Low-cost sensors measuring volatile organic compounds (VOCs) can be of interest for reducing energy use for ventilation in buildings and maintaining good indoor air quality. However, the accuracy of many of these sensors remains unclear. This study aims to evaluate four different VOC sensors available on the market by exposing them to known concentrations of the VOC-gases in ISO 16 000-29: m-xylene and n-octane (mixed), alpha-pinene, and methyl-isobutyl-ketone (MIBK). The VOC sensors tested were metal oxide semiconducting sensors, and two copies of each sensor were included. Results show that all four sensors did not respond to every test gas. Moreover, two copies of the same sensor did not give the same output. Further, the output from the different sensors varied considerably. For the reference 110 ppb alpha-pinene, the sensors output varied from 810 to 1650 ppb. Reference concentration for MIBK: 180 ppb with sensor output: 230-1040 ppb, and reference concentration for mixed gas: 100 ppb with sensor output: 220- 730 ppb. Although the results seem discouraging, several of the sensors did respond to changes in concentration of the test gases and thus might be used for ventilation control purposes. Nevertheless, there is a need to evaluate and verify VOC sensors before using them for control of IAQ.

Buildings are constructed and operated to satisfy human needs and improve quality of life. Good indoor air quality (IAQ) and thermal comfort are prerequisites for human health and well-being. For their provision, buildings often rely on heating, ventilation, and air conditioning (HVAC) systems, which may lead to higher energy consumption. This directly impacts energy efficiency goals and the linked climate change considerations. The balance between energy use, optimum IAQ and thermal comfort calls for scientifically solid and well-established limit values for exposures experienced by building occupants in indoor spaces, including homes, schools, and offices. The present paper aims to appraise limit values for selected indoor pollutants reported in the scientific literature, and to present how they are handled in international and national guidelines and standards. The pollutants include carbon dioxide (CO2), formaldehyde (CH2O), particulate matter (PM), nitrogen dioxide (NO2), carbon monoxide (CO), and radon (Rn). Furthermore, acknowledging the particularly strong impact on energy use from HVAC, ventilation, indoor temperature (T), and relative humidity (RH) are also included, as they relate to both thermal comfort and the possibilities to avoid moisture related problems, such as mould growth and proliferation of house dust mites. Examples of national regulations for these parameters are presented, both in relation to human requirements in buildings and considering aspects related to energy saving. The work is based on the Indoor Environmental Quality (IEQ) guidelines database, which spans across countries and institutions, and aids in taking steps in the direction towards a more uniform guidance for values of indoor parameters. The database is coordinated by the Scientific and Technical Committee (STC) 34, as part of ISIAQ, the International Society of Indoor Air Quality and Climate.