CO 2: The criterion of efficiency of ventilation systems


The impact of indoor air quality of buildings on the health of people given special attention as environmentalists, doctors, diagnosticians, and engineers, designers of ventilation and air-conditioning. The quality of the air depends on the physical condition of the person: the poor air quality people feel unwell, loss of concentration, the development of diseases, and so on. D

By hazard, subject to the assimilation of ventilation systems, gaseous pollutants are emitted in the process of breathing and through the skin surface (ammonia, hydrogen sulfide, acetone, and so on. N.), as well as chemical volatile compounds emitted from furniture and decoration materials in the room. In the course of human breathing in normal conditions are subject to change in the concentration in the main two components of air: oxygen and carbon dioxide.

During the metabolic processes in the human body the concentration of oxygen in the exhaled air drops from 20.9 to 16.3%, and carbon dioxide, on the contrary, increases from 0.03 to 4% [4]. Attention is drawn to the fact that the concentration of carbon dioxide increases by more than 100 times.

Specialists have found that the degree of concentration of gas pollutants emitted person closely correlated with the concentration of the carbon dioxide emitted during breathing humans . In this connection, the concentration of carbon dioxide has been accepted as an indicator of air quality . Other harmful gas emissions in residential and public buildings (phenol formaldehyde, acetone, ammonia and other components allocated furniture, decoration materials) lead to carbon dioxide equivalent .

Pollutants from furniture and decoration materials (mainly formaldehyde and anilines) in relation to the hazard produced by people are largely assimilated and multidirectional airflow calculated from the concentration of CO 2. As a rule, in the absence of people in the room background ventilation rate of 0.1-0.2 h -1 is sufficient for assimilation hazards of furniture and decorative materials.

Indoor air quality, depending on the concentration of carbon dioxide:

  • 1st class (optimum microclimate, high quality) – the concentration of carbon dioxide is not more than 400 cm 3 / m 3 ;
  • Grade 2 (optimum microclimate, average quality) – the concentration of carbon dioxide from 401 to 600 cm 3 / m 3 ;
  • 3rd class (permissible microclimate allowable quality) – the concentration of carbon dioxide from 601 to 1000 cm 3 / m 3 ;
  • 4th Grade – unacceptable high concentrations of carbon dioxide, poor air quality – more than 1 000 cm 3 / m 3.

The advantage of this approach to the definition of air quality and ventilation required in relation to the traditional (for specific air flow rate or ventilation rate) is as follows:


  • it is possible to take into account when determining the degree of ventilation of outdoor air pollution;
  • an incentive to increase the effectiveness of ventilation: supply of fresh air in the breathing zone, to avoid crossing the air-giving stream of dirty areas in the room;
  • can be accounted for the presence of fresh air in the room before filling in human beings;
  • can be well defined background ventilation to remove hazards from furniture and decoration materials after hours;
  • Improve the adequacy and accuracy of monitoring air quality at the expense of direct measurements of carbon dioxide concentration in the occupied zone premises.

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