ASHRAE Standard 62.1 has long provided the framework for ventilation design and acceptable indoor air quality in commercial buildings. One path within the standard, the Indoor Air Quality Procedure (IAQP), allows engineers to use air cleaning and contaminant control strategies as part of the ventilation design approach.
While ASHRAE Standard 62.1-2019 permitted reduced outdoor air through IAQP, the standard contained fewer defined requirements around contaminant selection, air-cleaning validation, and post-installation verification. In response, ASHRAE introduced Addendum aa to Standard 62.1-2019 in early 2022 and formally incorporated those changes into ASHRAE Standard 62.1-2022.
The result was a more structured IAQP framework intended to improve consistency, simplify implementation for engineers, and ensure that air-cleaning technologies used for outdoor air reduction are supported by measurable performance criteria rather than interpretation alone.
IAQP in ASHRAE Standard 62.1-2019
ASHRAE Standard 62.1-2019 allowed IAQP to be used as an alternative to the Ventilation Rate Procedure (VRP). Under IAQP, engineers could incorporate air cleaning into the ventilation design to help reduce outdoor air while maintaining acceptable indoor air quality.
The framework relied heavily on the design engineer to:
- Identify contaminants of concern
- Determine acceptable concentration limits
- Evaluate occupant satisfaction
- Perform mass balance calculations
While this flexibility allowed IAQP to be applied across many project types, it also created inconsistencies in how systems were designed and validated.
In the foreword to Addendum aa, ASHRAE specifically acknowledged this issue, stating:
“Weaknesses in current requirements exist in items 1, 3, and 4 above.”
ASHRAE further noted:
“No measurement of any resulting concentration is currently required, so the effectiveness of any design is not measured or verified.”
This language is significant because it demonstrates that ASHRAE itself recognized weaknesses in the earlier IAQP structure and sought to strengthen the standard.
The Role of Addendum aa
Addendum aa to ASHRAE Standard 62.1-2019 was approved in January 2022 and served as the transition point between the 2019 and 2022 approaches.
The addendum introduced several major changes intended to strengthen IAQP implementation, reduce ambiguity, and improve accountability when reduced outdoor air strategies are used.
Key additions included:
- A defined list of Design Compounds (DCs)
- PM2.5 requirements
- Mandatory objective and subjective verification testing
- Minimum occupant satisfaction thresholds
Many of these changes were later formally integrated into ASHRAE Standard 62.1-2022.
The updates also help reduce the opportunity for air-cleaning technologies to be presented without measurable performance validation or clearly defined contaminant targets.
Key Changes Introduced in ASHRAE Standard 62.1-2022
Standardized Design Compounds and Design Limits
One of the most significant changes introduced through Addendum aa and adopted into 62.1-2022 was the inclusion of Table 6-5.
Rather than relying solely on engineers to determine their own contaminants of concern and acceptable limits, the updated framework established a defined list of design compounds and PM2.5 thresholds tied to recognized authorities.
This change simplified the IAQP process for design engineers by providing a consistent framework for contaminant selection and design targets while also reducing risk associated with subjective interpretation.
Post-Installation Verification Testing
Another major change was the introduction of required verification testing.
Under the revised IAQP framework, completed buildings must undergo:
- Objective testing of design compounds and PM2.5
- Subjective occupant satisfaction evaluation
ASHRAE established requirements for testing methodologies, measurement conditions, instrument specifications, and occupant satisfaction thresholds.
This represented a substantial shift from the earlier framework, where verification measurements were not required for compliance.
By requiring measurable post-installation validation, the updated standard helps ensure that IAQP systems perform as intended after implementation rather than relying solely on theoretical calculations.
Standardized Air-Cleaning Performance Documentation
The updated 2022 framework also references standardized air-cleaning test methods, including ASHRAE Standard 145.2 for gas-phase air-cleaning devices and ASHRAE Standard 52.2 for particulate filtration.
This addition supports more consistent evaluation of air-cleaning performance data used in IAQP system design and helps reduce the potential for unsupported performance claims.
The intent was not to endorse specific technologies, but to improve consistency, transparency, and accountability when air-cleaning systems are used as part of a reduced outdoor air strategy.
Why Some Projects Still Reference 62.1-2019
A common source of confusion is that building codes are not adopted nationally all at once.
ASHRAE standards become enforceable only after they are adopted by:
- State legislature
- Local jurisdictions
- Code bodies
- Authorities having jurisdiction (AHJs)
As a result, many projects today may still reference ASHRAE Standard 62.1-2019 even though ASHRAE Standard 62.1-2022 is available.
An additional layer of complexity is that addenda are not always automatically adopted when a jurisdiction adopts a standard version.
That means a jurisdiction could:
- Adopt ASHRAE Standard 62.1-2019
- But not formally adopt Addendum aa
In those cases, projects may still operate under the earlier IAQP framework unless the engineer or owner voluntarily chooses to follow the updated guidance.
Why the Addendum Still Matters
Even in jurisdictions still operating under 62.1-2019, Addendum aa remains important because it documents ASHRAE’s own recognition that portions of the earlier IAQP framework required improvement.
Importantly, these changes were not intended to create unnecessary complexity for engineers. In many ways, the updated framework simplifies IAQP implementation by providing clearer contaminant targets, defined testing criteria, and measurable methods for validating performance after occupancy.
The result is a more consistent and defensible IAQP process for engineers, owners, and occupants alike.
A Shift Toward Measurable IAQ Performance
The evolution from ASHRAE Standard 62.1-2019 to 62.1-2022 reflects a broader industry shift toward measurable indoor air quality performance.
Rather than relying primarily on theoretical calculations or designer-selected contaminant assumptions, the updated framework places greater emphasis on:
- Defined contaminants
- Quantified exposure limits
- Verification testing
- Occupant response
- Documented air-cleaning performance
The strengthening of the standard also helps ensure that IAQP applications are supported by measurable and verifiable performance criteria, reducing the ability for air-cleaning technologies to be represented without sufficient validation.
Final Considerations
ASHRAE Standard 62.1-2019 established the foundation for IAQP-based ventilation design, but ASHRAE Standard 62.1-2022 introduced substantially more structure around how IAQP should be implemented and validated.
The addition of standardized design compounds, verification testing, and measurable performance criteria reflects ASHRAE’s effort to improve consistency, simplify implementation for engineers, and reduce ambiguity within IAQP applications.
Because adoption timelines vary by jurisdiction, engineers should always verify:
- Which version of ASHRAE 62.1 has been adopted
- Whether relevant addenda have also been adopted
- What additional requirements may exist at the state or local level
- That they are following the latest version to help provide the highest standard of care for building owners and occupants
As IAQ expectations continue to evolve, the industry trend is clearly moving toward greater transparency, measurable contaminant control performance, and verified IAQP system effectiveness when reduced outdoor air strategies are utilized.
