AIHA — the association for scientists and professionals dedicated to occupational and environmental health and safety (OEHS) — announces the release of Heat Stress App 2.0 , its next-generation mobile tool that now includes risk factors unique to indoor workers. This new version follows the successful launch of AIHA’s original heat stress app, which helped outdoor workers and their employers assess job-related heat health risks.

“While heat stress risks for outdoor workers are more obvious due to intense sunlight and high outdoor temperatures and humidity levels, heat stress that workers face in indoor environments may be vastly underestimated—especially when there is a localized heat source, such as a hot oven or furnace,” said Lawrence D. Sloan, CEO of AIHA. “We encourage indoor workers and their employers to use our next generation heat stress app to recognize the factors that can cause heat-related illnesses and monitor the indoor environment in real time for signs of heat-related illness.”

This free app now allows users to select whether they work indoors or outdoors, which then prompts them to select specific criteria about their workplace. For example, while the original heat stress app measured outdoor factors such as the user’s exact location and degree of sun exposure, the next generation heat stress app for indoor workers measures the following heat risk factors that can pose considerable health risks for workers in an indoor space:

• Indoor temperature (exact temperature or temperature difference between outdoors and indoors)
•  Relative humidity
• Non-solar heat irradiance (radiation emitted from hot equipment or material that may significantly contribute to the amount of environmental heat)
• Wind speed
• Workload intensity (users can select light, moderate, heavy, very heavy)
• Clothing worn

Similar to the first-generation app for outdoor workers, the updated app relies on the Wet Bulb Globe Temperature (WBGT) index — considered the gold standard for evaluating environmental heat stress — using the indoor temperature function which translates the data to a corresponding heat stress risk using the app’s current algorithm. The app also delivers heat alerts as well as health recommendations (i.e., rest breaks and water consumption) based on an individual’s risk level. Additional resources available include fast reads on recommended heat stress prevention measures, warning signs of heat-related illness, and recommendations for heat acclimatization.

AIHA heat stress experts note that in indoor workspaces such as warehouses where there is a lack of climate control — notably air conditioning — or proper ventilation, heat exposure may build up due to external heat sources from high ambient temperatures and indirect solar radiant heat even though no significant indoor heat sources are present. The most common indoor sources of heat stress in the workplace include furnaces, ovens, boilers, and molten materials such as metal and glass. Heat stress from indoor heat exposures may be commonly found in foundries, commercial kitchens, and warehouses. Heat experts warn that indoor exposure to extreme heat can result in occupational illnesses caused by heat stress, including heat stroke, heat exhaustion, cardiac events, kidney injury, or even death. Heat can also increase workers’ risk of injuries, as it may result in sweaty palms, fogged-up safety glasses, dizziness, and may reduce brain function responsible for reasoning ability — creating additional hazards.

“The main differences in heat stress between indoor and outdoor workplaces are the heat sources and workplace conditions that may contribute to heat stress,” said Jo Anne Balanay, PhD, CIH, a professor of environmental and occupational health at East Carolina University and a long-time member of AIHA. “Indoor workers experiencing heat stress due to hot machineries and materials may benefit from a break away from the hot environment, whereas outdoor workers may benefit from having a break in the shade and spending time in naturally windy conditions to cool down their body. Indoor workers, on the other hand, may be disadvantaged by poor air circulation that limits heat dissipation.

Developed by leading OEHS heat safety experts from the AIHA’s Thermal Stress Working Group in partnership with East Carolina University, the next generation AIHA Heat Stress Mobile App is now available as a free download on both iOS and Android platforms and is available in four languages — English, Spanish, French or Portuguese. AIHA’s first generation heat stress mobile app for outdoor workers launched last summer, as 2024 shattered heat records as the hottest year on record around the world.

As part of AIHA’s ongoing commitment to raising awareness of the dangers of occupational heat stress, free resources devoted to workplace heat stress are available on its Healthier Workplaces webpage. A separate section for employees outlines personal risk factors that increase one’s risk of heat-related injuries or illnesses on the job, tools to assess personal fluid needs, and important warning signs and symptoms of exertional heat stroke. In addition,  employers can find strategies to establish evidence-based heat stress protocols designed to safeguard both indoor and outdoor workers.