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
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
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