The CO2 meter: an essential ally to ensure air quality

A CO2 meter is a device specially designed to monitor the air quality in indoor spaces of a building. Maintaining adequate indoor air quality is not only essential to avoid the sick building syndrome, but also to create pleasant indoor environments that do not endanger the well-being or health of its occupants.

Regulations and air quality

According to current regulations (CTE DB HS 3, Indoor air quality), it is mandatory to provide indoor spaces with a minimum ventilation flow that ensures proper air renewal. Thus, fresh, clean air free of impurities must be supplied indoors while expelling the contaminated air due to the regular use of the premises by users.

It should be noted that the minimum air flow must vary depending on the occupancy of the spaces, so it is vital to have ventilation systems that allow for the regulation of the ventilation flow that is desired at any moment. A good solution is self-regulating extraction vents, which allow the user, through automatic air flow demand control devices, to decide at all times the amount of m3/h that they wish to extract.

The contaminating particles that the air can carry are mainly CO2 resulting from the respiration of living beings and volatile organic compounds emitted by the construction materials themselves (paints and other chemical products from the materials).

How does a CO2 sensor work?

A CO2 sensor, installed in tertiary use buildings (offices), is a presence detector connected to the ventilation system to regulate it according to the level of contamination to which each of the spaces is subjected. Considering that the maximum occupancy rate during a working day of the rooms in an office building does not exceed 60%, this is an ideal energy saving measure.

There are two types of sensors available in the market:

• Monozone: the space to be ventilated is not compartmentalized. • Multizone: the space to be ventilated is compartmentalized, but the air renewal must be homogeneous.

According to the levels of contamination (based on the CO2 rate resulting from the metabolic activities - respiration - of the users), the device will order to increase or decrease the speed of the extractor to adjust the minimum ventilation flow according to the needs of each moment.

Installation of measuring probes

The probe should be installed either on a wall of the premises or in the extraction network.

If the probe is installed on the wall of the premises:

• It should be positioned at a height of between 1.5 and 3.5 meters from the floor. • Air currents should be avoided (windows, doors, supply vents) and dead spots (drawers, shelves, curtains). • Heat sources and proximity to occupants should be avoided (they should be located within a radius of 1 to 2m from a workstation).

If the installation of the probe is done in an extraction duct:

• The extraction opening should be located at least 3.5 meters high and should be more than 6 meters away from the CO2 sensor. • A hole should be made in the duct on the lower side of the diameter of the sensitive element of the probe, the probe should be inserted into the duct, ensuring good airtightness around it, and the probe should be secured with 2 screws using the mounting brackets.