Page 56 - OHS, July/August 2024

SUMMER HAZARDS
Wet Bulb Globe Temperature (WBGT) in Heat Safety
The Wet Bulb Globe Temperature (WBGT) enables organizations to implement effective safety protocols and protect workers from heat-related dangers.
BY ZACK BRAUN AND DONALD D. ELSWICK
Step into an oppressive environment where the air hangs heavy like a suffocating shroud, each breath a labor, each movement a struggle against the relentless heat. This isn’t just discomfort; it’s a threat known as heat stress. A beacon of hope exists: the Wet Bulb Globe Temperature (WBGT). Let’s delve into the critical significance of WBGT and how organizations can wield it to safeguard workers against heat-induced dangers.
What is the Wet Bulb Globe Temperature (WBGT)?
The WBGT is a sophisticated metric that goes beyond mere tem- perature readings. It’s a holistic gauge that incorporates multiple environmental factors impacting the body’s response to heat stress. Unlike conventional measures like the heat index—which solely focuses on temperature and humidity—WBGT takes into account a broader spectrum of influences. It considers not only the ambient air temperature but also factors in humidity, wind speed, and the effects of both solar and thermal radiation. By amalgamating these variables, WBGT provides a comprehensive evaluation of the en- vironmental conditions that contribute to heat stress. This multi- faceted approach makes WBGT an indispensable tool for assessing workplace safety in environments where high temperatures pose a significant risk to workers’ well-being.
Why WBGT Matters
In an era of escalating global temperatures and heatwaves, heat-re- lated ailments loom large over workplaces worldwide. Heat stress isn’t just discomfort; it’s a menacing threat, capable of triggering grave health complications such as heat stroke, dehydration and tragically, even fatalities. Moreover, it takes a toll on productivity and focus, paving the way for heightened errors and accidents.
WBGT is a beacon of hope amidst the scorching haze. This vital metric empowers employers to act for heat safety protocols, thus safeguarding the well-being of their workforce without sacrificing operational efficiency. WBGT isn’t just a number; it’s a strategic tool for tailored risk mitigation. By leveraging WBGT insights, or- ganizations can recalibrate their operations to navigate heat risks effectively. This might entail strategic scheduling to capitalize on cooler periods of the day, orchestrating work-rest cycles to facili- tate adequate recovery, and establishing accessible cooling zones supplemented with ample hydration resources.
WBGT readings serve as a guide to PPE selection and usage. Armed with this data, employers can outfit their teams with gear designed to regulate core body temperature within safe bounds, further fortifying their defenses against heat-induced hazards.
Components of WBGT
WBGT equipment uses three critical environmental factors to as- sess heat stress risk, capturing the thermal environment affecting human comfort and health.
■ Natural wet bulb temperature. Measures the cooling ef- 54 Occupational Health & Safety | JULY/AUGUST 2024
fect of evaporation on the body using a thermometer covered in a water-soaked cloth. This reflects the temperature and humidity as well as the body’s potential for evaporative cooling. High humidity decreases evaporation, leading to higher perceived heat stress.
■ Globe temperature. Measured with a globe thermometer, this gauges the amount of radiant heat present, significantly affect- ing heat stress levels. The black globe absorbs radiant heat, mim- icking the heat absorption by the human body.
■ Air temperature. The ambient air temperature is measured using a standard thermometer. While straightforward, it doesn’t fully represent heat stress risk without considering humidity, wind speed or radiant heat.
Calculating the Impact
These components are measured using the following specific in- struments to ensure accuracy:
■ The natural wet bulb temperature is measured with a sling psychrometer.
■ The globe temperature requires a black sphere globe ther- mometer.
■ Air temperature is measured with a standard thermometer.
These measurements are weighted and combined according to a formula that accounts for their relative contributions to heat stress. For example, in direct sunlight, the globe temperature car- ries more weight due to the significant impact of solar radiation.
WBGT in Workplace Safety
WBGT helps organizations mitigate heat stress risks by adjusting work-rest cycles, particularly in high-temperature environments. For instance, in construction or agricultural sectors, WBGT guidelines determine the maximum duration workers should be exposed to heat. In foundries, WBGT guidelines are critical due to high ambient temperatures and radiant heat from machinery.
Developing Safety Protocols
By integrating WBGT readings into safety protocols, companies can proactively manage health risks in hot conditions, such as ad- justing the duration and intensity of work based on WBGT levels and implementing hydration breaks. Policies might dictate that when WBGT reaches a certain threshold, outdoor work is limited to 45 minutes followed by a 15-minute rest in a shaded or air-con- ditioned area. Safety protocols can include guidelines for acclima- tization, gradually increasing heat exposure to help workers adapt.
Real-World Application
WBGT is used in various industries to redesign workspaces and modify schedules. In manufacturing, companies use WBGT read- ings to incorporate ventilation systems that reduce ambient temper- ature and humidity. WBGT helps develop rotational work schedules to manage heat stress risks in oil and gas extraction operations.
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