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Carbon Dioxide Detectors Definition and Principle

carbon dioxide detectors

Carbon dioxide is a colorless, odorless gas that is widely present in the atmosphere. In the natural world, the levels of carbon dioxide are always in a dynamic equilibrium of continuous growth and consumption. Indoors, carbon dioxide tends to accumulate more easily compared to outdoor environments. Indoor carbon dioxide gas primarily originates from daily human activities. For example, each person releases approximately 1 kg of carbon dioxide per day through respiration, the average use of a computer indirectly emits 10.5 kg of carbon dioxide over a year, and processes like heating and packaging frozen food also contribute to carbon dioxide emissions. Carbon dioxide detectors can display the indoor CO2 levels and remind users to ventilate the space promptly.

Carbon dioxide detectors monitor carbon dioxide levels to improve air quality. They are also used in homes, offices and classrooms to measure indoor air quality. Common applications for CO2 detectors include monitoring IAQ, process control, indoor greenhouses, bars, restaurants, breweries and landfills.

How does a carbon dioxide detector work?

Carbon dioxide detectors operate based on the absorption of infrared light to detect the presence of CO2 molecules in the air. Carbon dioxide gas molecules can absorb a specific wavelength of infrared light while allowing other wavelengths to pass through. When infrared light passes through an air sample chamber, the amount of absorbed infrared light is directly proportional to the concentration of carbon dioxide. Therefore, the more carbon dioxide gas present, the more infrared light is absorbed. Carbon dioxide detectors calculate the concentration of CO2 by measuring the amount of infrared light that reaches the filter on the detector.

carbon dioxide detector working principle

Where does carbon dioxide come from?

Carbon dioxide gas mainly comes from natural resources (including volcanoes, animal respiration and plant decay) and human sources (mainly the burning of fossil fuels such as coal, oil, and natural gas).

carbon dioxide come from

Why do we need carbon dioxide detectors?

Improve indoor air quality

The concentration of carbon dioxide is an indicator of indoor air quality. High levels of carbon dioxide indicate poor air circulation, which can make occupants feel oxygen-deprived, leading to symptoms like headaches or drowsiness. Poor indoor air quality can also lead to increased levels of mold, bacteria, particulate matter, and viruses in the air. To ensure a comfortable living environment, you need carbon dioxide detectors to monitor indoor CO2 levels and open windows for ventilation when necessary.

Improve production safety

For businesses involved in the storage, production, or use of carbon dioxide, a CO2 leak or excessive concentration can have adverse effects on workers, leading to headaches, suffocation, or even fatalities. Therefore, it is essential to install carbon dioxide detectors in places where carbon dioxide is stored or used. The use of carbon dioxide concentration detectors allows for the timely monitoring of CO2 levels and the implementation of appropriate preventive and control measures to enhance workplace safety.

Protect environment

From an environmental protection perspective, CO2 is a greenhouse gas, and elevated concentrations can lead to global temperature increases, exacerbating the effects of global warming. Therefore, environmental protection organizations or agencies need to equip themselves with carbon dioxide detectors to monitor CO2 levels and minimize CO2 emissions as much as possible in order to protect the environment.

Where should I place a carbon dioxide detector?

This depends on your specific application:

  1. Meeting rooms or classrooms: Carbon dioxide detectors should be placed at a height of approximately 12 inches (30 centimeters) from the floor, and they should be positioned to avoid any obstructions or blockages.
  2. Home: Placement is not as critical, but typically, you can position the detector at a height of 36 to 60 inches (90-150 centimeters) from the floor.
  3. Hospitals, medical centers, laboratories, factories, and similar facilities: The devices should be positioned away from hazardous materials and equipment to ensure accurate monitoring data.

Are there different types of carbon dioxide detectors?

There are various types of carbon dioxide detectors on the market depending on the place of use and working principle. You can choose the appropriate carbon dioxide detector according to your needs.

What is the difference between CO2 and CO detectors?

Carbon monoxide (CO) gas and carbon dioxide (CO2) gas are indeed two entirely different gases. Carbon monoxide is toxic, has an irritating odor, and is flammable. Carbon dioxide is colorless, odorless, non-toxic, does not support combustion, and is even used in fire extinguishers. While carbon dioxide can naturally exist in the Earth’s atmosphere, carbon monoxide does not.

Carbon dioxide detectors do not detect CO, and CO detectors do not detect CO2. Carbon dioxide detectors typically use infrared sensors to detect gas levels in the atmosphere, while carbon monoxide detectors primarily use electrochemical sensors, gel sensors, and metal oxide semiconductor sensors.

The densities of the two gases are also different. Carbon dioxide from a gas cylinder leak is denser than air, so carbon dioxide detectors should be placed near the floor. Carbon monoxide has a density similar to that of air, so CO detectors should be placed at a higher level.

How long does a CO2 detector work?

The lifespan of gas detectors can vary depending on the type of sensors they use and the operating environment.

For carbon dioxide detectors, the lifespan is primarily dependent on the core component, which is the sensor. Electrochemical sensors, commonly used in CO2 detectors, typically have a lifespan of around 2-3 years. This is because the electrolyte within the sensor naturally depletes over time during sensor use, and even if not in use, it will still degrade. Therefore, there is usually a fixed replacement cycle, and the sensor must be replaced once it reaches the end of its lifespan.

The most common carbon dioxide detectors typically utilize non-dispersive infrared (NDIR) sensors as their core technology. When used correctly, NDIR sensors can last for 5-10 years or more.

What are the recommended carbon dioxide levels in indoor air?

According to ANSES (the French Agency for Food, Environmental and Occupational Health & Safety), the typical indoor air carbon dioxide (CO2) levels in buildings usually range from 350 to 2500 parts per million (ppm).

ANSES recommends adequate ventilation in schools and other public places to prevent CO2 levels from exceeding 1000 ppm. This is the maximum acceptable concentration of carbon dioxide in the air. In fact, exposure to even just 1000 ppm can have adverse effects and may lead to more severe health consequences, especially if the recommended CO2 concentration limits are not adhered to.

carbon balance

How to choose best carbon dioxide detectors?


The measurement range of a carbon dioxide (CO2) detector is an important consideration when selecting one, but there is no need to pursue an excessively wide range. In the natural environment, the normal concentration of CO2 gas in the air is 0.04%, which is equivalent to 400 ppm (parts per million), and in densely populated urban areas, it might reach 500 ppm. In general, indoor CO2 concentrations above 5000 ppm can severely impact human health. Therefore, for indoor use, selecting a CO2 detector with a range of 0-5000 ppm should be sufficient.


Accuracy refers to the range of error between the measurement results of a detector and the true value. It is typically expressed in units of ± ppm or ±%, where higher accuracy implies smaller errors and more reliable measurement results.


In certain locations where carbon dioxide is stored or used frequently, it's important to choose carbon dioxide detectors with alarm functionality. When the CO2 concentration in the air exceeds the set upper limit, the detector should trigger audible and email alarms to alert personnel to take prompt action.


A straightforward and easy installation process is also a crucial factor in selecting carbon dioxide detectors. If you need to install multiple CO2 detectors at various locations, a simple installation can significantly reduce labor costs.


Choose a device with a clear and user-friendly display that allows for easy access to the CO2 concentration readings. This is a straightforward requirement, but there are still some carbon dioxide detectors on the market with difficult-to-read displays.