Infineon’s XENSIV™ PAS CO2 sensor - Smallest sensor to meet California Title 24 Regulations - KBA234957

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Community Translation: インフィニオンのXENSIV™PASCO2センサ　- California Title 24 Regulationに適合する最小のセンサ-KBA234957

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The California Energy Code (Title 24, Part 6) has stringent performance requirements for DCV, which emphasizes both HVAC energy savings and indoor air quality. Infineon’s XENSIV™ PAS CO2 is the only gas sensor on the market today that meets all of California’s Title 24 mandatory building code requirements. Based on Photoacoustic Spectroscopy (PAS) technology, the PAS CO2 sensor guarantees high performance (±30 ppm ±3 percent of reading) in an exceptionally small form factor (14 mm x 13.8 mm x 7.5 mm).

Title 24 Regulation

California Code of Regulations Title 24, also referred to as California Building Standards Code (CBSC), is a collection of standards that help new, existing and remodeled properties (residential and public) safeguard the health and welfare of its occupants. Title 24 consists of 12 parts related to administrative, building, fire, residential, electrical, plumbing, mechanical, historical, green, existing codes, and referenced standard codes as well as energy codes. Part 6, also known as the California Energy Code, covers the requirements for Ventilation and Indoor Air Quality in section 120.1. More specifically, Part 6 refers to the energy efficiency standards for residential and nonresidential buildings as well as additions, alterations, and new construction. Under this provision, CO₂ sensors must be installed in each room to meet set criteria of no less than 1 sensor per 10,000 square ft floor space.

Provisions for CO₂-based Demand Controlled Ventilation (DCV) have been part of California’s building code (Title 24) since 1996 and became mandatory (for certain high-density applications) in 2005. In 2016, the Building Energy Efficiency Standards (BEES) outlined the need for air quality monitoring in areas that host an occupancy density greater than or equal to 25 people per 1,000 sqft. The demand for controlled ventilation in these areas calls for a CO₂ concentration of 600ppm or less.

Under Title 24 DCV, suitable CO₂ sensors must meet the following requirements:

• Be certified by the manufacturer to meet an accuracy of ±75 ppm or less at 600 ppm and 1,000 ppm (e.g., maximum allowable CO₂ density for classrooms) concentration when measured at sea level and an ambient temperature of 25°C.
• Be factory-calibrated and certified by the manufacturer to require calibration no more than once every 5 years.
• CO₂ levels outside the specified levels require the system to be able to provide a signal, which resets the air quality to a healthy level as required by Title 24 specifications; in other words, the monitoring sensor must be able to provide a signal that activates a ventilation system, which in turn provides the needed air exchange to achieve 600 ppm or better CO₂ level in the monitored space.
• CO₂ sensors must be able to cover up to 10,000 sqft floor space with a minimum of one sensor for this space and with an installation height of 3 ft to 6 ft above occupant head levels.

Infineon’s  XENSIV™ PAS CO2

With the stringent requirements of Title 24 in mind, Infineon conducted an in-depth analysis of their XENSIV™ PAS CO2 sensor specifications to determine whether the sensor meets all of the Title 24 requirements for California. Table 1 showcases critical findings related to the air quality accuracy for rooms/spaces of 1,000 sqft to 10,000 sqft.

Table 1:  Title 24 expectations for air quality accuracy

Title 24 requirements	XENSIV™ PAS CO2 Spec (@ 1 meas/200 s)		Competitor
	Zero Hour	5 years	Zero Hour	5 years
600 ppm ±75 ppm	±48 ppm	±57 ppm (meets Title 24)	±70 ppm	±118 ppm (does not meet Title 24)
1000 ppm ±75 ppm	±60 ppm	±75 ppm (meets Title 24)	±90 ppm	±170 ppm (does not meet Title 24)

Compared to other manufacturers on the market who claim Title 24 compliance, Infineon’s XENSIV™ PAS CO2 actually does meet the criteria. The PAS CO2 gas sensor offers the best specifications available, easy-to-use handling (e.g., assembly process), and crucial CO₂ accuracy of ±75 ppm with no need for manual calibration for 5 years.

General scenario

Studies on the accuracy of deployed CO₂ sensors used for DCV in California indicate that a substantial fraction of CO₂ sensors has errors greater than what is specified in Title 24. 47 percent of sensors had errors greater than 75 ppm at a concentration of 760 ppm, and 40 percent of sensors had errors greater than 75 ppm at a concentration of 1,010 ppm^[1]. A significant fraction of sensors have much larger errors (e.g., larger than 300 ppm). These concentrations of 760 ppm and 1,010 ppm are typical of the setpoint concentrations at which DCV systems increase outdoor air ventilation rates. Although the information from the aforementioned studies is 10 years old, based on these studies, many existing CO₂ sensors still do not meet current accuracy requirements for effective DCV implementations.

For further details, see:
https://www.infineon.com/dgdl/Infineon-PAS_CO2_sensor_Whitepaper-Whitepaper-v01_00-EN.pdf?fileId=8ac...

References

1. Fisk, William J, Sullivan, Douglas P, Faulkner, David, and Eliseeva, Ekaterina. 2010. "CO2 MONITORING FOR DEMAND CONTROLLED VENTILATION IN COMMERCIAL BUILDINGS". United States. https://doi.org/10.2172/983161. https://www.osti.gov/servlets/purl/983161.