CO2 Sensors

What are CO2 sensors?

A carbon dioxide (CO2) sensor is a device used to measure the concentration of carbon dioxide gas in the surrounding area. CO2 can be found and measured both outdoors and indoors and is measured using “parts per million” (ppm) and typically has a concentration of around 400 ppm outside.

Carbon dioxide is an odorless and colorless gas created during respiration, combustion and organic decomposition. CO2 concentrations indoors are a combination of both external atmospheric CO2 and internal production from the presence of people.

Why should I install a CO2 sensor?

CO2 sensors can act like a canary in a coal mine and alert occupants when CO­2 reach pre-programmed levels. High levels of CO2 (generally above 1100 ppm) can be used to indicate when ventilation rates are not sufficient due to design, mechanical, improper maintenance or other problems. CO2 by itself is arguably dangerous, but many studies have also shown that occupants in buildings with high levels of CO2 perform up to 15% less effectively[1] and have much higher levels of sickness and absences than occupants of buildings with lower CO2 levels.

Once a Ventilation Verification assessment has been performed, to verify the condition of your current HVAC infrastructure, a design professional can help you determine if other sensors, including particulate meters and direct outside air monitors, should be added to your HVAC system. CO2 monitors are commonly recommended as a starting point due to their relatively low cost and accessibility.

How do I select a CO2 sensor?

There are different styles and manufacturers of CO2 sensors and different factors to consider when selecting the best CO2 sensors for your building – including the price and how the sensors will be powered. For an overview of different CO2 sensors as well as product evaluations, visit the Empower Procurement website.

How do I find someone to install CO2 sensors?

The best way to ensure your CO2 sensors operate correctly is to have a skilled, trained and certified workforce perform the assessment, calibrate and/or install them. Improper installation can produce unreliable readings and false alarms. You can locate contractors that employ these workers in your community here.


Fisk, W. J., The ventilation problem in schools: literature review, Indoor Air. 2017;27:1039–1051 (