ASHRAE published the 2025 edition of Standard 62.1, Ventilation for Acceptable Indoor Air Quality, with the standard's most recent addenda dated September 30, 2025. This updates the baseline ventilation standard that most commercial buildings are designed and tested against, changing several calculations that a TAB technician runs during ventilation rate verification, including outdoor air intake and exhaust separation, air density correction, exhaust system performance, and demand-control ventilation sequencing.
ASHRAE 62.1 is the industry baseline for minimum ventilation rates and acceptable indoor air quality in commercial and institutional buildings. It gets referenced directly or indirectly by most state mechanical codes, and it is the standard most testing, adjusting, and balancing (TAB) reports use to state whether a system delivers the outdoor air quantities a design intended. The 2025 edition succeeds the 2022 edition and consolidates a set of addenda that ASHRAE finalized through September 30, 2025 (Addendum h, among others, on that date). According to the ANSI Blog, the new edition carries forward several structural and calculation changes rather than a simple renumbering.
For a building owner or facility team, the practical question is whether ventilation rate verification performed under the old edition still matches what a newer design, permit, or commissioning scope will expect. For a TAB provider, the practical question is which field calculations and report fields need to update before the next verification cycle.
Several changes affect field verification directly, rather than sitting purely in the design chapters:
The Whitescarver Engineering summary of the 2025 edition also points to expanded humidity control language and new emergency ventilation control requirements for atypical operating modes (occupied, occupied-standby, and unoccupied), which affects how a building automation system should be sequenced and, in turn, what a TAB verification confirms is happening at the diffuser or terminal unit.
Outdoor air intake placement relative to exhaust outlets, plumbing vents, and other contamination sources has always mattered for indoor air quality, but 62.1-2022 handled it largely through prescriptive minimum distances. The 2025 edition introduces calculation methods that account for factors such as discharge velocity and direction rather than a flat distance table alone. For a TAB technician verifying outdoor air quality intake conditions, this means a field report may need to document the specific inputs used to satisfy the calculation, not simply confirm a measured distance against a single number.
Ventilation rates in 62.1 are volumetric airflow requirements, and volumetric airflow measured in the field is sensitive to actual air density at the point of measurement, which shifts with elevation, temperature, and barometric conditions. The 2025 edition adds a formal air density correction factor that applies across ventilation zone calculations rather than leaving density assumptions implicit. For ventilation rate verification, this changes how a measured cfm value gets reconciled against a design intent value, particularly at higher elevations or on projects where design conditions and field test-day conditions diverge meaningfully. A TAB report that shows raw field readings against a 2022-edition target without applying the correct density basis may not reconcile the way a reviewer expects.
62.1 has historically allowed a performance path for evaluating exhaust systems as an alternative to prescriptive exhaust rate tables. The 2025 edition revises how that performance path is calculated. Because exhaust airflow verification and outdoor air intake verification are tied together in an overall building pressurization and ventilation balance, a change on the exhaust side changes what a technician needs to confirm on a building's net airflow condition, not only the exhaust registers themselves.
Demand-control ventilation modulates outdoor air based on measured occupancy indicators such as CO2, and 62.1-2025 introduces a new control sequence for how that modulation should occur. For functional testing and ventilation rate verification on a DCV-equipped system, the sequence of operations a technician checks against, and the range of conditions across which minimum ventilation must still be maintained, now has an updated reference point. Field verification of a DCV sequence written to the 2022 edition's assumptions should be checked against whether the project intends to follow the updated 2025 sequence, particularly for new construction and major renovation projects using the current code cycle.
62.1 allows certain reductions in outdoor air rates when air-cleaning systems remove specific contaminants, and the 2025 edition adds performance requirements for those systems, including a calculation for the system's efficiency at the end of its useful life for certain contaminants, rather than assuming initial (clean-filter) performance throughout the equipment's service life. For facilities relying on air-cleaning credits as part of their ventilation strategy, verification and documentation now need to address performance degradation over time, with direct implications for filter change intervals and ongoing IAQ testing.
| Category | ASHRAE 62.1-2022 | ASHRAE 62.1-2025 |
|---|---|---|
| Intake/exhaust separation | Prescriptive minimum distance table | New calculation method accounting for discharge conditions |
| Air density in zone calculations | Density assumptions largely implicit | Formal air density correction factor applied to ventilation zone math |
| Multiple governing standards | No single reconciliation method specified | New method for calculating system ventilation requirements across standards |
| Air-cleaning system credits | Based largely on rated/initial performance | Performance requirements including end-of-useful-life efficiency calculation |
| Exhaust performance path | Prior performance path methodology | Revised performance path calculation |
| Demand-control ventilation | Prior DCV control sequence | New DCV control sequence |
| Operations and maintenance (Section 8) | Table 8-1 duplicated Standard 180 maintenance tasks | Restructured inspection task table (Addendum h) split into verification and validation tasks with set frequencies |
ASHRAE released the 2025 edition of Standard 62.1 in 2025, consolidating addenda to the 2022 edition, with the most recent of those addenda approved on September 30, 2025. The 2025 edition succeeds ASHRAE 62.1-2022, which had been the reference edition since August 2022.
ASHRAE standards themselves are not automatically enforceable. Applicability depends on which edition your local mechanical or building code adopts by reference, and on what edition a specific project's design documents, permit, or commissioning specification cite. Existing buildings generally continue to operate against the edition that was in force when they were designed and permitted unless a renovation, code update, or owner requirement triggers a review against the newer edition.
Ventilation rate verification is the field process of measuring actual outdoor air and exhaust airflow at intakes, terminal units, and exhaust points, then comparing those measurements against the design's calculated requirements. Because 62.1-2025 changes some of the underlying calculations (air density correction, exhaust performance path, multi-standard reconciliation), the target values a technician verifies against can differ from what the 2022 edition would have produced for the same building, even when nothing about the physical system changed.
Not automatically. A system balanced and verified under 62.1-2022 remains validly documented against that edition. Re-testing under the 2025 edition typically becomes relevant when a renovation, tenant improvement, recommissioning cycle, or code adoption specifically calls for compliance with the current standard.
It changes how a measured volumetric airflow reading gets reconciled against a design target, since the correction factor accounts for actual air density at the point and conditions of measurement rather than a fixed assumption. A ventilation rate verification report prepared under the 2025 edition should show the density basis used for that reconciliation, particularly on projects at higher elevations or where test-day conditions differ meaningfully from design conditions.
ASHRAE publishes individual addenda as PDFs on its standards and guidelines page, including Addendum h, and the full 2025 edition is available for purchase through ASHRAE and ANSI-authorized distributors, including a product preview page that lists the standard's publication details and table of contents.
A new edition of the baseline ventilation standard is a reasonable moment to check whether your building's current ventilation rate verification documentation still lines up with what a design team, code official, or tenant improvement scope will expect next. Aero Performance Group's testing and balancing services cover the field measurement, calculation, and reporting work that ventilation rate verification requires, including the airflow and pressure readings that feed directly into 62.1 compliance documentation. If your last verification predates September 2025 and a renovation, recommissioning cycle, or permit review is coming up, it is worth confirming which edition your project needs to document against before the field work starts.