An experimental study was conducted in order to clarify the degree of human emotional instability under smoke conditions. Mental arith metic and walking speed were adopted as indices of emotional instability. Fur thermore, the annoyance of smoke and heat was investigated by a question naire. Emotional instability caused by a physiological factor was found to be important as well as psychological unrest under high smoke irritation. Such smoke affects thinking power and walking speed. Especially, heat with smoke was found to begin to affect thinking power in the range between 1370 kcal/m2 hr and 2030 kcal/m 2 hr. The degree of smoke annoyance decreased with the lapse of time.
