To extract the effects of air-conditioned wear (ACW) and other factors on heat stroke, we carried out experiments to measure the physiological and psychological responses of workers simulating construction work in an artificial climate chamber at two fixed temperatures (29, 34°C), which simulate the environmental temperature at indoor and outdoor construction sites, respectively. There were two types of workers in the experiment: reinforcing bar placers (RBPs) and form workers (FWs), and they were tested with and without ACW. Physiological responses, such as the distribution of skin temperatures on the body, sublingual temperature, heart rate measured on wrist and breast, overall activity, three-directional (X, Y and Z) acceleration, body weight with and without clothing were measured; and the subjects were surveyed to assess their psychological responses. There were six RBPs and six FWs.
For the workers wearing the ACW, skin temperatures at the abdomen and back were significantly lower than those without ACW: 0.4°C and 0.4°C at 29°C, 0.5°C and 1.0°C at 34°C, respectively (P<0.001). On the other hand, the skin temperature at the forearm was significantly higher for workers wearing ACW at 29°C. These numbers indicate that the mean skin temperature is reduced mainly by cooling the abdomen and back using airflow. But the arm part of the ACW is so long and thin compared with the body part that airflow driven by fans cannot arrive at the forearm due to high resistance. Additionally, heat dissipation from the forearm is reduced by the ACW. Thus, the skin temperature at the forearm of workers wearing ACW was higher than that of workers without ACW.
Skin temperatures and sublingual temperatures of subjects wearing ACW were significantly lower than those without ACW at 34°C (P<0.001, P<0.05). ACW reduces skin temperatures and sublingual temperatures by 0.4°C and 0.1°C at 34°C, respectively. It does not have the same effect at 29°C. Furthermore, quality of sweat content of clothing with ACW was significantly less than that without ACW only at 34°C, not at 29°C. Heart rate measured on the wrist with ACW was significantly lower than that for subjects without ACW at 34°C, but not at 29°C. From these results, we can infer that the heart rate varies with the amount of sweat due to dehydration which varies significantly depending on the ambient temperature and whether the subject is wearing ACW.
On the other hand, the acceleration of RBPs in the X-direction was significantly higher than that of FWs since rebar work on low walls was done in a squatting position in this simulation. It was supposed that, in this position, the knees press against the abdomen so that the cooled air driven by the fans cannot arrive at the abdomen. Thus, the differences in skin temperatures at the abdomen between RBPs with ACW and those without were significantly lower than for FWs and for the backs of RBPs. We believe this explains why there were no significant differences in comfort and thermal sensation between RBPs with ACW and those without.
