CO2 and VOC sensors in demand controlled ventilation (DCV) system
July 8, 2014

CO2 and VOC sensors in demand controlled ventilation (DCV) system

Background information on CO2 and VOC

The lethal level of CO2 is 100,000 ppm (10%). The CO2 level of 25,000 ppm (2.5%) can cause a severe headache. And maximum control value of CO2 in Swedish buildings is 1,000 ppm. The toughest regulation for ventilation is in a submerged submarine where the maximum allowed level of CO2 is 15,000 ppm in a war time (source Karolinska Institute, Sweden).

The most allergic reactions (called anaphylaxis) are from a sting from wasp (1st place), odour (2nd place) and peanut substance (3rd place).

Indoor air contamination in buildings

There are two sources of indoor air contamination: human being and building materials including furniture, office equipment and consumer products). To get rid of VOC from building materials one needs to have a permanent ventilation of 5-10% of building volume. Demand controlled ventilation can be used to get rid of VOC from human beings in a controllable and manageable way. For example, a strong perfume consists of 95% of alcohol and this can be detected by VOC.

Zero level for VOC and demand controlled ventilation

After approximately 6 months (or one year) of full ventilating of a building to phase out the emissions in a new building, one can find the level of stabilized VOC particles. This level can be established as a new zero level for VOC particles and then the demand controlled ventilation system will ventilate a building based on the particles above this level.

In Sweden, the minimum ventilation level required by the building regulation is 0.35 l/s per m2. If the VOC sensors could be used there would be a possibility to reduce the hygienic airflow down to 0.15 l/s per m2.

As for today, the most used sensor is CO2 sensor. The research shows that the measurements obtained from CO2 and VOC measurement correlated very well but CO2 sensor does not detect the spikes in various particles as the VOC sensor does. The VOC sensor costs 1/4 of CO2 sensor.