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Indoor air quality

Healthy indoor air and energy-efficient HVAC solutions

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We all spend a significant proportion of our lives inside, but how often do we consider the impact that indoor air quality (IAQ) has on our productivity, well-being or health? HVAC systems are frequently installed to help maintain the comfort levels of the building, but the health benefits for occupants and the energy efficiency of a development are usually less understood. Central air handling units (AHUs) can be used to address both sustainability and IAQ issues simultaneously. Belimo supplies a range of innovative solutions to optimize monitoring and control of HVAC systems and IAQ. Our framework, the Seven Essentials of Healthy Indoor Air, provides valuable information on how HVAC devices can contribute to IAQ in buildings without compromising energy efficiency.

We have summarised the topic with inputs from IAQ experts in a brochure. Enjoy reading:

General information about indoor air quality

Important indoor air quality indicators


Humidity is the measurement of moisture in the air, and should be maintained between 40-60 percent RH for optimal comfort. However, a humidity below this can cause drying of the skin, eyes or respiratory tract, while excessive humidity can facilitate mold growth. 

Carbon dioxide (CO2)

The indoor concentration of CO2 often correlates with the occupancy or activity level within an enclosed space. At a concentration exceeding 1,000 ppm, occupants will begin to experience a drop in productivity and, more importantly, may result in serious health complications.  


Temperature is often closely linked to humidity, and impacts overall well-being, productivity and health. The ideal room temperature is often subjective, but is also affected by activity levels, room occupancy, humidity and air velocity. 

Air velocity

Air velocity can greatly impact the temperature and comfort of indoor spaces, with greater velocity increasing the heat exchange between people and the surrounding air. In contrast, insufficient air flow can allow the build up of airborne contaminants, such as VOCs.

Volatile organic compounds (VOCs)

VOCs are organic, carbon-containing compounds that can evaporate at room temperature. There are many indoor sources of potentially harmful VOCs, including cleaning products, paints, softeners, printers and adhesives. 

Particulate matter

Microscopic solid or liquid particles can become suspended in the air from sources such as pollen, dust and mold spores. These fine particles can enter our lungs, causing allergic reactions, irritation or infections.


High-performing HVAC systems achieve a healthy indoor environment thanks to outdoor air supply, filtration, and humidity control. Contributing to IAQ is one of our responsibilities.
Lars van der Haegen
CEO Belimo

Your indoor air quality partner

Belimo promises to be a trusted indoor air quality partner, and supply reliable and energy-efficient HVAC solutions that provide comfort, safety and high quality system performance. We work together with our customers as a team to deliver results that meet the needs of every project – big or small. This collaborative approach is one of the many reasons we have become a trusted name worldwide, and a market leader in HVAC field devices.

Products for better indoor air quality

Ensuring the quality of indoor air requires a multipronged approach. Besides precise system design and regular maintenance, reliable products which can be seamlessly integrated into building management systems and IoT platform are essential. Belimo offers a complete and innovative range of HVAC control devices to maintain healthy indoor air quality without compromising energy efficiency.

Discover products for healthy indoor air quality:

Indoor Air Quality
Duct Sensors
Measurement of
Temperature, humidity,
enthalpy, dew point,
CO2, and VOC
  • Fast and error-free installation
  • High accuracy and fast reacting
  • Reliable and long-term stable
  • High robustness and NEMA 4X with
    IP65 protection rating
Shop Duct Sensors
Room Sensors Measurement of
temperature, humidity,
dew point, and CO2
  • Aesthetic design and outstanding
    user experience
  • Fast and error-free installation
  • Smartphone commissioning and
  • High accuracy and fast reacting
  • Reliable with long-term stability
Shop Room Sensors
Air Pressure Sensors
and Switches
Measurement of
differential pressure and
volumetric flow
  • Single & dual differential
    pressure sensors
  • Excellent zero-point stability
    and high accuracy
  • Auto-zero or manual calibration
  • Eight field selectable pressure
    ranges in one unit
Shop Pressure Sensors
and Switches
VAV Solutions Measurement and
control of
volumetric flow
  • Precise dP measurement and
    control of the smallest of
    volumetric flow
  • Smartphone commissioning
    and diagnostic
  • Compact or modular device
  • Seamless Building Management
    System integration
Shop VAV Solution
Damper Actuators Motorization of
air dampers
  • Comprehensive torque range
  • Low power consumption
  • Inputs for digitization of sensor
  • High robustness and up to
    NEMA 4X with IP66/67 protection
Shop Damper Actuators
Energy Valve Certified energy
measurement and
  • MID certified energy metering
    and pressure-independent flow,
    energy efficiency, power
    control and delta T management
    in once device
  • Digital commissioning workflows
    thanks to app and web tool
  • Patented glycol measurement
    and compensation or glycol
    alarm for MID versions
Shop Energy Valves

Success story

Effortless indoor air quality control with IoTs

Emch+Berger ImmoConsult AG, Zürich (Switzerland)

In 2020, real estate company Emch+Berger ImmoConsult AG needed a modern solution to control indoor air quality with HVAC systems in its brand new Zürich offices. Find out how Belimo’s HVAC components were installed with IoT support for hassle-free building automation, creating a comfortable working environment.


An individualised patient experience

University Hospital, Zürich (Switzerland)
In 2019, the University Hospital Zürich (UHZ) commissioned a temporary building with specialised burn wards. The organisation wanted to equip each room with separate control loops to allow individual adjustment of humidity and temperature to meet the needs of each patient. Find out how the installation of Belimo components achieved this under the time pressures and other challenges of a hospital setting.

The future of comfort in the virtual world

Liuzhou SoReal Spiral Paradise (China)

During development, the first virtual reality (VR) theme park in South China faced the challenge of maintaining indoor air quality for all visitors in its active arenas. Instead of calling game over, the company leveled up by installing over 100 Belimo sensors and energy valves as part of a state-of-the-art HVAC system, allowing system parameters to be adjusted to fluctuations in the volume of people and level of activity. This provided dynamic control of air quality, energy efficiency and thermal comfort throughout the building.


Most people spend approximately 90% of their time indoors, and breathe 12,000 liters of air per day. It is therefore important to understand the powerful influence that indoor air quality has on our wellbeing.

The "sweet spot" for indoor air humidity is 40 to 60%, as this dramatically reduces the transmission risk of diseases, and enables the body to better repair and protect itself.

At air humidity below 40%, the water droplets with viruses become smaller and can travel through large open office spaces and survive for hours. Furthermore, many bacteria and viruses become more virulent when exposed to dry air. If the indoor relative humidity is above 60%, mold and mildew begin to form and these can pose health problems.

CO2 concentration of more than 1000 ppm (parts per million) decreases the brain's ability to concentrate; starting at 2000 ppm and higher, it can lead to fatigue or even headaches. CO2 level in indoor air is an excellent indicator of space usage and occupancy and therefore an indirect way of potential bio-contamination, such as COVID-19 viruses. If the CO2 value is high due to increased occupancy and limited air exchange, there is a high potential risk from infectious aerosols.

As air circulation does not filter the air nor supply fresh air into the room, it is not a good solution either. On the contrary, strong unfiltered air movements further spread particles and pathogens within the space. A ventilation system with central air conditioning is needed to provide fresh, filtered, and conditioned air to the zones.

Air handling units usually supply air to several zones in a building. It is important that each room receives the exact amount of fresh air it needs. If the number of people in a room increases, e.g., in a larger meeting room, you would expect the air supply to increase accordingly. Similarly, the polluted air must also be removed from the room. To ensure this, zones and rooms must be supplied individually with variable air volume (VAV) based on air quality measurements.

The polluted and contaminated air must be removed from the room. It is important that each room receives the exact amount of fresh air it needs to prevent an increase in the concentration of infectious aerosols. To ensure this, zones and rooms must be supplied individually with variable air volume (VAV).

To prevent contaminants from entering indoor spaces through supply air ducts, suitable filters must be integrated into the air handling unit and must be replaced when the contamination of the filter increases. Pressure sensors and dynamic airflow measurements can be used to measure the degree of usage or contamination of the filters.

Central air handling units (AHUs) and air distribution systems can centrally control the quality of the supplied air at any time. Temperature, humidity, and air quality sensors permanently measure the conditions of the supplied air and deviations are instantly detected and corrected.

Indoor air quality can be measured either in the room or in the extract (return) air duct. Measuring the supply air doesn't reflect the indoor air quality situation in the room, but the fresh and conditioned air supplied by the air handling unit.

If the indoor air quality is measured in the room, attention must be paid to the mounting location to ensure proper and correct measurement. The installation should be at a height of around 1.5m (5 feet) and at least 50cm (20 inches) from the adjacent wall. It should not be exposed to direct sunlight nor mounted on external walls. Furthermore, avoid installations above radiators, directly adjacent to doors, in recesses (e.g. shelves) and behind curtains.

Alternatively, the measurement can take place in the duct which extracts the used air from the room. While the correct placement of a room sensor requires more attention, the advantage over a duct sensor is that, thanks to its exposure to the occupants, it allows direct, visual, thermal and indoor air quality feedback by means of a display or a traffic light indication.

In systems with variable air volumes for demand-controlled ventilation, the differential pressure fluctuates according to the airflow. In this situation, a pressure switch is not suitable for monitoring the filter status; a differential air pressure sensor is the solution. Air pressure switches are a cost-efficient and reliable way to monitor filters in systems with constant air volume flow.

Join our indoor air quality training and webinars

The objective of our HVAC webinars and training programs is to further educate seasoned service technicians, facility managers, distributors, control contractors, and building owners on IAQ real-world problems and solutions as well as the importance of occupancy health and efficient system performance. Our offerings are organised and held worldwide.

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