The use of personal protective equipment (PPE) can prevent the transmission of COVID-19.  However, it also has the potential to cause excessive physiological responses. This study aims to investigate the effect of the physical work environment (temperature) on physiological responses related to activities using level III PPE for handling COVID-19 with laboratory experiments. Twelve participants (age 23.7 ± 2.4 years, BMI 24.3 ± 3.3 kg/m²) wore level III PPE and carried out simulated activities in three different working temperatures (20 ?C, 25 ?C and 30 ?C with relative humidity 50 ± 10 %). The experimental activities consisted of walking on a treadmill (speed of 2.9 km/hour), filling out logic-base puzzles, walking on a treadmill, filling out logic-base puzzles, walking on a treadmill, and bedding. Each activity was carried out for 9 minutes and the transfer time was 1 minute. At the end of each activity, physiological responses were measured including heart rate, oxygen consumption, and blood pressure. The results of this study show that working temperature had a significant effect on heart rate (p=0.002) and systolic blood pressure (p=0.043) but had no significant effect on oxygen consumption (p=0.411). A post-hoc analysis demonstrates that the working temperature of 30 ?C had effects that were different from the other two conditions.  It is concluded that wearing a PPE at a relatively high working temperature can result in undue physiological strains.  Findings of this study can be used as a basis for work and PPE redesigns.