Get the latest news, best practices and exclusive discounts

Water. Rest. Shade – Understanding Heat Index

F Marie Athey OHST

Posted by:

F Marie Athey OHST | September 11, 2013 | Comments Off on Water. Rest. Shade – Understanding Heat Index

OSHA’s focused heat awareness campaign put emphasis on getting work done safely with “Water. Rest. Shade.” The campaign focused on implementing a heat illness prevention program based on heat index. Heat illnesses are preventable and need not result to workplace fatalities according to OSHA. This is also the opinion of many employers and safety professionals who also advocate for prevention injury programs regarding heat illness.

What causes heat illnesses? Workers get sick from heat due to working in hot temperatures not only outside but where exposed indoors to high heat processes. Work conditions combined with the heat generated by their body due to physical labor will result in heat exhaustion or heat stroke. If employers implement preventive measures based on heat index values, along with breaks, change of shift to cooler times of the day, and supply plenty of fluids,  incidences of heat-related illness will be minimized, even eradicated completely.

Reading the Index

The U.S. National Oceanographic and Atmospheric Administration (NOAA) developed the heat index system. The index combines both air temperature and relative humidity into a single value that reflects how hot the weather is in Fahrenheit. The higher the heat index the greater the heat illness risks will be for workers.  NOAA releases heat advisories as the weather shoots up.

The index is color-coded depending on risk levels. When the index is at less than 91 degrees, it will appear in yellow, which means the risk level is lower and employers and workers should take caution. This also calls for basic heat safety and planning. When the index falls between 91 degrees and 103, the value’s corresponding color equivalent is yellow-orange. See the rest of the color-coding scheme, risk levels and protective recommendations based on the heat index below:



Note that as humidity increases, sweat doesn’t evaporate as quickly and you feel hotter. Low humidity, on the other hand, causes sweat to evaporate quickly which can result in dehydration.

What can be done?

OSHA recommends the use of the index in planning and training to prevent heat-related illnesses. OSHA also advises the following heat-related illness preventive measures for employers:

1.       Gather necessary hot weather supplies. Stock up on hot weather supplies like water, water containers, first aid kits, and shade devices. Assign a person who will make sure that quantities of the supply are sufficient for employees.

2.       Create an emergency action plan. Design an emergency action plan and appoint people who will take charge of implementing it.

3.       Watch out for heat advisories and make sure workers are informed of them. Keep your staff posted of weather updates and heat advisories from the National Weather Service (NWS) or NOAA. Make sure information is disseminated at outdoor work sites.

4.       Train workers prior to project commencement. Train workers on risk factors for heat-related illnesses, recognizing the symptoms of heat-related illnesses, addressing such symptoms and preventing illnesses.

5.       Develop a work/rest schedule. Plan a work and rest schedule for outdoor workers especially when the weather is too hot. Rest periods can be spent by workers doing some light work like sorting out some paperwork or attending a meeting.

6.       Acclimatize workers to the heat conditions. Develop a heat illness awareness program for workers. This is accomplished by increasing the employee’s workload at a moderate pace from 50 to 100 percent within a week. However, be aware that some workers may take up to two weeks to get used to the heat conditions.

Short URL:

Comments are closed.