Christian Meyer
Senior Manager, Applications
Published: April 4, 2023

Many indoor parameters are well-known to people around the world, e.g., we know that 15 °C (60 °F) is cold and 35 °C (95 °F) is hot or 20% RH is dry and 80% RH is humid. We have a general feeling for temperature and humidity. But most of us do not have a feeling when it comes to gas (total volatile organic compounds, TVOCs) concentrations, which are of relevance, especially for cognitive scores and health.

Although a lot of research effort was spent, and hundreds of papers and articles were published in the last several decades, there is no universal, globally accepted standard for indoor air quality (IAQ) available. A standard, as defined here, is a requirement, which must be fulfilled by a legislative or subordinate authority for a country. Thus, depending on the publisher it may be called a study, guideline or standard. However, currently, these standards are not laws and IAQ is not a mandatorily required measurement for private homes or public buildings. Also, some of the governmental publications refer to one specific country and while other initiatives are internationally promoted with best-knowledge self-created parameters to define IAQ levels.

To make the standards around IAQ even more challenging, the limits for each standard differ. The upper TVOC limit that WELL allows is still considered “Medium Air” for UBA. Other sensor standards such as RESET, BREEAM and LEED often consider TVOC concentrations between UBA and WELL and have their own focus for green building certification.

Since TVOCs can be harmful to our health, we are still seeing commercial adoption, even with all the different standards in the marketplace, of defined gas concentrations and systems that take into consideration the strict WELL parameters, and adjust HVAC systems to ensure that we are always in a healthy air environment whether we are aware of the adjustments or not. To cover all standard eventualities, and speed market adoption, Renesas has adopted the most common and strict standards for IAQ:


Indoor Air Quality Standards and TVOC Levels


Renesas' UBA algorithm (IAQ 2nd Gen) focuses on health aspects and covers a large TVOC range as typically seen in homes (0.16ppm to 10ppm). The UBA study became very well-known and is a collection of 48 other research papers and reports that seeks to understand and summarize the best knowledge on indoor air quality. In particular, the TVOC references for indoor air quality are useful because not only does it identify l potential hazard levels, it also provides guidance on which actions are recommended based on these TVOC levels. Since UBA focus is homes, this operation mode allows higher TVOC concentrations during normal home events such as cooking, or poor building ventilation.

The upcoming Renesas public building air quality (PBAQ) release focuses on much smaller TVOC levels, which typically occur in offices with good ventilation systems (0.0005ppm to 1ppm). The PBAQ air quality definition supports a number of standards and focuses on the health and well-being of building occupants, focusing on the elimination of unsatisfactory air quality conditions (high TVOC and high CO2 levels, etc.) that would compromise occupants’ brain functions. Here, cognitive scores of personnel are of interest and smaller changes in TVOC need to be detected. A typical solution of this system can be seen in our HVAC Environmental Monitor for PBAQ Air Quality Definition Winning Combination.

For more information on this and other winning combinations visit the winning combinations page,, to see more solutions that can be used to help accelerate your designs to get to market faster.

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