Controlling Heat Exposure FAQs | Facilities Management

The heat index is a numerical value based on an area’s actual temperature and % relative humidity. The higher the temperature and relative humidity the warmer it feels. So, the heat index provides a measure of what the temperature actually feels like.

We rely primarily on the National Weather Service for the heat index forecast.

We consult the NIOSH-OSHA Heat Tool for the severity of the heat index.

The NIOSH-OSHA Heat Tool categorizes warm-hot outside temperatures into 3 risk categories—caution, warning, and danger.

Caution: 70-79°F

Warning: 80°-93°F

Danger: >93°F

There are circumstances when we should generate a local heat index to effectively evaluate heat exposures. This applies to work both inside and outside under certain circumstances.

The heat index, as provided by the NIOSH Heat App or by the National Weather Service, is based on the outside temperature and humidity. These indices also presume light shading and a light breeze.

We may have work sites or conditions where the heat index does not sufficiently model the local heat conditions. FM Safety has monitors that measure local temperature, humidity, wind speed, and the angle of the sun. These monitors generate a 'wet bulb globe thermometer' temperature, which is the site-specific heat index. These monitors can also be used inside.

FM S&EM heat issues cautionary advisory notices or excessive heat advisory notices based on several factors:

Once the hat index exceeds 80°F, FM S&EM reviews the potential for heat overexposure during FM’s working hours.

Cautionary Advisory Notices

Spring, heat index >85°F
Early summer, heat index 85-93°F.

Excessive Heat Advisory Notices

Early summer, heat index >93°F

Late summer, heat index >98°F

FM S&EM, in consultation with FM senior leadership, may issue a work stand down direction for all non-emergency outside work and inside work in locations without air conditioning. These notices direct supervisors to limit work after a specified hour based on the heat index forecast. These FM wide excessive heat stand downs are most likely when the heat index exceeds 98°F.

Come to work well hydrated. If you start the day poorly hydrated, your body will struggle to gain a state of good hydration.
Come to work well rested. Working in hot conditions is more tiring than working in cooler conditions. If you start the day tired, your body may struggle to deal with the impact of additional heat load. You may be more apt to experience heat stress.
Do not wait until you feel thirsty to drink water or non-caffeinated fluids. You are more likely to maintain good hydration by drinking smaller volumes more frequently than to drink a large volume after thirst sets in.
Pace your work or work a little slower than normal—the more exertion the body experiences in hot conditions, the greater the heat load on the body.
Rest periodically in a shaded or air conditioned location. Do not wait until you feel tired or unwell before taking a short break. Once the body overheats it takes longer to cool down and recover.

Maintaining good hydration and resting periodically when working in hot conditions are important measures that we all must take to control the risk of heat stress.

FM has many additional protective controls in its heat safety toolbox to further control heat exposure. These controls include modifying work schedules, front-loading heavy work to cooler periods of the year or day, spot cooling, portable ventilation (fans), initiating work/rest schedules, using tents to shade sunny work locations, and heat safety standdowns.

Heat illness prevention measures are most effective when good hydration and rest breaks are combined with appropriate administrative and engineering controls.

Acclimatization is increased heat tolerance from gradual exposure to increasing environmental temperatures.

There are 6 commonly recognized illnesses or conditions associated with heat overexposure.

Heat rash
Heat cramps
Heat syncope
Rhabdomyolysis
Heat Exhaustion
Heat Stroke