Carbon Dioxide (CO2) accounts for approximately 0.03% of air by volume. It is a colorless gas with no smell or taste.

Carbon dioxide is a colorless and odorless gas, which is present in the air we breathe, in very low concentrations. Classified as a ‘substance hazardous to health’ by the Health and Safety Executive – in higher concentrations carbon dioxide becomes harmful to health, and has proved to be fatal in many circumstances.

One of the biggest dangers of carbon dioxide is the fact that it is a ‘silent killer’ as it simply cannot be detected by humans, even at the highest of concentrations by our senses alone. Carbon dioxide can be detected with CO2 Monitors.

Exposure to elevated levels of carbon dioxide has the following effects:

  • 250-350 ppm: Normal, outside air-breathing level.
  • 350 – 1,000 ppm: Normal, indoor air-breathing level.
  • 1,000 – 2000 ppm: Elevated levels in poor quality air, associated with drowsiness.
  • 2,000-5,000 ppm: High Levels in Poor Air: dizziness, nausea, increased heart rate
  • >5,000 ppm: UK Long Term Exposure Limit (8 Hour Reference Period)
  • >15,000 ppm: UK Short Term Exposure Limit

In most workplaces and facilities, it’s the humans within the facility who are responsible for most of the carbon dioxide in the immediate atmosphere. Although typically safe in these concentrations – in poorly ventilated offices, workers can report feeling tired and drowsy where they themselves have contributed to elevated carbon dioxide levels.

Although elevated carbon dioxide levels can be a problem in poorly ventilated office spaces, carbon dioxide is only a danger to life in workplaces and premises that either store or use carbon dioxide in their day-to-day operations. In these premises, it’s essential that carbon dioxide monitoring and detection is in place, to ensure that the owner of a premises, fulfils their duty of care to both employees, customers, and visitors.

Wherever there is carbon dioxide on the premises, there is a risk of potentially fatal carbon dioxide leak. Carbon dioxide leaks happen day in, day out – and often prove fatal. A worker typically enters an environment with high carbon dioxide concentrations, loses consciousness, falls onto the floor – where carbon dioxide concentrations are higher still. Death then occurs through asphyxiation.

It would be a misconception to believe that these accidents only happen in industrial environments, where danger is expected. These deaths and incidents take place in a wide range of environments, including restaurants, bars, and fast food kiosks.

As local regulatory agencies look to increase the safety of workers in enclosed space environments, the need for effective and reliable carbon dioxide (CO2) monitoring has never been more important

The primary technology to achieve consistent and cost-effective analytical results in CO2 monitors and detectors today is Non-Dispersive Infrared (NDIR) analysis.

Just What Is NDIR Technology, and How Does it Work in CO2 Monitors?

Carbon dioxide (CO2) Sensor Technology Explained.

NDIR  is a gas concentration measurement method that uses the unique absorption wavelength range of select gases to determine the presence of a target gas, in this case, CO2. 

The process is relatively simple. Infrared light (or an LED) is sent from one end of a test chamber towards the other end. As the amount of CO2 entering the chamber increases, the amount of Infrared light traveling through the chamber decreases. The sensor measures this decrease in intensity. The higher the intensity of CO2, the higher the CO2 content in the environment. 

The original NDIR technology was pioneered following World War II. The original components were quite large and cumbersome. Today’s solid state monitors utilizing the NDIR process are significantly lighter and more stable. Previous generations of the monitors were more sensitive to vibration and contamination. 

Today’s dual wavelength NDIR units typically have a single detector with reference and gas optical filters . One is used as a reference, to provide stability and reference, while the gas filter provides the actual measurement. 

NDIR sensors have no actual contact with gas. This makes these monitors much more reliable, as they can be tailored to specific gases without the potential for being affected by other gases.

While many gas monitors and detector systems utilize electrochemical technology, NDIR monitors do not actually interact with the target gases – electrochemical units have the potential to interact with multiple gases, reducing their effectiveness. 

The NDIR technology is so accurate, cost-effective and versatile, engineers with the Analox Group use Non-Dispersive Infrared sensing technology in ALL of the company’s extensive range of CO2 monitoring equipment.

Analox has also incorporated Gas Filter Correlation (GFC), a specialized form of GFC/GFX that has been developed to allow highly specialized and select gas properties to be incorporated into the analyzer. In short, the monitor is “programmed” with the specific properties of CO2 and can monitor exclusively for that gas. This helps filter out unwanted gases and provide an even more safe and accurate measurement. 

Analox developers include GFC technology in the company’s widely-respected VENUS product line, and in unique OEM projects where precision and customization are necessary. 

For more details on the entire Analox line of CO2 gas monitoring solutions, contact your local Analox dealer. 

At Analox, our business has been built on the back of successful detection of carbon dioxide using a wide range of sensors, monitors, and detectors, available in portable and fixed systems – all of which can be seen below.


CO2 Calculator

There is a common misconception that if using carbon dioxide (CO2) in your facility you can stay safe by using an oxygen (O2) monitor. 

The team here at Analox want to dispel this myth so we can ensure you and your team stay safe when using and storing CO2. 

CO2 is a toxic gas meaning that even at relatively low levels it can have dangerous effects on the human body. In the event of a CO2 leak, the CO2 will begin to displace the O2 in the area, however, O2 sensors typically have alarm levels set at around 19.5% and 18% so by the time the CO2 has displaced enough oxygen to trigger these alarm levels the CO2 levels will be dangerously high.

If using CO2, your safety monitor must be a CO2 monitor, this is critical so you are alerted to any leaks at levels which still give you time to take action to keep everyone safe.  This also helps to save you money as leaks can be addressed early and in the current times of CO2 shortages, protecting this precious resource is key to any business. 

We’ve made this calculator so you can check the resultant O2 levels when the ambient CO2 level changes.

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SLOT Specified level of toxicity (1 - 5% of fatalities)

SLOD Significant likelihood of death (50% fatalities)

Remember: You CANNOT use an O2 sensor to measure CO2 levels. CO2 levels become hazardous to life long before the CO2 displaces enough O2 for it to trigger an O2 alarm.

Analox provides the following carbon dioxide (CO2) gas monitoring and detection solutions:

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Protecting your crew in high-risk spaces.



A multi-gas analyzer to measure: oxygen (O2), carbon dioxide (CO2), carbon monoxide (CO), Volatile Organic Compounds (VOC's) and Dew Point in compressed air. The unit can be wall mounted or used as a portable system.

Ax60 O2 CO2 Blue Alarm


If you need a simple, ready to install and cost-effective gas safety monitor - we’ve got you covered. The Ax60+ is easy to install and already programmed for your local regulations.

AX60+ Kiosk CO2 Sensor & Alarm


A wall mountable carbon dioxide (CO2) monitor and alarm.

Analox Ax60+ Data Output Module


The DOM can be retro fitted to any existing Ax60+ installations and provides real-time monitoring of the Ax60+ and communicates with customers remote systems such as a Building Management System (BMS).

5S MKIII CO2 Transducer


A single gas NDIR (Non-Dispersive infrared) sensor for carbon dioxide (CO2).

A50 01


A single point wall mounted safety monitor for carbon dioxide (CO2) enrichment. Typically found in restaurants, pubs, bars, fast food establishments, breweries, hospitality venues, laboratories and medical centers. Due to American legislation, this is not suitable for the American market, please look at the Ax60+.

CO2 Buddy


A portable, personal safety monitor for carbon dioxide (CO2) enrichment.



A portable, personal safety monitor for both carbon dioxide (CO2) enrichment and oxygen (O2) enrichment and depletion.



A compact portable analyzer used as a backup monitor on board submarines and at altitude. The unit can simultaneously sense both oxygen (O2) and carbon dioxide (CO2), whilst providing pressure corrected readings for both.

Air Quality Guardian CO2 Monitor


Air Quality Guardian, A portable air quality monitor alerting you to the need to ventilate your area specifically to measure levels of CO2.



A panel mount, safety monitor for oxygen (O2) and carbon dioxide (CO2)

Venus Pro


A process gas analyzer for single or multi-gas monitoring.



The SDA carbon dioxide (CO2) monitor provides reliable carbon dioxide (CO2) monitoring to maintain a comfortable and safe saturation diving chamber.

SV-Multisensor 2 Oxygen (O2) & Carbon Dioxide (CO2) Monitor

SV-MULTISENSOR 2 Oxygen (O2) & Carbon Dioxide (CO2) Monitor

A compact, highly accurate electrochemical oxygen (O2) and NDIR carbon dioxide (CO2) sensor designed for vehicles operating in the upper atmosphere.

Fun Fact

Carbon gets its name from the Latin word carbo, which means "coal".

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