Influence of Phototype, Sweating and Moisturizing Lotions on Human Skin Emissivity: A Possible Cause of Screening Errors of Feverish People in Sanitary Barriers

Due to the Coronavirus Disease 2019 (Covid-19) pandemic scenario, the implementation of sanitary barriers to screening feverish individuals in places of large circulation of people was adopted, aiming to contain the disease spread. Since contamination by the virus occurs through contact and one of the most common symptoms is fever, measuring the temperature of passers-by through non-contact infrared thermography has been a technique used in sanitary barriers. One of the main factors that significantly change the temperature value indicated by thermal imagers is the emissivity of the inspected surface. Skin emissivity, a dimensionless quantity, is found in the literature with a recurrent value of 0.98. The objective of this study is to investigate whether this value is also valid for skin with sweating or using moisturizing lotions, as well as, for different phototypes. Thus, tests and evaluation of emissivity with volunteers in laboratory can answer these questions. The partial results include 37 volunteers of five skin tones of the Fitzpatrick scale, which has six phototypes. Volunteer’s thermographic images were obtained in different situations: dry skin, using moisturizing lotion, and sweaty skin. From the analysis of these images by software and using the tape method, it was possible to estimate the skin emissivity value for each situation. With the emissivity data in hand, a statistical analysis was carried out to assess whether the influence of the conditions studied is significant for the emissivity value and consequently for the temperature measured by the instruments based on the principle of infrared thermography.