Finally i did a more extensive research for my main interactive project at LCC, monitoring breathing of many people resp. hearing a building breathe.
These are methods of measuring (human) respiration in the most general sense:
With touch
1. Mouth airflow
by Spirometer2. Nasal temperature probe
by thermistor3. Acoustic
by stethoscope4. Thoracic (chest) or abdominal (belly) expansion
by strap extension (e.g. using ultrasonic distance measurement)
Touchless
1. Acoustic
by ceiling dome microphone2. Thermal
by infrared imaging3. Capnographic
by measuring exhaled carbon dioxide
More Links and details are coming soon.