A is for
AIR CONDITIONING
The supernatural temperature drop during the exorcism scene required the actors’ breath to be visible. Easily done now via CG, but in 1973 a practical solution was required. “What we did was place a gigantic restaurant air conditioner across the top of the set,” director William Friedkin explained. “At the end of each day’s shooting, we turned on the A/C all night so by the next morning it was 40 below zero [4.4 C].” [1] Small clip lights were also attached to the back of furniture, so that the cast’s breath registered clearly.