Why is carbon dioxide measured?

Potential safety hazard
Carbon dioxide can be a safety hazard. When the concentration of carbon dioxide rises, people start to feel tired and listless, and they have trouble concentrating. With further increases, CO₂ begins to act as an asphyxiant. Prolonged exposure to very high concentrations of carbon dioxide results in unconsciousness and even death.

As high concentrations of CO₂ are clearly hazardous, most countries have set exposure limits in the workplace. In Great Britain, for instance, the weighted average exposure limit for an 8 hour working day is 5000 ppm; a higher limit of 15,000 ppm applies to an exposure up to 10 minutes.

Applications where carbon dioxide can rise to dangerous levels include the brewing and carbonated drinks industries, food freezing using dry ice, cold storage, cargo ships, and, of course, plants where CO₂ or dry ice is produced or handled.

Air quality and ventilation
Even when the carbon dioxide concentration is not high enough to cause problems, it is a good indicator of indoor air quality in general. A high CO₂ level is usually a sign of poor ventilation and the presence of odours and other pollutants such as volatile organic compounds (VOCs). Poor ventilation also increases the risk of high humidity and in the worst case, a radon build-up in the building.
Demand Controlled Ventilation (DCV) is often based on carbon dioxide measurement. Higher concentrations of CO₂ indicate the presence of people in the room. Using DCV, conference rooms and classrooms, for example, can be ventilated only when there is an actual need for it. This ensures good quality breathing air at all times and keeps energy costs down. At the same time it helps participants in conferences and meetings stay alert and attentive.

Beneficial effects in greenhouses
On the positive side, carbon dioxide can enhance plant growth. In greenhouses and mushroom farms, the growth rate and development of mushrooms and plants - from cucumbers to most luxurious roses - can be improved by controlling the concentration of carbon dioxide. This raises the productivity and quality of the crops. In some cases, the CO₂ concentration is used to control when fruits and vegetables ripen. The concentration of CO₂, however, must be carefully adjusted. If the carbon dioxide level rises too high, the plants can be damaged or their growth stunted.

Food packaging
Adding carbon dioxide to food packaging can considerably extend the storage and shelf life of meat, cheese as well as fruit and vegetables. In meat packaging, for example, a high concentration of CO₂ in the packaging inhibits bacterial growth and retains the natural coloring of the meat.