Indoor air quality

CO2 sensors for energy savings and better health


Indoor air quality - monitor and control with CO2 sensors

By measuring the CO2 level, you can regulate the air flow according to need. With demand controlled ventilation you can improve health, prevent the spread of virus and reduce energy costs with up to 50%. By using a self-calibrating sensor, you can mount and forget your sensor for the next 15 years and it will still be accurate.

Good ventilation has become a necessity. Studies show that we spend over 90% of our time indoors. How do we find the perfect balance between money spent on ventilation, versus health and productivity levels affected by bad air quality, which also helps the spread of viruses. You will find our sensors in residential, commercial, and official buildings.

Did you know?

  • At 0,15% CO2 you start feeling tired.
  • At 0,25% CO2 you make 31% more mistakes according to a Harvard study on pilots.1
  • At 0,3% CO2 every 18th breath you take is reused air. How is that from a contagion perspective?
  • Headache, brain fog, tiredness and shortness of breath are all warning symptoms of a too high CO2 level.


Pär Nordin

Pär Nordin

Executive Sales Director

+46 653-71 77 83


Learn More About Indoor air quality

Productive and healthy indoor air quality

The more people in a building, the more CO2. By measuring the CO2 level, you can regulate the airflow according to need. This will save energy and create a healthy indoor environment.

Key benefits of good indoor air quality:

  • Increased productivity level
  • Better decision making performance
  • Long-term health benefits

Building Management Systems

The primary indoor source of CO2 in office buildings is the breathing of the building’s occupants. CO concentration in office buildings typically ranges from 400 to 2,500 ppm. With CO2 measuring, it is possible to control individual fans, dampers, valves etc., which create a better indoor environment and energy savings. A common application is controlling ventilation in rooms with varying numbers of people, such as offices, classrooms, and cinemas. 

Indoor air quality also improves due to a reduction in the number of viruses and bacteria. Ventilating a room also reduces the number of particles occurring indoors. 

World Health Organization

In the publication “School Environment: Policies Current Status”, the World Health Organization (WHO) states that good indoor air quality, where carbon dioxide is one of the focus areas, is the basis of lower rates of absenteeism among students and teachers, stronger academic performance, better teacher retention and job satisfaction, cost savings in many areas including building maintenance, and less sick leave.

You can also read a thought-provoking article about a study done on the air quality during Thanksgiving in The New Yorker.

Safety and decision making performance

Health and safety are about short- and long-term effects. There is a debate about how CO2 affects our health, but there appears to be a consensus that levels above 2,000 ppm disturb our wellbeing and efficiency, levels above 5,000 ppm are hazardous, and 10,000 ppm is life-threatening.

The latest research is conducted at NASA, where there has been a thorough health control of the astronauts working on the International Space Station (ISS). 

Another clinical study, done on Earth, shows that on nine scales of decision-making performance, test subjects showed significant reductions on six of the scales at CO2 levels of 1,000 ppm and large reductions on seven of the scales at 2,500 ppm.

The most dramatic decline in performance, in which subjects were rated as “dysfunctional”, was when taking initiative and thinking strategically. “Previous studies have looked at 10,000 ppm, 20,000 ppm; that’s the level at which scientists thought effects started,” says Berkeley lab scientist Mark Mendell, co-author of the study, “that’s why these findings are so startling.”

Read the full study here:

Saving energy with demand controlled ventilation

In a commercial building, the number of people visiting can vary greatly. If you need to heat or cool the building, you can save a large amount of energy by changing the airflow according to demand.  

Key benefits:

  • Energy savings
  • Positive environmental impact
  • Healthy indoor air quality

The CO2 concentration in a room varies depending on the number of people in it.  An empty room generally has a concentration of about 400 ppm (normal outdoor concentration). The CO2 concentration in the room will then increase for each person added.

Therefore, a small Demand Controlled Ventilation system can be a good idea. This system has a sensor that measures the CO2 value and sends a signal to a ventilator or a VAV-device that then changes the level of ventilation required in the room. The system also has variable dampers that are usually used to regulate the airflow through the sensor.

A minor ventilation system is an intelligent sensor or analyser that is adjusting one fan in the same room. This fan regulates the airflow.

Reduced costs

This application saves a lot of money in the form of energy savings. Room fans will only operate for as long as they need to, based on the level of CO2 in the environment. This reduced use of energy is also good for the environment and is an obvious way to conserve the earth's resources.  

Tests on buildings that are using Demand Controlled Ventilation show that energy costs are reduced by about 30%. This can lead to a return on investment in about 1 year.


How much can we save with CO₂ solutions?

Ventilation control is one of Senseair's major markets: you will find five million of our sensors in different locations around the world!

In a commercial building, the number of people visiting can vary greatly. If you need to heat or cool the building, you can save a large amount of energy by changing the airflow. Your choice is fixed or demand control (in our case COlevel).

Reference case

One example is the Swedish Government's chain of liquor stores, who installed our CO2 sensors with an automated airflow system in all their stores. Within ten months, the investment was paid, and after that, it is a saving, both economically and environmentally.

In the 13 countries participating in the IEA Energy Conservation in Buildings & Community Systems Program, the primary energy consumption attributable to the ventilation of all buildings is estimated to equal 9% of the total primary energy consumption of the countries.

An estimated 3 exajoule (EJ) of energy are used annually to ventilate US residential buildings, approximately 30% of the total energy used in these buildings. In the US service sector (e.g. commercial, institutional, and government buildings), the estimated energy consumed for ventilation is 1.5 EJ, approximately a quarter of total service-sector building energy use. The annual carbon dioxide emissions attributed to ventilation are approximately 1,000 and 800 million tons for the US residential and service sectors, respectively.

Climate has a large influence on the energy required to thermally condition ventilation air. In Europe, most of this energy is used for heating the ventilation air. In the US, significant energy is used both for heating and cooling. In the humid Miami climate, 86% of the energy is used to remove moisture from the ventilation air.* 

*Seppanen, O (2002). "Ventilation, Energy and Indoor Air Quality".


Calculate ventilation in a room with varied population

Residential, commercial, and governmental buildings have become the biotopes in which we spend most of our time. We live, eat, exercise, and work mostly indoors.

Since we exhale carbon dioxide (CO2), good ventilation is a necessity. CO2 can be dangerous in high concentrations and will affect our productivity level and decision-making performance at levels lower than previously thought. 

Open the windows, please!

How hard can it be? We used to live and work in houses with a natural draft. When the energy crisis made us aware of the cost of burning fuel, we started to make denser walls, windows, and doors. This, in turn, created new problems with moisture, Sick Building Syndrome, and bad air quality. As we started craving good air quality and a safe environment, we started working with controlled ventilation.

If we calculate the ventilation needed in a small room, we can start with the need for one human being. The normal calculated value is 10 litres/s. From that, it is possible to estimate the number of occupants multiplied with the minimum rate required in your country (e.g. 7 litres/s). 

But how do you calculate the need for a courtroom, a store, or a movie theatre? If you calculate for the maximum amount of occupants, energy will be wasted when the room is empty.

If we apply a sensor that measures CO2, we can regulate the amount of air needed. With a pitot tube (the same tube that is used on aerplanes to measure speed by airflow), we can measure the amount of air provided.

A fan can produce a pressure in the air channels (i.e. 10 Pa) and the sensor regulates a damper.

It is not the sensor that is the brain of the system: our OEM customers apply logarithms and other means of control to make a system reliable and suitable for your application.

You might interject that air quality is not only about CO2 (the odourless gas that becomes dangerous at levels around 5,000ppm and above), and you are correct, but research* has shown that an adequate airflow measured with CO2 also reduces the risk of other problems.

* "Association of Ventilation Rates and CO2 Concentrations with Health and Other Responses in Commercial and Institutional Buildings", by Seppanen, O.A., Fisk, W.J., & Mendell, M.J. (1999).

IoT and sensors

When it comes to measuring air quality, sensors play a major role as they perceive the information faster than our brains. The sensors become our 6th sense. 

Key benefits of a connected CO2 sensor:

  • Remotely monitor the indoor air quality
  • Simple installation to a low cost – no wires are required
  • Get control of the entire property’s air quality in one single place – the dashboard – from your laptop or cell phone. Anytime. Anywhere.
  • Save time and resources by only inspecting and adjusting actual problem areas, not all areas
  • Alerts when adjustable thresholds are reached
  • Works independently of the building’s HVAC system
  • Possible to create your own customized dashboard using the API
  • Maintenance free with a battery life time of minimum 5 years

The IoT revolution has increased the demand to monitor and control our environment. We want everything to be automated, but no setting more than a touch screen away.

Air purifiers and CO₂

Air purifiers are becoming extremely popular in areas where the outdoor air quality is troublesome or even hazardous. In order to keep the polluted air outside, people are forced to keep all the windows and doors closed, which of course affects the inside air quality. The problem with purifiers is that even though they will remove the contaminants, the CO level will rise to dangerous levels. Serious purifier manufacturers will let you know.

If you are a developer looking for a reliable sensor, please look at our Sensor Core and what comes with it; a self-calibrating sensor will add value and reliability to your product!

Technical application

There are chiefly two options regarding where to install sensors: in a room close to the occupants or in the ventilation system to detect the CO level on outflowing air. How you choose to place your sensor depends on the nature of the space.

Let’s use a hotel as an example. In the restaurant or a big lobby, a sensor on one wall would most probably misread the other side of the room, so a sensor in the outgoing air might make more sense. In a small conference room or a regular hotel room, a sensor on the wall is sufficient.

There is also a difference between CO and temperature sensing and control. The temperature is quite even throughout a room. CO₂ levels, on the other hand, can vary from 3,000 ppm on one end of the room to 600 ppm on the other.

When installing sensor-controlled ventilation, there are a variety of strategies and algorithms to choose from. Depending on who you are (an OEM developer, a system developer, a distributor), we need to discuss what strategies you want to apply.

A sensor will deliver a signal strength depending on CO2 variables. The frequency of measurements depends on your needs and energy savings. 

Here are some different strategies:


Most likely, our sensors end up in PID controlled systems (for more information on PID, see below), as they are suitable in multi-zone buildings that have high variables and unpredictable patterns of occupancy.

Helpful links ("PID for dummies"):


CO2 controls the damper with a set point and when ventilation reaches the correct level, the sensor closes the damper. This strategy works well in applications like schools, theatres, and conference rooms where the occupancy can vary greatly from one minute to the next.


This strategy works with the difference between outside and inside air. For example, the setting point can be 100 ppm over outside level. When the desired CO level is reached, the control eases up on “the gas pedal”.

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