E&S GALLEY PROOF 1 © Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin · Bauphysik 31 (2009), Heft 5 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 be- longing 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 opti- mal concentration levels of carbon dioxide (CO 2 ) 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 deter- mination of the percent value of users unsatisfied with the air quality in relation to the mean concentration levels of CO 2 . 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 CO 2 and TVOC (Total Volatile Organic Compounds) sensors. As the most relevant result it can be noted that, as long as the CO 2 concentration levels do not rise above 1,200 ppm, the users are incapable of discerning any decrease in air quality of the workspace. The minimum percentage of dis- pleased users about air quality is about 30 %. Luftqualität in Bürogebäuden auf Basis von Messungen und Nut- zerbefragungen. Zur Sicherstellung einer optimalen Lüftung von Arbeitsräumen ist der Planer in Deutschland zur Einhaltung der strengen Anforderungen an die Luftqualität aus DIN EN 13779 ge- zwungen. In der vorliegenden Arbeit wird vor Ort eine umfangrei- che Untersuchung von 270 Arbeitsräumen in 30 Bürogebäuden durchgeführt. In Bezug auf die Luftqualität wurden zwischen der Richtlinie und dem Nutzerempfinden deutliche Unterschiede fest- gestellt. Der Zweck der Untersuchung ist die Definition der opti- malen Konzentration von Kohlendioxid (CO 2 ) auf Grund des Ver- gleichs zwischen objektiven Daten von Messungen und subjekti- ven Daten aus der Befragung der Nutzer von Arbeitsräumen. Die Bewertung der Luftqualität mit Hilfe der Norm und des mittleren Votums der Nutzer ermöglicht die Bestimmung der prozentualen Nutzerunzufriedenheit mit der Luftqualität in Abhängigkeit von den durchschnittlichen CO 2 -Konzentrationen. Die Untersuchung besteht aus der Auswertung kurzer Fragebögen und Messungen mit einer mobilen Einheit, die mit CO 2 - und TVOC-Sensoren (Total Volatile Organic Compounds) ausgestattet ist. Als wichtigstes Er- gebnis kann festgestellt werden, dass solange die CO 2 -Konzen- tration nicht über 1.200 ppm steigt, die Nutzer nicht in der Lage sind, eine Verringerung der Luftqualität in den Arbeitsräumen zu empfinden. Der geringste Anteil der auf Grund der Luftqualität unzufriedenen Nutzer liegt bei 30 %. 1 Introduction In Germany, the evaluation of air quality is supported by setting limits to the concentration of carbon dioxide (CO 2 ), as proposed by the standard [1] originated in [2]. In addi- tion to this gas, there are substances in the form of gases combined with dust and particles suspended in the air, na- mely, the Volatile Organic Compounds or VOC, which can adversely affect the air quality and become a hazard to the health. Possible sources may be found in the materials used in construction, the furniture and office equipment, the low ratio of air replenishment and circulation, the ac- tivities of users (e.g., hobbies), the emission of biogases, ci- garette smoke and, in some instances, the external air [3]. The summation of all organic substances suspended in air is known as the Total Volatile Organic Compounds (TOVC). Until present there is neither an exact definition of TVOC nor quantitative results to allow determining the hazard levels posed by the concentrations. The users of workspaces are not passive subjects in regards to the air they have to breathe. Therefore, it is nor- mal that they react to changes in air quality in ways simi- lar to changes in weather, for example, by adapting their clothing, opening or shutting windows, or using shading devices against strong solar radiation [4]. In general, these variations are sensory perceptions of the individual. How- ever, there are gases and substances that are not perceived when they occur at low concentrations, yet they may pose some risk to the user‘s health, as stated by [3]. The CO 2 and TVOC parameters are capable of affecting the con- centration and overall efficiency of users in a work space. On these accounts, the level of ventilation or air change rates within an indoor space could be considered a varia- ble of economic type [5]. The purpose of this air quality evaluation method for office buildings is to obtain a survey focused on the condi- tions of real workspaces and the perceptions of users on the air quality of those spaces. The method is based on a series of measurements taken with a mobile device featur- ing several sensors along with the simultaneous answers of air-quality questionnaires responded to by the users. They submit their votes on air quality and respond about the in- fluencing factors (weather-related and other causes) that affect their workspaces [6]. For the analysis, a database is built on information from 270 workspaces and the diagno- sis of 1095 air quality votes surveyed from 30 office build- Indoor air quality defined by measurements and questionnaires in office buildings Ernesto Kuchen M. Norbert Fisch Marlon Lea ˜o Érika Borges Lea ˜o Fachthemen Bauphysik /2009  druckfrei  nach Korrektur druckfrei Aufsatz-Nr. 713 Datum, Unterschrift DOI: 10.1002/bapi.200910000