Patent ID: 7942825

Claim:
A method for continuous non-invasive monitoring of thermal stress of a user, the method comprising the steps of: a) providing a device comprising, at least one first temperature sensor configured to be placed in thermal contact with skin of the user, at least one second temperature sensor, and an insulating layer positioned between the first and second temperature sensor, where the insulating layer comprises an outer periphery and a thermal conductance (L band ), where the thermal conductance (L band ) of the insulating layer satisfies the following equation 1 + 2 ⁢ L band 2 L core 2 + 2 ⁢ L band L core ≤ 10 where L core is between 36 and 140 W/m 2 K, and where the temperature sensors are located at least a distance (w) from a peripheral edge of the insulating layer, where the distance (w) satisfies the following equation w = 0.0436 ⁢ D core ⁢ 72090 + 1101 ⁢ Q evap + 118 ⁢ Q evap ⁢ L band L band where Q evap is 250 W/m 2 or less, and where D core is between 0.002 and 0.005 meters b) placing said device in thermal contact with the skin of the user; c) determining heat flux from the skin through the device at known time intervals; and d) determining core temperature and change in core temperature as a function of heat flux.