Detecting CO2 is essential to prevent the risks associated with this dangerous gas. It is present in various environments and can be emitted by different sources. Excessive levels of CO2 in the air can be critical to health. That’s why we strongly recommend the installation of CO2 detectors, especially in public buildings and workplaces.

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Published on 15 January 2024

How do you detect CO2?

In this article:

CO2: a dangerous gas

Carbon dioxide (CO2) is present in all types of environment. We can find it both indoors and outdoors. It can present risks for the most vulnerable, such as children and the elderly. Emissions of this gas at normal levels pose no risk. However, if its concentration in the air becomes too high, it can be dangerous.

It can be emitted from various sources, such as :

  • Heating appliances
  • Tobacco smoke
  • Household appliances
  • Household equipment

Depending on your exposure, you may experience different symptoms. This gas enters the lungs and is transported to the pulmonary alveoli. It also passes through the bloodstream to the red blood cells. It is therefore important to avoid inhaling too much carbon dioxide.


The law established for ERP (Etablissements Recevant du Public) establishments

A regulatory revision came into force on January1, 2023. This law mainly concerns ERP buildings such as schools, colleges, lycées and others. These establishments have until December 31, 2024 to carry out their annual assessment of ventilation systems.

In addition, from January1, 2025, social, medico-social and long-term care facilities attached to healthcare establishments will be subject to this law. The measures are designed to improve IAQ (Indoor Air Quality) in these buildings.

Four essential points are then retained in these measures:

  1. IAQ self-diagnosis at least every four years
  2. Annual assessment of ventilation systems, including direct measurement of CO2 concentration in enclosed environments
  3. An action plan taking into account the annual assessment of ventilation systems, the self-diagnosis and the measurement campaign indicated above
  4. A series of pollutant measurements carried out at each key stage in the life of the building by an accredited body

The aim is to promote energy efficiency and reduce indoor air pollution.


How to detect carbon dioxide

CO2 levels in a closed environment are a good indicator of air quality. It is calculated in Parts Per Million (PPM) and read by a direct-reading sensor. This measuring device monitors indoor environments. When CO2 is detected in a room, the product emits a powerful light visible from over 5 meters away. The CO2 level is then transmitted to the occupant quickly and easily. This type of sensor is designed so that anyone can use it.

To avoid risks, it is strongly recommended to install gas detection equipment. In fact, there are two reasons why it is important:

  • For safety: carbon dioxide is dangerous, even deadly. Too high a concentration in a confined space can lead to health effects for the occupants. In extreme cases, exposure to this gas can cause death.
  • For Indoor Air Quality: too high a concentration degrades IAQ. It can cause dizziness, reduced concentration and an increased risk of respiratory infection. An amount of CO2 equivalent to 1% in a room causes headaches and dizziness. Above 5%, the individual may lose consciousness.


How to avoid CO2?

Carbon dioxide can be avoided. Here is a list of good practices to follow:

  • Installing a CO2 detector
  • Ventilate spaces by opening windows and doors
  • Limit consumption of fuels such as wood, coal, oil or natural gas
  • Apply safety instructions when working indoors
  • Insulating homes
  • Buying houseplants

The direct-reading carbon dioxide sensor remains the best way to detect this gas. These products are designed to easily detect CO2 for you.


What are the solutions?

The direct-reading sensor

The direct-reading sensor is a device for measuring carbon dioxide in indoor environments. This product has the ability to warn occupants of a confined space of changes in Indoor Air Quality visually. The product generally features a display or LED to make it easier to understand the message sent by the sensor. No technical skills are required to use it.

CO2 sensors from Nexelec

Nexelec offers a wide range of sensors designed for Indoor Air Quality. The products constantly analyze the IAQ of your indoor environments. The carbon dioxide level is indicated by a tricolor LED. For ease of understanding, the lights change color when the sensor has detected CO2. The different lights correspond to different thresholds:

  • Red (1500 ppm): IAQ is poor, the room must be ventilated immediately to renew the air.
  • Orange (< 800 ppm): Indoor Air Quality is poor. Renew the air as soon as possible
  • Green (> 800 ppm): a healthy environment

Thanks to the advanced technologies used in the products, many parameters can be configured via NFC from a smartphone. For example, the LED can be customized as required: you can change the CO2 detection thresholds.

These LoRaWAN-connected products can also measurehumidity levels and room temperature. The range also includes detectors capable of analyzing other parameters such as :

Nexelec detectors have been extensively tested to ensure compliance with current standards. The Conformité Européenne (CE) and UK Conformity Assessed (UKCA) certifications comply with the regulations drawn up in January 2023 by the French government, and in January 2021 by the British government.


Where to install the product?

Installation of a carbon dioxide sensor depends on the context and the monitoring objective. The product can be installed in a variety of locations, such as :

Housing :

  • Near potential sources of CO2 emissions, such as chimneys, gas heating systems, stoves and garages
  • In bedrooms, when auxiliary heaters are used

Workspaces :

  • In offices, meeting rooms and open spaces to monitor IAQ
  • In laboratories, where chemical reactions can generate this type of gas
  • In plants and production facilities to ensure worker safety

Establishments open to the public (ERP) :

  • In classrooms, gymnasiums or auditoriums
  • In restaurants and bars

There are many places where it’s important to install a carbon dioxide detector. The device will help you establish your indoor air renewal strategies.


In short, carbon dioxide is a pollutant that travels a long way in the air we breathe. Investing in a CO2 sensor remains one of the best ways to prevent hazards. These devices can be used in a wide range of environments, from homes to workplaces, to guarantee safety and comfort for all. What’s more, the adoption of good practices such as regular ventilation and emission reduction plays a crucial role in preventing CO2-related hazards.