Thermography based thermal comfort monitoring

Thermal stress at office work places can be caused by high room temperatures or direct solar radiation on the body and may lead to decreased productivity and health issues. An early detection of increasing body temperature allows for an adaptation of the ambient conditions through e.g. air conditioning or lowering shades.

In a joint research project with the German Research Center for Artificial Intelligence, a method was developed where changes in facial skin temperature are continuously measured and monitored using thermography. Inexpensive miniature cameras were used that could record RGB as well as IR videos. Special algorithms for object detection were used to average the evolution of skin temperature over a specific area in the face.

The participants of a pre-study were subjected to a heat source targeting their head, and every minute they had to vote their thermal sensation and thermal comfort during the experiment. A high correlation of the measured temperatures with the subjective sensation of the participants was found.

The method is now applied to a bigger study with 64 human subjects. The study aims to find a correlation of the measured temperature increase with the increase of thermal sensation on the ASHRAE 7-point-scale, and the determination of a threshold value of temperature increase over time at which an adaptation of the environmental conditions is recommenden. Furthermore, temperature increases to cognitive stress situations, as they can occur e.g. in exams, are investigated, too.