Effects of ventilated safety helmets in a hot environment

Forest workers are likely to remove head protection in hot and humid condit ions because of thermal discomfort. However, a recent Occupational Safety a nd Health Administration (OSHA) regulation revision requires all workers in logging operations to wear safety helmets. thus creating a compliance prob lem. To determine which factors contribute to forest workers. thermal disco mfort, this study evaluated subjects' physiological and psychophysical resp onses during tasks approximating the workload of forest workers in a high-t emperature environment similar to that found in the southeastern United Sta tes during the summer. Environmental conditions in the helmet dome space we re also evaluated. Three helmets were used in this study: a standard helmet , a passively ventilated helmet, and an actively ventilated helmet. It was found that none of the tested helmets burdened the body significantly for t he physiological variables that were examined. Evaluation of the dome space environmental conditions showed that both the dry-bulb temperature (DBT) a nd wet-bulb temperature (WBT) varied significantly among the helmets tested . Psychophysical results showed that ventilation contributes to greater hel met comfort, and that weight and fit are important factors in helmet design .