Specifications S14 - Commissioning-hvac.org

1 Description of the considered object
This specification concerns the air quality sensors installed in the building and in the HVAC
systems. A more general information about sensors validation is given in generic FPT,[12], to
which an automatic reference is done whenever required.
1.1 Operating principles
Two types of pollutants are generally measured in building and HVAC systems: the CO2 and
VOC ( volatile organic compounds) sensors.
1.1.1 CO2 sensors
CO2 is not a pollutant as such, provided it remains in the acceptable range. The CO2
concentration is nevertheless a good indicator of the occupancy rate, as well as of the activity
level in a room or in a building. CO2 sensors are usually measuring the absorption in a part of
the infrared range by the measured gas. Thermal energy associated to the absorption process
is proportional to the gas concentration.
Figure 1 gives the rates of CO2 generation for several activities, [11].
Figure 1: Rates of CO 2 generation for various activities
The rate of CO2 production varies with diet and health, as well as with the duration and
intensity of physical activity. The more exertion an activity entails, as measured in metabolic
equivalent task (MET) units, the more carbon dioxide is produced [11].
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