The ASHRAE Standard 55-1981 specifies temperature limits or zones for winter and summer comfort. It states that the upper limit of the summer comfort zone, which is 79/sup 0/F or 26/sup 0/C, can be extended to 82/sup 0/F or 28/sup 0/C with air velocities of 160 fpm or 0.8 m/s. The manufacturers of ceiling fans claim comfort may be obtained at velocities considerably below the 160 fpm (0.8 m/s) level. They further claim that 82/sup 0/F (28/sup 0/C) with a ceiling fan will provide the same amount of comfort as 75/sup 0/F (24/sup 0/C) without a fan. Since ceiling fans require less than a penny per hour to operate, their use, as opposed to air conditioning, could represent a large energy savings without affecting human comfort. The National Bureau of Standards suggests a reduction in air conditioning demand of 3%//sup 0/F (5.4%/C). Thus the energy saving provided by 140 fpm (0.7 m/s) from a ceiling fan would be 5.6/sup 0/F X 3%//sup 0/F = 17%. Thus it was concluded that a ceiling fan may extend the upper limit of the summer comfort envelope from 79/sup 0/F (26/sup 0/C) to 85/sup 0/F (29/sup 0/C) (the equivalent temperature on any specific situationmore » depends on the velocity of the air on the person). The results suggest that the turbulent and variable characteristics of the air plume of the ceiling fan may be its major comfort-producing feature.« less