Table 4.

Studies on thermal pain threshold not involving RF exposure (data summarized in Fig. 5).

Hardy (1953)	6 subjects, IR to forehead. Step power input (exposure levels ranged from ≈1–30 kW m−2, pulsewidth from 0.25–300 s)	“Pain was elicited when the skin temperature reached 45.7oC with a standard deviation of +/-1.7oC regardless of the time of exposure and intensity of stimulus.”
Stoll and Greene (1959)	3 subjects exposed on forearm to IR pulses and from touching hot surfaces.	Thresholds for pain and burn show similar time dependance. Later work by Stoll was the basis of current touch temperature standards for electronic equipment.
Nielsen and Arendt-Nielsen (1998)	Heat applied via thermode with different contact areas	“The heat pain threshold is influenced by the peak stimulus duration, and not by the rate of temperature change.”
Helme et al. (2004)	Heat applied by thermode, thresholds measured for “young” (30 y mean age) and “older” (78.9 y mean age) subjects, exposure duration 1–100 s. Body location where heat was applied was not specified.	“Older people have an increased threshold for thermal and electrically induced pain if the stimulus duration is kept short.”
Defrin et al. (2006)	20 subjects, skin heating from 9 cm2 heated surface at 2 oC s−1, thresholds assessed using two methods (one sensitive to response time, other not)	Threshold ranged from 44.5oC (foot) to 42.9 oC (chest) using a protocol sensitive to subject’s response time, constant 42.0 oC using a protocol not sensitive to response time.