How to Measure Carbon Dioxide (CO2) for Indoor Air Quality

Carbon dioxide can sometimes get less attention than its more dangerous or even deadly sibling, carbon monoxide. But CO2 is still less than ideal for indoor air quality, especially when it reaches elevated levels due to environmental hazards or poor ventilation. That's why it's crucial to keep an eye on it. But you may be wondering - how is CO2 measured, anyway?

Why does CO2 need to be measured?

Carbon dioxide needs to be measured by technology because otherwise, you wouldn't even know it was there! CO2 is colorless and odorless, so there's no way for the human senses to detect it on their own. At moderately elevated levels, carbon dioxide can reduce performance, harm concentration, and even worsen decision-making. Over time, extreme amounts can cause headaches, dizziness, nausea, and other symptoms. CO2 can also be a sign of other, more harmful substances in the air that need to be removed from the environment as soon as possible.

Measuring CO2 in real-time allows homes, offices, schools, and other buildings to ensure healthy indoor air quality. When concentrations reach a specific level, some HVAC and other ventilation systems will kick on automatically to cycle out the old, stale air and replace it with pure, fresh air. Others will set off an alarm or notification to allow managers or supervisors to take appropriate action manually.

How is CO2 measured?

The most accurate way to measure CO2 is with sensors specifically designed to measure carbon dioxide. There are three main types - electrochemical sensors, non-dispersive infrared (NDIR) sensors, and metal oxide semiconductor (MOS) sensors. While each has its respective strengths, NDIR is the most popular choice these days due to its high reliability and speed. This means it can react quickly to changing conditions,

Carbon dioxide is measured in parts per million (ppm), which represents how many particles of CO2 are present for every million total particles of air. It's critical to measure in this way because even relatively small amounts of substances like carbon dioxide, carbon monoxide, and others can have major health impacts. Ambient levels will vary depending on the type of space and use, as well as other environmental conditions. People will feel the most comfortable across a relatively broad range on the lower end of the carbon dioxide spectrum.

How does the sensor detect CO2 levels?

We'll start with NDIR technology, which remains the top choice for most. It works by projecting infrared light into the air passing through the sensor. This light is absorbed by molecules of carbon dioxide in the atmosphere. A sensor can then determine how much light was absorbed, which is converted to a traditional CO2 reading. NDIR sensors can last for a decade or more, though extreme temperatures or humidity levels can shorten their life.

Electrochemical sensors also operate on a relatively simple principle. As air passes through the sensor, carbon monoxide molecules react with a specially-treated surface, creating an electrical charge. When the concentration of CO2 reaches a prescribed level, the electrical charge will set off the sensor. Finally, MOS sensors test carbon dioxide using a metal strip with an electrical charge flowing through it. As different substances in the air react with this strip, the level of electrical reactivity changes, producing CO2 readings.

What level of CO2 is unsafe for Indoor Air Quality?

When considering indoor air quality, it's vital to remember there's a background level of carbon dioxide in every environment, even "fresh" outdoor air. These generally have 300 to 500 ppm of CO2. Indoor spaces will necessarily have higher levels than this. Safe and comfortable levels are typically in the 700-1,200 ppm range. Negative health effects don't begin until well above this level, and it takes extremely high concentrations of 5,000 ppm or more to pose significant health risks. However, it's unlikely that most buildings will ever reach this level, even without efficient air sensors and ventilation systems.

No matter what carbon dioxide levels are currently in your building, there's always room to improve. But now that you know how CO2 is measured, you can take action. Fresher air and better ventilation can improve employee performance, mood, and productivity, among other noteworthy benefits. So check out the Veris selection of CO2 sensors to start improving your indoor air quality today.