Fig. (6) Typical curves for temperature of ambient air, air flow rate, temperature, relative humidity and CO2 concentration of exhaled breath gas for a test participant after walking for 5 min.Te, the exhaled air temperature in °C, RHe, the exhaled air relative humidity in % M’ is the air flow rate in m3/s, Ta is the ambient air temperature in °C, CO2-e is the CO2 concentration of ambient air in ppm.