Prevent Heat Illnesses
From 1999 to 2013 deaths from heat averaged 1.5/million population annually as reported by the EPA.
Heat illnesses – heat exhaustion, heat cramps and heat stroke can lead to death. These illnesses and deaths are preventable. Heat illness results when the core body temperature exceeds 104F and is evidenced by heat cramps, heat exhaustion and heat stroke. Heat stroke frequently results in death. Measuremment of core body temperature is intrusive and uncomfortable for workers and not easily done on a routine basis. There is no OSHA standard for work in hot environments which can lead to heat illnesses. Citations for heat illnesses are under the “General Duty Clause”
Work to develop a tool for monitoring conditions leading to heat illnesses was spearheaded by the Navy. The instrument they developed is known as a WBGT heat stress monitor. This measures wet bulb and dry bulb temperature, ambient temperature and radiant (globe or black body) temperature, hence the acronym WBGT. These values are used to compute an indoor or outdoor WBGT temperature index, from which recommended work/rest cycles are derived by referring to empirically derived charts/tables listing work/rest period frequency and duration.
The latest instruments do not rely on a wetted thermometer for measuring the wet bulb readings to calculate humidity as did the early instruments. They also use a much smaller black body, globe, sensing element for radiant temperature. Without the wetted bulb, the need for a water tank has been done away with and lengthy measurement periods are routinely done. The elimination of the wet bulb also removed the need for replenishing a water reservoir and the periodic cleaning of the system.
These newer instruments have other advantages including being easily handheld, light weight, many offer on-board datalogging and direct calculation of indoor and outdoor WBGT temperature indexes. The WBGT indexes are used to establish work/rest cycles for heat-acclimated persons under varying work level conditions such as light, medium and high exertion levels. Examples of the latest handheld WBGT heat stress monitors, and a wall mounted WBGT instrument are shown below. Click on any of the instruments for additional information on that instrument.