The Impact of Installation on the Measurement of Black Globe Temperature

Extreme heat is the deadliest meteorological phenomenon in human history. Today, a large number of people around the world are based in hot, humid, and poorly-ventilated workplaces, where they are at risk of developing heat-related illnesses. Wet-bulb globe temperature (WBGT) combines factors such as air temperature, solar radiation, humidity, and wind speed into one measurement that assesses heat stress risk. The Campbell Scientific BLACKGLOBE-L measures the black globe temperature, or radiant temperature, which is one component of WBGT. The black globe measurement is responsive to shadowing and can be heavily influenced by the installation of the globe. A recent study suggested that a black globe sensor with an off-vertical cable gland and a temperature probe that is not centered within the globe can underestimate WBGT by up to one category of heat stress risk. To test this, we performed a series of manipulations upon an ensemble of black globes, altering the orientation angle and temperature probe insertion depth. We have observed that installing a black globe with its cable gland vertically oriented and its temperature probe centered within the globe can increase the measured black globe temperature by a maximum of 4°C . While this is a significantly altered reading, there exists no reference measurement to which we can compare our findings, only the ISO 7243 standard. To better understand these results, further investigation is needed, including the potential effects of thermal conduction across the length of the temperature probe. This will provide a clearer direction in improving our assessment of black globe temperature and daily heat stress risk.