SENSATION OF HEAT STRESS UNDER HOT ENVIRONMENTS OF WORKERS WITH DIFFERENT WORKLOADS IN OUT AND INDOOR CONDITIONS

Abstract

The present research was carried out with the objective to assess the impact of thermal environment (indoors/outdoors) on the health workers carrying different workloads (heavy, moderate, light). The outdoor study targeted subjects working in building construction area in Khartoum. The indoor study targeted subjects working in textile and glassware factories at Khartoum industrial area. The control subjects were selected from those employed at the National Health Laboratory. Thermal physical measurements included: wet-bulb globe temperature (WBGT) and heat stress indices (HSI) and physiological strain index (put on a scale from 0 to 10, PSI). Allowable exposure time (AET) was calculated from HSI and mean recovery time (MRT). A questionnaire was designed to assess sensation of stress under hot environments. HSI was shown to decrease with the decrease in workload. The results showed that, PSI increased significantly (P <.01) with the increase of workloads for both outdoor and indoor subjects. On the psychophysical scale of thermal comfort sensation (+5 to -5), all groups were uncomfortable at the afternoon but were comfortable and within the thermoneutral zone at night. Negative correlations (P <0.01) were obtained among air temperature, air velocity and HSI, but positive correlations (P <0.001) between air, radiant heat or heat strain.  It could be concluded that for workers with different loads, under hot thermal environments and with no compliance to the recommended Occupational Safety and Health Administration (OSHA, 1999) experience  heat stress with various degrees.