A portable system for CO2 and pressure monitoring inside the dead space of face masks

This paper presents a portable system designed to monitor physical and chemical quantities inside the dead space of face masks that are commonly used to prevent the diffusion of SARS-CoV-2 infection. The system is a “side stream” analyzer that continuously samples the gas inside the gap between the mask and the user mouth and provides, in real time, the temporal evolution of CO2 concentration, differential pressure and temperature. These quantities are related to the mask behaviour in term of breath resistance, CO2 accumulation and overheating that, in turn, can cause physiological side effects and a feeling of discomfort. These effects become more relevant when the masks are employed during physical activities, such as team sports, and for this reason the system has been designed to have a reduced weight and dimensions as well as a reduced invasiveness of the sampling line. The paper also proposes a measurement procedure for the evaluation of the CO2 inspired volume in real conditions during the physical activity. At the current stage, the proposed procedure is only able to provide qualitative measurements, but it can work in real conditions and it does not require bulky and expensive facilities as the ones required by the actual international standards for the certification of respiratory protective devices.