Effects of workplace thermal conditions on safe work behavior

The effect of workplace thermal conditions on worker safety has not previously been adequately investigated, due in part to the difficulty of defining a suitable safety performance measure. This report describes a study conducted in two industrial plants to determine if a correlation exists between the safety-related behavior of workers and workplace thermal conditions. Both heat exposure measurements and behavioral observations were taken over a 14-month period, for a total of over 17,000 observations. The results indicate that temperatures below and above those typically preferred by most people have a significantly detrimental effect on the safety-related behavior of workers. This is demonstrated by an index based on the ratio of observed unsafe behaviors to the total number of observed behaviors. The relationship between this index of unsafe behavior and the ambient temperature formed a U-shaped curve. The minimum unsafe behavior index occurred within the zone of preferred temperature (approximately 17°C to 23°C, WBGT). Other factors such as metabolic workload and time during the shift also had significant effects on worker safety-related behavior.