Indoor air quality defined by measurements and questionnaires in office buildings

The need for optimal ventilation of office spaces in Germany compels the designer to respect strict requirements on air quality as stated in the German Standard DIN EN 13779. In the present field work, an extensive survey is made in 270 work spaces belonging to 30 office buildings of various German cities, in which notable differences have been observed between the lineaments of the norm and the diagnosis issued by the users in regards to air quality. The purpose of the present work is to define the optimal concentration levels of carbon dioxide (CO₂) on the basis of comparing the objective date obtained through measurements and the subjective data collected with a questionnaire responded to by the space users. The evaluation of the air quality level using the norm's criterion and the mean vote of users allows the determination of the percent value of users unsatisfied with the air quality in relation to the mean concentration levels of CO₂. The research method consists of user inquiries, in the form of a short questionnaire, while making brief measurements on site with a mobile unit equipped with CO₂ and TVOC (Total Volatile Organic Compounds) sensors. As the most relevant result it can be noted that, as long as the CO₂ concentration levels do not rise above 1200 ppm, the users are incapable of discerning any decrease in air quality of the workspace. The minimum percentage of displeased users about air quality is about 30 %.