Apparatus for detecting and monitoring exhaled breath

A breath sensor apparatus configured to measure levels of nitric oxide and isoprene in exhaled breath from a subject comprising:

• a receiver configured to receive an exhaled breath from the subject;
• a breath processing unit connected to the receiver and configured to receive the exhaled breath, wherein the breath processing unit is operated within a temperature range of 25° C. to 400° C., wherein the breath processing unit comprises:
• a γ-WO3 surface which is configured to respond to nitric oxide to alter an electrical property of the γ-WO3 surface, wherein the γ-WO3 surface is undoped;
• and
• a h-WO3 surface which is configured to respond to isoprene to alter an electrical property of the h-WO3 surface, wherein the h-WO3 surface is undoped;
• and
• a data processing unit configured to correlate the electrical property of the γ-WO3 surface with a concentration of nitric oxide in the exhaled breath, and the electrical property of the h-WO3 surface with a concentration of isoprene in the exhaled breath.