CO2 Sensor SCD4x (coming soon)
Breaking the Size Barrier in CO2 Sensing

Once again, Sensirion trailblazes innovation in environmental sensing to create healthier and more productive environments. Having a proven track record in CO2 sensing, Sensirion now breaks the size barrier in CO2 sensing with the SCD4x - the first miniaturized CO2 sensor series that fits in a space of just one cubic centimeter. This disruptive innovation is based on the photoacoustic sensing principle and combines minimal size with maximum performance to open up numerous new integration and application possibilities.
- Unmatched price-performance ratio
- Smallest form factor: < 10.1mm x 10.1mm x 6.5mm
- Measurement range: 0 ppm - 40’000 ppm
- Accuracy: ±(50 ppm + 5% MV)
- Supply voltage range: 2.4V - 5.5V
- Fully calibrated digital I2C output
- Low power mode
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SCD4x Features and Benefits
Features | Benefits |
---|---|
Smallest form factor | Highest freedom of design |
Integrated RH + T sensor | Lowest integration and product cost |
Reflow solderable (SMT) | Space and cost-effective assembly |
Highest performance | Compatibility with all major standards |
Superior mechanical robustness | Accurate readings right after assembly |
Applications
The increasing environmental awareness not only affects the way how people live, travel and eat, but also how buildings are designed. Modern houses strive to achieve a very high energy efficiency to save natural resources that are mainly used for heating. A consequence is the trend towards tighter buildings that are much better insulated than older homes. Even the opening of windows is not allowed or possible anymore. Tight buildings mean there is less air exchange through walls, roofs, windows, cracks etc. which eventually requires an active ventilation system to get in fresh air to provide a healthy indoor environment. In addition to that, there is various building standards and codes (e.g. WELL, LEED, ASHRAE) that focus on how an efficient ventilation system shall be designed.
Humans are the main source of contamination indoors (e.g. smell, temperature, humidity (which can lead to mold), CO2, particulate levels, toxic gases, etc.) which is why the need for fresh air depends on the amount of people being present in a room and their activities (e.g. cooking, sports, resting). Based on the corresponding indoor air quality, it is possible to trigger a demand-controlled ventilation, which on one side ensures a healthy and comfortable environment and on the other side enables an energy-efficient operation. Energy-efficient in that sense means that the amount of air which is taken into the house, and eventually has to be treated (e.g. cooled, heated, filtered), is reduced to a minimum.
Sensirion will launch a ground-breaking CO2 sensor whose size and price allows the integration into various devices inside residential homes without sacrificing any performance compared to traditional NDIR sensors. The graphic shows exemplary applications/devices that can be equipped with Sensirion's innovative CO2 sensor solution.

Air Handling Unit (AHU) with Heat Recovery Unit
Description: AHUs can be found in residential multi-party buildings and commercial buildings. AHUs are devices that condition (heating, cooling, filtering, sometime de-/humidifying) the air according to the needs of the residents.
Goal of integrating CO2 sensor: Maximize energy-efficiency and provide best comfort and well-being.
Benefits of SCD4x:
- Compliance with building standards: Highly accurate CO2 readings ensure compliance to building standards to receive widely-accepted certificates.
- Dust resistance: Cover membrane leads to dust resistance that makes cumbersome maintenance obsolete (install’n’forget).
- Additional RHT sensor: Incorporated humidity and temperature (RHT) sensor in the CO2 module provides valuable information that help to increase energy-efficiency, optimize the control system and lower the noise level.
- Smallest size and flow independence: Allows freedom of your design to place the sensor where you want.
- Resistant to mechanical stress: Same performance specifications as traditional NDIR sensors with the benefit of being less sensitive to mechanical stress that can cause a drift in NDIR sensors and eventually lead to higher energy consumption of the ventilation system.
- Advanced algorithms: ASC (automated self-calibration) and FRC (forced recalibration) calibration algorithms enable maintenance free usage over the whole lifetime of your product.
- Reflow solderability: This feature of the SCD40 cuts down manufacturing cost and through put time as it can be automatically mounted like a standard SMD component.
Attractive pricing: The very attractive pricing makes it possible for the first time to also equip lower cost units with a real demand-controlled ventilation to increase your customer’s energy efficiency.
Wall-Mount / Duct-Mount Devices
Description: Sensor nodes being used inside ducts or rooms (mainly flush mount devices) to control the ventilation based on occupancy.
Goal of integrating a CO2 sensor: Enables highest user comfort and energy-efficiency as well as increases the lifetime of the ventilation system because it is only in operation when it is really needed and therefore can even reduce the noise level.
Benefits of SCD4x:
- Additional RHT sensor: Incorporated humidity and temperature (RHT) sensor in the CO2 module provides valuable information that help to increase energy-efficiency and enhances the user experience.
- Smallest size and flow independence: Allows freedom of your design to develop slimmest and innovative devices.
- Compliance with building standards: Highly accurate CO2 readings ensure compliance to building standards to receive widely-accepted certificates.
- Advanced algorithms: ASC (automated self-calibration) and FRC (forced recalibration) calibration algorithms enable maintenance free usage over the whole lifetime of your product.
- Resistant to mechanical stress: Same performance specifications as traditional NDIR sensors with the benefit of being less sensitive to mechanical stress that can cause a drift in NDIR sensors and eventually lead to higher energy consumption of the ventilation system and a lower noise level.
- Reflow solderability: This feature of the SCD40 cuts down manufacturing cost and through put time as it can be automatically mounted like a standard SMD component. Furthermore, there is no additional height gap between PCB and sensor when compared to hand soldered competitor CO2 products which allow the design of slimmest devices.
- Dust resistance: Cover membrane leads to dust resistance that makes cumbersome maintenance obsolete (install’n’forget).
- Attractive pricing: The very attractive pricing makes it possible for the first time to increase your market share of units with a CO2 monitoring feature that provides a full picture of your customer’s indoor air quality.
Air Purifiers (AP)
Description: Devices that are used to clean the air from contaminants like odors and particulates.
Goal of integrating a CO2 sensor: Reach a whole new level of healthy well-being by monitoring and purifying the air from contamination.
Benefits of SCD4x:
- Attractive pricing: The very attractive pricing makes it possible for the first time to also equip lower cost units with a CO2 monitoring feature that provides a full picture of your customer’s indoor air quality.
- Enhanced user experience: Highly accurate CO2 readings enable you to display warnings of unhealthy air levels and generate push notifications to your customers when it’s necessary to ventilate
- Additional RHT sensor: Incorporated humidity and temperature (RHT) sensor in the CO2 module provides valuable information that help to increase energy-efficiency and enhances the user experience.
- Smallest size and flow independence: Allows freedom of your design to place the sensor where you want.
- Advanced algorithms: ASC (automated self-calibration) and FRC (forced recalibration) calibration algorithms enable maintenance free usage over the whole lifetime of your product.
- Reflow solderability: This feature of the SCD40 cuts down manufacturing cost and through put time as it can be automatically mounted like a standard SMD component. Furthermore, there is no additional height gap between PCB and sensor when compared to hand soldered competitor CO2 products which allow the design of slimmest devices.
- Resistant to mechanical stress: Same performance specifications as traditional NDIR sensors with the benefit of being less sensitive to mechanical stress that can cause a drift in NDIR sensors and eventually lead to customer claims.
- Dust resistance: Cover membrane leads to dust resistance that makes cumbersome maintenance obsolete (install’n’forget).
Air Conditioner (AC) with Air Exchange
Description: Air Conditioners with Air Exchange function use CO2 value to control fresh air supply.
Goal of integrating a CO2 sensor: Avoid unhealthy CO2 concentrations, e.g. improve sleep quality by avoiding high CO2 concentrations during night in the bedroom.
Benefits of SCD4x:
- Smallest size and flow independence: Allows freedom of your design to place the sensor where you want.
- Additional RHT sensor: Incorporated humidity and temperature (RHT) sensor in the CO2 module provides valuable information that help to increase energy-efficiency and optimize your control system.
- Compliance with building standards: Highly accurate CO2 readings ensure compliance to building standards to receive widely-accepted certificates.
- Advanced algorithms: ASC (automated self-calibration) and FRC (forced recalibration) calibration algorithms enable maintenance free usage over the whole lifetime of your product.
- Resistant to mechanical stress: Same performance specifications as traditional NDIR sensors with the benefit of being less sensitive to mechanical stress that can cause a drift in NDIR sensors and eventually lead to higher energy consumption of the ventilation system.
- Reflow solderability: This feature of the SCD40 cuts down manufacturing cost and through put time because it can be automatically mounted like a standard SMD component. Furthermore, there is no additional height gap between PCB and sensor when compared to hand soldered competitor CO2 products which allow the design of slimmest devices.
- Attractive pricing: The very attractive pricing makes it possible for the first time to also equip lower cost units with a real demand-controlled ventilation ability that leads to an optimized energy consumption of your customer.
- Dust resistance: Cover membrane leads to dust resistance that makes expensive maintenance obsolete (install’n’forget).
- Real DCV: The accurate CO2 concentration output of the sensor enables real demand-controlled ventilation to have the system running at the optimum in terms of energy consumption.
Thermostats
Description: For basic products monitoring indoor environment conditions, enabling humidity and temperature control by heating and cooling, and for advanced products even control of ventilation from indoor air quality (IAQ) measurement.
Goal of integrating a CO2 sensor: Enable best comfort and well-being for the user depending on personal preferences. Increase energy-efficiency when connected with the ventilation systems. Provide full picture of the indoor air quality parameters.
Benefits of SCD4x:
- Smallest size and flow independence: Allows freedom of your design to come up with the most compact eye-catching devices.
- Additional RHT sensor: Incorporated humidity and temperature (RHT) sensor in the CO2 module provides valuable information that help to increase energy-efficiency and enhances the user experience.
- Reflow solderability: This feature of the SCD40 cuts down manufacturing cost and through put time because it can be automatically mounted like a standard SMD component. Furthermore, there is no additional height gap between PCB and sensor when compared to hand soldered competitor CO2 products which allow the design of slimmest devices.
- Attractive pricing: The very attractive pricing makes it possible for the first time to also equip standard thermostats with a real demand-controlled ventilation ability that leads to an optimized energy consumption of your customer when using a connected thermostat or a full picture of your customer’s environment having a stand-alone thermostat.
- Compliance with building standards: Highly accurate CO2 readings ensure compliance to building standards to receive widely-accepted certificates.
- Advanced algorithms: ASC (automated self-calibration) and FRC (forced recalibration) calibration algorithms enable maintenance free usage over the whole lifetime of your product.
- Resistant to mechanical stress: Same performance specifications as traditional NDIR sensors with the benefit of being less sensitive to mechanical stress that can cause a drift in NDIR sensors and eventually to customer claims.
- Dust resistance: Cover membrane leads to dust resistance that makes expensive maintenance obsolete (install’n’forget)
- Real DCV: In a connected thermostat the accurate CO2 concentration output of the sensor enables real demand-controlled ventilation to have the system running at the optimum in terms of energy consumption.
Air Exchanger (AE)
Description: Air purifiers with air exchange function uses CO2 value to control fresh air supply.
Goal of integrating a CO2 sensor: Avoid unhealthy CO2 concentrations indoors by using controlled outside air ventilation over a HEPA filter.
Benefits of SCD4x:
- Smallest size and flow independence: Allows freedom of your design to come up with the most compact eye-catching devices.
- Additional RHT sensor: Incorporated humidity and temperature (RHT) sensor in the CO2 module provides valuable information that help to increase energy-efficiency and optimize your control system.
- Compliance with building standards: Highly accurate CO2 readings ensure compliance to building standards to receive widely-accepted certificates.
- Reflow solderability: This feature of the SCD40 cuts down manufacturing cost and through put time as it can be automatically mounted like a standard SMD component. Furthermore, there is no additional height gap between PCB and sensor when compared to hand soldered competitor CO2 products which allow the design of slim devices.
- Dust resistance: Cover membrane leads to dust resistance that makes expensive maintenance obsolete (install’n’forget).
- Attractive pricing: The very attractive pricing makes it possible for the first time to also equip standard thermostats with a real demand-controlled ventilation ability that leads to an optimized energy consumption of your customer.
- Advanced algorithms: ASC (automated self-calibration) and FRC (forced recalibration) calibration algorithms enable maintenance free usage over the whole lifetime of your product.
- Resistant to mechanical stress: Same performance specifications as traditional NDIR sensors with the benefit of being less sensitive to mechanical stress that can cause a drift in NDIR sensors and eventually lead to higher energy consumption of your system.
- Real DCV: In a connected thermostat the accurate CO2 concentration output of the sensor enables real demand-controlled ventilation to have the system running at the optimum in terms of energy consumption.
Air Quality Monitor (AQM)
Description: Indoor air quality sensor node which monitors, visualizes and communicates air quality data.
Goal of integrating a CO2 sensor: Create awareness of air quality, capture bad air events and trigger counter measures to improve well-being.
Benefits of SCD4x:
- Smallest size and flow independence: Allows freedom of your design to come up with the most compact eye-catching devices.
- Additional RHT sensor: Incorporated humidity and temperature (RHT) sensor in the CO2 module provides valuable information that help to increase energy-efficiency and enhance your customer’s user experience.
- Reflow solderability: This feature of the SCD40 cuts down manufacturing cost and through put time as it can be automatically mounted like a standard SMD component. Furthermore, there is no additional height gap between PCB and sensor when compared to hand soldered competitor CO2 products which allow the design of slimmest devices.
- Dust resistance: Cover membrane leads to dust resistance that makes cumbersome maintenance obsolete (install’n’forget).
- Attractive pricing: The very attractive pricing makes it possible for the first time to also equip standard air quality monitors with a CO2 concentration monitoring ability that finally provides a full picture of your customer’s environment.
- Advanced algorithms: ASC (automated self-calibration) and FRC (forced recalibration) calibration algorithms enable maintenance free usage over the whole lifetime of your product.
- Resistant to mechanical stress: Same performance specifications as traditional NDIR sensors with the benefit of being less sensitive to mechanical stress that can cause a drift in NDIR sensors and eventually lead to customer claims.
- Compliance with building standards: Highly accurate CO2 readings help to ensure compliance to building standards to receive widely-accepted certificates.
PASens® Technology
PASens® Technology is based on the photoacoustic sensing principle. The photoacoustic sensing principle allows extreme miniaturization of the CO2 sensor without compromising sensor performance due to the fact that the sensor sensitivity is independent of the optical cavity size. The reduced size and the smaller number of integrated components result in a highly price-efficient BOM structure. Thanks to the miniaturizing and the economical BOM structure of these new CO2 sensor, the SCD4x will open up numerous possibilities for a whole new set of products and applications.
Click here to learn more about the measurement principle and key features of PASens® Technology.

Typical NDIR CO2 Sensor vs. SCD4x
Features | Typical NDIR CO2 Sensor | SCD4x CO2, RH + T Sensor | ||
---|---|---|---|---|
High selectivity | ![]() | ![]() | ||
Small size | ![]() | ![]() | ||
Additional sensor Outputs | ![]() | ![]() | ||
Cost-effective Assembly | ![]() | ![]() | ||
Mechanical robustness | ![]() | ![]() | ||
Cost-effective BOM | ![]() | ![]() |