Carbon Dioxide CO2, Volatile Organic Compound VOC & Particulate Matter Sensors & Air Flow Monitors


‘Feel-Good Climate’ with Energy Efficiency

Air, Gas & Liquid Control with Measuring Devices from S+S

Our Sensors for Air Quality and Flow

Increased indoor CO2 values, fine dust (PM) or VOC loads are bad for
energy efficiency and well-being. With our AERASGARD® air quality and
RHEASGARD® ­flow sensors you can monitor the entire room climate in a
controlled way. And with our RHEASREG® air flow monitors and flow
measuring transducers you are well in control of ducts for air, gases or liquids.

Application Areas of Air Quality Measuring Devices

Room ventilation and air-conditioning, flow monitoring of ventilators,
butterfly valves, heating registers and humidifiers, energy management, residential, working and conference rooms, movie theatres, showrooms
and retail stores, institutes and laboratories


  • High energy saving potential
  • Enhanced comfort and well-being
  • Available in many different versions
  • Multi-functional devices for up to
    4 measurands
  • Patented multi-chamber channel pipe
  • Interconnective Modbus versions
  • Optionally with M12 connector
Plug & Play

CO2 Traffic Light with Acoustic Alarm

Against Fine Dust (PM)

Particulate Matter Sensor Devices

Ambient Air Quality Control:

Make Room Climate Measurable

The room climate has a significant influence on well-being, productivity and energy efficiency. Our multi-functional room sensor devices provide you with data about the most important measurands of humidity, temperature, mixed gases (VOC), CO2 and particulate matter. Active and Modbus capable transmitters available.

  Purchase room climate sensors here

Assured precision

The air flow monitors are tested according to the latest criteria. Take advantage of our experience, our development, manufacturing and product know-how and order these products directly from the manufacturer


Broad spectrum

Our active air flow monitors for measurement and control of CO2, gas mixtures (VOC), particulate matter (PM) and flows are designed to be multifunctional. This reduces the diversity of types and expands their possible applications. Thanks to microprocessor technology, almost any measuring range can be represented, including customer specifications. DIP switches are used to select functions such as multi-range switching, automatic mode, and manual calibration.

Measuring method and compensation of atmospheric pressure

Due to ever-increasing demands on precision, maintenance-free operation and long-term stability, we have further developed and improved the proven switchable measuring system. The new generation of instruments now features a dual-beam measuring method and compensation of the atmospheric air pressure for CO2 measurement.

Single-beam measuring method

The single-beam measuring method is particularly suitable for applications where rooms to be monitored are temporarily unoccupied. A prerequisite for a reliable measurement result is a regular supply of fresh air – at least three times in seven days. This is the most common application.

Dual-beam measuring method

The dual-beam measuring method consists of a reference and a measuring channel. Here, the reference channel operates in a spectrum that is not influenced by the CO2 concentration of the medium. Ageing, contamination and drifting affect both channels. The above-mentioned phenomena can be largely compensated for via these connections, without having to rely on a supply of fresh air. The dual-beam measuring method is always used when the application involves exceptional circumstances – for example, rooms that are used 24 hours a day, 7 days a week without interruption.


Up to now, there has been no compensation for the influence of atmospheric air pressure in building automation. Low and high-pressure weather conditions as well as pressure influences from high altitudes result in air pressure fluctuations of up to ± 100 mbar. In uncompensated systems, it results in measurement errors of up to ± 16 % of the measured value. The new generation of our air flow monitors integrates the measurement of the atmospheric air pressure and corrects the CO2 value accordingly.
From S+S Regeltechnik, you can get air flow monitors for CO2 or VOC in various designs and, as a significant difference to other manufacturers, even combined CO2 and VOC devices using separate sensors for these two measurands, including switchable measuring ranges. The key element in demand-controlled ventilation is the overall indoor air quality, often referred to as the comfort zone. In addition to the known and accepted control variables, such as relative humidity and temperature, even the CO2 and VOC content of the air are important control variables. Every person interprets indoor air or its quality differently. For this reason, it is only possible to give a general definition.
The air must be perceived as pleasant by the majority of people and not cause them to feel uncomfortable. No pollutants in hazardous concentrations must be present in the air. In this case, only the opinions of the people entering the room are valid, since people become accustomed to their surroundings and thus to various pollutant loads, i.e. they no longer perceive them. An important task of systems for demand-responsive, energy-saving ventilation is to ensure good indoor air quality.

Carbon dioxide

A measuring system based on NDIR (non-dispersive infra-red technology) for CO2 measurement consists of a light source and a receptor. A specific range of wavelengths of light radiated by the source is attenuated and absorbed by CO2 molecules in the measured section. This attenuation is detected by the receptor. In building automation, the detection of the CO2 content is primarily used to monitor non-smoking rooms with varying numbers of people, such as conference rooms, break rooms, cinemas, schools, etc. In this case, the person-related increase in CO2 content is interpreted as a "deterioration" of the air. In recent years, a standard measuring range of 0...2000 ppm (parts per million) has become established for CO2 measuring instruments. Although this measuring range covers the recommended maximum CO2 concentrations for work and living rooms (1000...1500 ppm), practical experience has shown that in many applications the measuring range of 2000 ppm is not sufficient. We have therefore developed and introduced a new generation of instruments with switchable measuring ranges of 2000 ppm and 5000 ppm.



How does an air flow monitor work?

VOC is the abbreviation for Volatile Organic Compounds. According to the definition by the World Health Organisation WHO, VOCs are organic substances with a boiling range from +60 to +250 °C. Examples of VOCs include compounds of the substance groups alkanes ⁄ alkenes, aromatic compounds, terpenes, halogenated hydrocarbons, esters, aldehydes, and ketones. There is a large number of naturally occurring VOCs, some of which are also released into the atmosphere in substantial quantities, such as terpenes and isoprene from forests. The environmental impact of VOCs caused by human activities has increased sharply in the last century. The largest share of this is accounted for by transport, but the construction sector is already in second place with construction chemicals such as paints, adhesives or sealants. Possible sources of indoor VOCs include not only building materials but also furnishings, cleaning and maintenance products, hobby and DIY products, office chemicals, and especially tobacco smoke. Carpets are a major source of VOCs. VOC-related odour problems can also be microbial, caused by metabolic substances from bacteria and fungi. It is precisely these listed substances or their increased occurrence that should be determined. Since the air to be monitored contains a large number of substances to which the sensor reacts and gas mixtures are produced, this sensor does not act selectively but reflects the general air quality. In principle, it is also not possible to state precisely what is "bad air" or what is "good air" because this is a purely subjective perception. Ventilation is recommended starting from a value between 60 - 80 % VOC. The sensor changes its conductivity depending on the concentration, type and mixing ratio of reducing molecules in the ambient air.


What is the difference between CO2 and/or VOC air flow monitors?

The versions listed above show that there are applications for CO2 measurement and for VOC measurement, but from our perspective primarily for a combination of both measurands. It is important to note that both of these measurands cannot be converted into each other or derived from one another. An NDIR CO2 measuring instrument measures selectively and cannot detect any VOCs, a VOC mixed gas sensor cannot detect CO2 molecules. The new duct sensor in the Tyr 2 housing design with PLEUROFORM™ multi-duct tube masters this separation perfectly, can detect both CO2 concentration and VOC mixed gas (or gas pressure) and, as a true multifunctional device, also supplies humidity and temperature data if necessary.