Can You Recommend a CO2 sensor for the Raspberry Pi3?

I'll start out by saying I work for a company that sells some of the CO2 sensors below. I know this post is 6 months old, but I thought I could add some information not mentioned here.

CO2 sensors can be broadly broken into 2 camps: non-dispersive infrared (NDIR) and electrochemical (EC). If you breath on them, both will measure a change in CO2, but there are differences.

NDIR sensors include SenseAir, GSS, Teleaire by Amphenol, Winsen, Figaro (new), and others. They tend to be faster, last longer, and are more accurate. Price $85 and up.  They will last a decade or more. NDIR uses light to measure the wavelength of the CO2 molecule. These are used in almost every commercial-grade CO2 transmitter for HVAC, to measure plant and animal respiration, or any application that depends on fast response (some like the GSS SprintIR make up to 20 readings per second!). Included in this list is the GSS COZIR, which uses an LED lamp instead of infrared to save power. Very cool tech, but it costs a few dollars more.

EC sensors like the older Figaro line or the mg-811 tend to be smaller, cheaper, slower, and have a shorter shelf life. Price $10 and up. They measure changes in a chemical reaction inside the sensor. The chemicals inside have a shelf life, anywhere from 1-3 years. Also, because these rely on chemistry, they tend to take a few minutes to see a change in CO2 levels. However, because of their low price, they tend to be popular in consumer products and for use by hobbyists.

If I was going to hook a CO2 sensor up just to show changes in indoor CO2 (for example, good vs. bad IAQ) any EC sensor will work. If I needed more accurate measurements (like changes from 400ppm to 500ppm) and ease of integration I'd look at a COZIR. If I needed complete control, analog or I2C output, high accuracy and proven technology, the SenseAir K30 would be a top contender.

I'll start out by saying I work for a company that sells some of the CO2 sensors below. I know this post is 6 months old, but I thought I could add some information not mentioned here.

CO2 sensors can be broadly broken into 2 camps: non-dispersive infrared (NDIR) and electrochemical (EC). If you breath on them, both will measure a change in CO2, but there are differences.

NDIR sensors include SenseAir, GSS, Teleaire by Amphenol, Winsen, Figaro (new), and others. They tend to be faster, last longer, and are more accurate. Price $85 and up.  They will last a decade or more. NDIR uses light to measure the wavelength of the CO2 molecule. These are used in almost every commercial-grade CO2 transmitter for HVAC, to measure plant and animal respiration, or any application that depends on fast response (some like the GSS SprintIR make up to 20 readings per second!). Included in this list is the GSS COZIR, which uses an LED lamp instead of infrared to save power. Very cool tech, but it costs a few dollars more.

EC sensors like the older Figaro line or the mg-811 tend to be smaller, cheaper, slower, and have a shorter shelf life. Price $10 and up. They measure changes in a chemical reaction inside the sensor. The chemicals inside have a shelf life, anywhere from 1-3 years. Also, because these rely on chemistry, they tend to take a few minutes to see a change in CO2 levels. However, because of their low price, they tend to be popular in consumer products and for use by hobbyists.

If I was going to hook a CO2 sensor up just to show changes in indoor CO2 (for example, good vs. bad IAQ) any EC sensor will work. If I needed more accurate measurements (like changes from 400ppm to 500ppm) and ease of integration I'd look at a COZIR. If I needed complete control, analog or I2C output, high accuracy and proven technology, the SenseAir K30 would be a top contender.