The indoor air we breathe in on a daily basis contains more than just the oxygen we need, the air is polluted by people and their activities, furniture and building materials. One group of pollutants are the Volatile Organic Compounds (VOCs) and are mainly emitted by building materials. When the exposure to VOCs gets too high, there are significant health risks (cancer, non-hereditary asthma,…). Nowadays, buildings are fitted with a ventilation system to make sure the indoor air stays pleasant and healthy without losing to much energy. The new generation of ventilation systems, Demand Controlled Ventilation (DCV), can save even more energy by only supplying fresh air when it is needed based on CO2 and humidity measurements. In these systems the continuous emission of VOCs can be a problem because the air is not renewed continuously and thus VOCs can accumulate to high concentrations. In order to know if a certain ventilation system or system control can keep the indoor air healthy, a method to assess DCV systems is necessary. In this method, based on dynamic simulations, CO2, humidity and VOC concentrations should be estimated with good accuracy. Good models exist for CO2 and humidity but do not exist yet for VOCs. By examining literature, simulating and performing test facility measurements, this method for the assessment of VOC concentration will be developed and validated. Later it is applied on existing DCV systems and used in the development of new control strategies.