The dog days of summer are upon us, but what does that actually mean? This phrase refers to the hottest, most uncomfortable part of the summer, usually ranging from July through August. In ancient times, the return of Sirius (the Dog Star), which is the brightest star in the night sky, would be a forerunner of the hottest phase of the summer. For many, the month of August may mean the end of summer vacation is approaching, but for outdoor workers, these dog days mean dangerously hot temperatures. Extreme heat causes more deaths than any other weather-related hazard; each year more than 65,000 people seek medical treatment for extreme heat exposure. According to OSHA, in 2014 there were 2,630 workers who suffered from heat-related illness, and 18 died from heat stroke and related causes on the job. Heat-related illnesses are not the only concern; work-related exposure to heat can also result in reduced productivity and growing risk of injuries, such as those caused by sweaty palms, fogged-up safety glasses, and cognitive impairment.

Last year, NIOSH published Criteria for a Recommended Standard: Occupational Exposure to Heat and Hot Environments. This technical document provides safety professionals and employers an evaluation of the scientific data on heat stress and NIOSH recommendations. This summer, NIOSH and OSHA released a redesigned OSHA-NIOSH Heat Safety Tool app. The app uses the device’s geolocation capabilities to pull temperature and humidity data from National Oceanic and Atmospheric Administration satellites to determine the heat index. The app shows the current risk level (minimal, low, moderate, high, or extreme) and forecasts the hourly heat index throughout the entire workday, giving employers information they can use to adjust the work environment as needed to protect workers.

The heat index is a measure of how hot it feels when relative humidity is taken into account along with the actual air temperature. Both the heat index and wet bulb globe temperature are used to measure environmental temperature. NIOSH recommends the use of wet bulb globe temperature to determine the recommended exposure limits (RELs) and the recommended alert limits (RALs) in hot environments. However, many workers and small businesses will not have access to the resources necessary to determine wet bulb globe temperature.  In these situations, using the heat index is a viable alternative. While the literature provides plenty of evidence regarding the accuracy of wet bulb globe temperature and common usage in industrial settings, the simplicity of the heat index makes it a good option for many outdoor work environments when no additional radiant heat sources are available.

The Heat Safety Tool app, in addition to calculating the heat index, provides recommendations to prevent heat-related illnesses and reduce heat stress in outdoor workers. Each calculated heat index is associated with a risk level, and the “Precautions” option gives recommendations specific to each risk level. Supervisors interested in planning work activities for the entire shift around the heat index can use the hourly feature to determine the hottest hours of the day. The app also contains information on risk factors, heat-related illness symptoms, first aid, preparing for emergencies, training, acclimatization, hydration, monitoring workers for heat-related illness, and scheduling breaks.

Hot jobs should never become deadly jobs, as there are many tools for monitoring and options for managing the heat. Take precautions to keep your workers cool and safe for the entire summer, dog days included.

To install the FREE app on your device in English or Spanish, visit iTunes (iOS) or Google Play (Android).

For more information about heat stress, visit NIOSH Heat Stress.