Volatile organic compounds (VOCs) or mixed gases are volatile organic compounds that evaporate easily and can have a significant impact on people's health and well-being. Known syndromes range from fatigue and headaches to eye irritation and dizziness. In contrast to the CO2 content in indoor air, most VOCs can be perceived by humans through their odor, although even 'pleasant' smelling VOCs can be potentially hazardous to health. Typical sources of VOCs include floor coverings and wall coverings, paints and adhesives, furniture and office equipment, but also plants, cleaning agents and perfumes.

Our AERASGARD air quality sensors measure the VOC content in indoor air using a measuring element that reacts to VOC molecules on its surface and has very low sensitivity to potentially disruptive influences such as temperature and humidity. The VOC load of the room air is output as a measured value for the room climate as a percentage. It is recommended to ventilate the room if the VOC level exceeds 60 %.

Carbon (carbon) dioxide (CO2) is a colorless and odorless gaseous compound of carbon and oxygen and is present in natural air at a concentration of around 0.04 percent (400 ppm). CO2 is released both when carbon-containing materials are burned and when we exhale. If the proportion of CO2 in indoor air is too high, both well-being and the ability to concentrate decrease. The CO2 content is also regarded as a surrogate indicator for the proportion of potentially virus-laden aerosols in rooms. Measuring the CO2 value therefore serves as a basis for a timely supply of fresh air to prevent these risks. The recommended threshold value for ventilation is 1000 ppm.
AERASGARD air quality sensors for CO2 work with a non-dispersive infrared sensor that uses the attenuating property of CO2 for light in the wavelength range of 4.26 µm to determine the CO2 concentration, see NDIR technology.

NDIR sensors for CO2 consist of a measuring system with a light source, a measuring path and a receiver with a filter. The filter is calibrated so that it only transmits light in the wavelength range of 4.26 µm, which in turn is typically attenuated by CO2 molecules along the measuring path. The sensor determines this attenuation and converts it into ppm CO2.

All AERASGARD air quality sensors for CO2 from S+S are equipped with a long-life NDIR sensor that automatically recalibrates itself at regular intervals to the basic value of 400 ppm (normal CO2 content in the outside air). They detect the CO2 concentration in the room air up to values of 3000 to 5000 ppm.

Since an NDIR sensor for CO2 selectively measures only the attenuation of light by CO2 molecules, it cannot detect VOC molecules. CO2 is an inorganic compound. A VOC sensor, on the other hand, only reacts to organic mixed gases and therefore does not detect CO2 molecules.

However, both values - the CO2 and VOC content - are usually decisive for a comfortable indoor climate. Approaches to converting or deriving the two values from each other have proven unsuitable in practice and are considered irritating. The AERASGARD range of air quality sensors from S+S therefore includes several multifunctional devices that are equipped with both an NDIR sensor for CO2 and a VOC sensor.

Dust is classified into standardized particle sizes as coarse, fine and ultrafine dust. Particulate matter (PM) is inhalable dust with an aerodynamic particle diameter of less than 10 µm. The international designation PM10 has become established for this. Respirable particulate matter is present from 2.5 µm or lower (PM2.5), and ultrafine particulate matter from 0.1 µm or lower.

Indoor particulate matter is produced by oil and wood heating systems, tobacco smoke and asbestos, filterless vacuum cleaners and toner for photocopiers or laser printers, as well as by fungal spores and plants. It can cause acute and chronic cardiovascular, cancer and respiratory diseases. A maximum 24-hour average value of 50 µg/m³ is prescribed for outdoor air in the European Union. Indoors, however, the values are often many times higher.

Several AERASGARD air quality sensors also have a fine dust sensor in order to incorporate fine dust pollution into the regulation of a controlled indoor climate that is as healthy as possible.