Thermal stress monitors are specialized equipment to measure indices of how heat affects the environment and / or work conditions the performance of a worker. These instruments are governed by standards such as ISO 7243, ISO 7933 and ISO 7730 for hot environments or ISO 11079 for cold environments, and through these standards allow to calculate the different indices such as WBGT, PHS, PMV-PPD to determine when a person is exposed to thermal stress given the conditions required by the work being done taking into account both the contribution of the environment and the characteristics of the employee, their clothing and metabolic behavior. Thermal stress monitors make the balloon temperature measurement.