Effect of Spatial Proximity and Human Thermal Plume on the Design of a DIY Human-Centered Thermohygrometric Monitoring System

Wearable devices have been introduced for research purposes and especially for environmental monitoring, with the aim of collecting large amounts of data. In a previous study, we addressed the measurement reliability of low-cost thermohygrometers. In this study, we aim to find out how human thermal plume could affect the measurement performance of thermohygrometers. For this purpose, we used a Do-It-Yourself device that can be easily replicated. It consists of 10 iButtons with 3D-printed brackets to position them at different distances from the body. The device was attached to the user's belt in a seated position. We considered two scenarios: a summer scenario with an air temperature of 28 °C and a clothing thermal resistance of 0.5 clo and an autumn scenario with an air temperature of 21 °C and a clothing thermal resistance of 1.0 clo. The results show that the proximity of the measurement station to the body significantly affects the accuracy of the measurements and should be considered when developing new wearable devices to assess thermal comfort. Therefore, we recommend that at least two thermohygrometers be considered in the development of a new wearable device if it is to be worn on a belt, with one positioned as close to the body as possible and the other at least 8 cm away, to determine if and how the standard thermal comfort assessment differs from the user's personal perception and whether spatial proximity might also play a role.