Two Leading CO2 Sensor Technologies
When choosing a CO2 monitor you will encounter two main sensor types: NDIR (Non-Dispersive Infrared) and Photoacoustic. Both rely on the fact that CO2 absorbs infrared light at a specific wavelength (around 4.26 micrometres), but they detect that absorption differently.
How NDIR Works
An NDIR sensor shines infrared light through a sample chamber. A detector at the opposite end measures how much light arrives. More CO2 in the chamber means more absorption and less light reaching the detector.
- Accuracy: Typically +/- 30-50 ppm
- Power draw: Moderate — fine for mains-powered units, drains batteries faster
- Size: Requires a certain optical path length, so sensors are physically larger
- Cost: Found in monitors from roughly $80 to $250
How Photoacoustic Sensors Work
Instead of measuring light directly, photoacoustic sensors detect the sound waves created when CO2 molecules absorb modulated infrared light and heat the surrounding gas.
- Accuracy: Comparable to NDIR in controlled conditions
- Power draw: Lower, making it ideal for portable monitors
- Size: Very compact
- Cost: Generally $120-$350
Head-to-Head Comparison
| Feature | NDIR | Photoacoustic | |---|---|---| | Proven track record | Decades | Newer | | Battery life | Moderate | Excellent | | Long-term drift | Needs periodic calibration | More stable over time | | Noise sensitivity | None | Can be affected | | Consumer availability | Very wide | Growing |
Which Should You Choose?
Pick NDIR if you want a stationary home or office monitor with wide model selection and proven reliability.
Pick Photoacoustic if portability and long battery life matter most — for example, checking ventilation when dining out or travelling.
Use our CO2 calculator to decide how many monitors you need and which technology suits each room.