunscreen throughout their shifts.
• Modify the work site by increasing the amount of shade available—for example, with tents, shelters, and cooling stations.
• Schedule outdoor tasks like mowing for early morning instead of noon, and rotate workers to reduce their sun exposure.
• Reduce the physical demands of the job. If heavy job tasks cannot be avoided, change work/rest cycles to increase the amount of rest time.

While it is good to stay hydrated, it is harmful to drink extreme amounts of water. You should generally not drink more than 12 quarts (48 cups) in a 24-hour period. If higher amounts of fluid replacement are needed due to prolonged work in high heat conditions, a more inclusive heat illness prevention program may be needed.

Typically, you should frequently drink small amounts of water before becoming thirsty to maintain good hydration. During moderate activity, in moderately hot conditions, you should drink about 1 cup every 15 to 20 minutes.