Transdermally emitted gasses are detected byapplying a dermal sampling strip to the skin of a biologicalsubject, capturing the gasses in a vapor space in the dermalsampling strip, and analyzing for at least one such gas capturedin the vapor space of the dermal sampling strip. Analysisis preferably performed using an electrocatalytic cell,which can be mounted on the dermal sampling strip and forma wall of the vapor space.