- Breathing machine: Respironics CA-3200
- CO2 sensors: GSS SprintIR-WF-20
- CO2 flow meter ABB PurgeMaster FP-1/4-41-G-3/37
- Pressure sensor: Sensirion SDP816-500PA
- Data aquisition: Arduino Mega
- CO2 measurement
- Cycles and volume flow
Carbon dioxide concentration
- Volume flow over sensors: Pressure differential over CO2 sensing loops are measured as well as the flow through the sensing loop.
- Adding dead volume: Dead volume is added to the system in the form of 32mm PVC piping.
Pressure drop over mask
- Volume flow: Outlet is blocked by mask
Validation test data
Volume flow over sensors
|Sensor||Pressure drop inhale||Pressure drop exhale||Flow inhale||Flow exhale|
|Exhale sensor||~0 Pa||1000 Pa||~0 L/min||5.8 L/min|
|Inhale sensor||2750 Pa||~0 Pa||11.5 L/min||~0 L/min|
Known dead volumes
|Dead volume||CO2 Exhale||CO2 Inhale||Theoretical|
Volume flow under pressure drop over mask
|Masker nr||Name||Inhale CO2 concentration [%]||Exhale CO2 concentration [%]||Inhale volume [L]|
|25||BIZTEX NIOSH N95||0.66||5.22||2.10|
|20||Dräger Piccola VRAD-F028||0.93||5.39||2.09|
|26||3M Aura 1883+||0.90||5.32||2.05|
- Pressure drop and flow over sensors show that the corresponding sensors are only experiencing a volume flow under inhalation and exhalation
- The large pressure drop over the sensors ensures a large volume flow and a short response time.
- Dead volume test shows direct correlation between the added dead volume and the measured CO2 concentration in the inhaled air
- The CO2 concentration in the inhaled air corresponds with the theorized increase by adding dead volume
- Inhale volume and exhale CO2 concentration is within +- 5% of the desired value of 2L and 5%.
- Inhale CO2 concentration without mask is higher than the ambient CO2 concentration (0.04%), this can be explained by rebreathing of the exhaled air around the dummy head. (This was also verified by elongation of the inhalation CO2 measuring tube beyond the head)
- The inhale CO2 concentration is for all masks below 1% as is expected from masks certified according to NEN 149 norm.