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COMo – CO2 monitoring in publicly accessible indoor spaces

Illustration of the COMo Widget

Illustration of the COMo Widget

In COMo, the CO2 concentration (CO2 = Carbon Dioxide) serves as a measure for indoor air quality and aerosol pollution; the latter correlates with the potential (COVID) viral load. Objective CO2 readings via networked sensors enable operators to control the indoor air quality and thus reduce the risk of infection for visitors. Published data allow visitors to make decisions about visiting the facility.
All content is available under open source licenses (MIT, BSD, Creative Commons).

Innovation Summary

Innovation Overview

What problem does the innovation solve? During the SARS-CoV-2 pandemic, operators of publicly accessible spaces experienced a significant drop in visitors, educational institutions and cultural institutions had to limit their operations or completely shut them down. To enable an improvement or even a return to normal operation, we have developed an IoT project to control indoor air quality. As we spend 80-90% of our time indoor, air quality control is important. Poor indoor ventilation causes headaches, fatigue and dissatisfaction. With the SARS-CoV-2 pandemic, there is another reason for indoor air quality monitoring: Corona viruses are mainly transmitted via virus-containing aerosol particles that spread through the air. Further, studies show that the CO2 concentration in the room can be used as an indicator for aerosol pollution. Proper ventilation is a good measure to minimize the risk of infection and improve air quality. Since CO2 is odourless, it is therefore advisable to monitor the concentration in the interior using specific sensors and to execute ventilation of the rooms according to these measured values. We are guided by the legal regulation that concentration values below 1,000 ppm in the room air are considered harmless, from 1,000 ppm ventilation measures should be checked and improved and from 2,000 ppm the room air is considered hygienically unacceptable.

Our project uses the CO2 readings to provide operators and potential visitors to a location with information about the air quality there. For this purpose, the data from the on-site sensors is transmitted to our servers via LoRaWAN radio via special gateways. From there, the operators of the premises can call up the data. To give a quick overview of the current air quality, we visualize the sensor data as a value on a color scale ranging from blue (good air quality) to red (poor air quality). These sensor values are publicly visible on the COMo website, provided that the operator of the location has agreed to this. All content of the project is under established Open Source licenses (MIT, BSD, Creative Commons), the source code of the visualizations is provided to the state of Berlin and its institutions free of charge and freely licensed in order to further develop the project.

The pilot project aims to provide information about:

  • How the sensors can be optimally used for monitoring the interior.
  • Whether the provision of the data leads to a change in the behavior of operators and visitors.
  • Whether the LoRaWAN technology used enables data transmission that is sufficiently secure and sufficient for data evaluation and the forecasting of ventilation measures.

Who benefits from the innovation? The project has provided insights that enable further expansion of the monitoring of CO2 readings to improve indoor air hygiene. Around 50 sensors as well as indoor and outdoor gateways were installed in various institutions. Easy-to-understand visualizations of the measurements were developed and implemented on the project website. The project results will be made available to the Berlin Senate.

  • The visualization of the sensor values is intended to enable the operators of the respective premises to have active ventilation management in order to always keep the air quality within a hygienically safe range.
  • By making up-to-date data publicly available, the operator can demonstrate that it pays attention to the well-being of its visitors.
  • Thus, it is possible for potential visitors to check the air quality on site before a visit and to control the time of the visit
  • Finally, the federal state of Berlin receives information on how the LoRaWAN infrastructure needs to be expanded in order to offer a secure platform for environmental sensor data in an IoT scenario. By using open standards and free licenses, Berlin can access the entire project results without restrictions.

How is the innovation envisioned for the future? For example, how will it be institutionalized in its current context? How will it scale even bigger? It is planned to use findings from the pilot project in a follow-up project and to use them on a larger scale:

  • Operation on a larger scale in public buildings in order to evaluate the forecast of ventilation intervals based on the measured values
  • Expansion of the LoRaWAN infrastructure in a defined area to ensure the transmission rates required for real-time monitoring
  • Possible expansion to include additional sensor data such as temperature and humidity in order to optimize ventilation intervals with regard to heat losses during ventilation and thus reduce the consumption of heating energy
  • Provision of the infrastructure for all interested operators

Innovation Description

What Makes Your Project Innovative?

The innovation lies in the interaction of several properties and factors. The project uses various existing technologies and approaches to develop solutions to problems of public facilities related to the Corona pandemic. These are:

  • Small, networked NDIR sensors
  • LoRaWAN wireless technology for data transmission over several kilometers
  • Easy-to-understand visualization of the measured data
  • Open data and open licenses for public use of the project results
  • In addition, the project was developed and implemented in the interaction between civil society, companies, science and public administration.

What is the current status of your innovation?

The COMO pilot project ends on September 30, 2022. During the project, we distributed around 45 sensors in Berlin institutions and integrated them into the local LoRaWAN network. Likewise, three outdoor gateways and five indoor gateways were installed to support data transmission. The sensor data show publicly on the COMo website, if the institutions have agreed. The evaluation of the data and results is not yet complete, but it is already clear that reliable operation of a network of sensors with LoRaWAN technology only makes sense if this infrastructure is expanded and operated professionally. The number of sensors installed in an institution must also be increased significantly in order to enable models to forecast ventilation intervals. All findings are published and given to the Berlin Senate as recommendations for expanding the IoT infrastructure. The Berlin Senate is funding the project and is currently working on expanding the Smart City infrastructure.

Innovation Development

Collaborations & Partnerships

The project is funded and co-developed by Berlin Senate Chancellery. They are developing the Smart City strategy in Berlin.
The Technologiestiftung Berlin is a non-profit NGO. It runs several digitization projects with substantial community participation from various sectors. KOING GmbH initiated the project and is contributing its technical expertise in LoRa technology.
Berlin University of Applied Sciences (HTW) is developing the models for ventilating the rooms and forecasting the air quality

Users, Stakeholders & Beneficiaries

The project supports several groups in society, as described above:

  • Operators of the respective publicly accessible premises such as cultural institutions, educational institutions, restaurants, etc.
  • Potential users of said premises
  • The project also provides information for the Berlin Senate on the expansion of Smart City infrastructures

Innovation Reflections

Results, Outcomes & Impacts

What results and effects have been observed from the innovation so far? For the first time, COMo allows non-technicians to control their air quality based on measured values. This is relevant to facilities with many visitors (e.g. clubs, cinemas...). But also, it is evident that the number of installed sensors for single participants is still too small for general statements and forecasts on the development of indoor air quality.

How were the results and impacts measured? The number of transmitting sensors and the connection quality is continuously monitored, the individual sensors are marked. The air quality data are collected and are therefore available for further scientific evaluation. The operators were also asked about their experiences with the sensors by the HTW using interview guidelines.

What outcomes and impact do you expect in the future? A significant increase in the number of participating institutions and installed sensors as well as an improvement in LoRaWAN coverage.

Challenges and Failures

Main challenges that arose in the project were:

  • Due to the tense work situation during the pandemic, the interested operators of the rooms were often not able to give dates for the sensor installation in a timely manner. Since LoRa technology currently does not allow plug and play, support is required for the installation and registration process. This has made it difficult to fully deploy existing sensors quickly.
  • The unexpected patchy coverage of the urban area with LoRa gateways has caused a high maintenance effort for the sensors, since poor coverage causes high power consumption of the batteries used.
  • Finally, delivery bottlenecks caused by the pandemic have led to sometimes very long delivery times for the necessary devices.
    Overall, these obstacles have led to delays in the project process. This could only be partially compensated for by additional work, so that an extension of the project period was applied for and approved.

Conditions for Success

For the implementation of the project, it was essential that an intensive exchange process was carried out between the participants (TSB, HTW, KOING GmbH and last but not least representatives of the Senate Chancellery) in order to achieve a common understanding of the project goals and the possible results. This common understanding was the prerequisite for funding the project from public funds. Another important prerequisite for reaching the possible participants for the project was the network of the TSB in civil society.


There are known approaches to monitoring indoor air quality in order to reduce the risk of infection for restaurant visitors (in Brussels, for instance). Schools have also already used corresponding CO2 sensors, but rarely with comprehensive networking and central control options. DIY sensor projects are also known. However, the sensors used in these decentralized projects are often only technically suitable to a limited extent to generate permanently valid values. Today, the sensors used in heating and air conditioning often are able to measure the CO2 concentration in order to exchange the room air accordingly. However, these systems are currently not operated under the aspect of infection protection, the data collected are not used or published to visualize the CO2 concentration. It is probably possible to read out this data via interfaces of existing air conditioning systems and publish it as in COMo, in order to document compliance with indoor air hygiene standards.

Lessons Learned

In general, the communication of the project idea between those potentially involved and the target group is pivotal for the success of such a project. The communication is greatly encouraged if there is a physical location as a meeting point for communication and experimentation for those involved - in our case the CityLAB Berlin. Unexpectedly, the participating operators had few concerns about the privacy of the transmitted sensor data. This was expected of us in advance and we had sought advice from a lawyer. In fact, questions arose about the energy consumption of the sensors and gateways, or whether the sensors color can be changed to match the wall. The example shows that a previous survey and involvement of potential participants, anchored in urban society, helps to avoid false expectations of the participants. Furthermore, due to currently very long delivery times of hardware, it makes sense to consider and test several alternative systems to avoid delays in the project.

Year: 2022
Level of Government: Regional/State government


  • Implementation - making the innovation happen
  • Evaluation - understanding whether the innovative initiative has delivered what was needed
  • Diffusing Lessons - using what was learnt to inform other projects and understanding how the innovation can be applied in other ways

Innovation provided by:


Date Published:

2 January 2023

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