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eLibrary >
ASHRAE Standard 62.1-2025 -- Ventilation and Acceptable Indoor Air Quality (ANSI Approved) >
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ASHRAE Standard 62.1-2025 -- Ventilation and Acceptable Indoor Air Quality (ANSI Approved), 2025
- ASHRAE Online Bookstore
- 62.1 Calculators
- Addenda
- Errata
- Return to Previous Page
- ANSI/ASHRAE Standard 62.1-2025 [Go to Page]
- Contents
- Foreword
- 1. Purpose [Go to Page]
- 1.1 The purpose of this standard is to specify minimum ventilation rates and other measures intended to provide indoor air quality (IAQ) that is acceptable to human occupants and that minimizes adverse health effects.
- 1.2 This standard is intended for regulatory application to new buildings, additions to existing buildings, and those changes to existing buildings that are identified in the body of the standard.
- 1.3 This standard is intended to be used to guide the improvement of IAQ in existing buildings.
- 2. Scope [Go to Page]
- 2.1 This standard applies to spaces intended for human occupancy within buildings except those within dwelling units in residential occupancies in which occupants are nontransient.
- 2.2 This standard defines requirements for ventilation and air-cleaning system design, installation, commissioning, and operations and maintenance.
- 2.3 In addition to ventilation, this standard contains requirements related to certain contaminants and contaminant sources, including outdoor air, construction processes, moisture, and biological growth.
- 2.4 This standard does not prescribe specific ventilation rate requirements for the following:
- 3. Definitions [Go to Page]
- 3.1 Terminology (See Figure 3-1)
- 3.2 Initialisms, Abbreviations, and Acronyms
- 4. Outdoor Air Quality [Go to Page]
- 4.1 Regional Air Quality. The status of compliance with ambient air quality standards shall be determined for the geographic area of the building site.
- 4.2 Local Air Quality. An observational survey of the building site and its immediate surroundings shall be conducted during hours the building is expected to be normally occupied to identify local contaminants from surrounding facilities that will b...
- 4.3 Documentation. Documentation of the outdoor air quality investigation shall be reviewed with building owners or their representative and shall include the following as a minimum:
- 5. Systems and Equipment [Go to Page]
- 5.1 Building Envelope and Interior Surfaces. The building envelope and interior surfaces within the building envelope shall be designed in accordance with the following subsections.
- 5.2 Buildings with Attached Parking Garages. In order to limit the entry of vehicular exhaust into occupiable spaces, buildings with attached parking garages shall be designed to
- 5.3 Requirements for Buildings Containing Environmental Tobacco Smoke (ETS) Areas and ETS- Free Areas. The requirements of this section must be met when a building contains both ETS areas and ETS-free areas. Such buildings shall be constructed and op...
- 5.4 Outdoor Air Intakes. Ventilation system outdoor air intakes shall be designed in accordance with the following subsections.
- 5.5 Particulate Matter Removal. Particulate matter filters or air cleaners having either
- 5.6 Finned-Tube Coils and Heat Exchangers
- 5.7 Drain Pans. Drain pans, including their outlets and seals, shall be designed and constructed in accordance with this section.
- 5.8 Humidifiers and Water Spray Systems. Steam and direct-evaporative humidifiers, air washers, direct- evaporative coolers, and other water spray systems shall be designed in accordance with this section.
- 5.9 Ozone-Generating Devices. The use of ozone-generating devices shall comply with Sections 5.9.1 and 5.9.2.
- 5.10 Ventilation Air Distribution. Ventilating systems shall be designed in accordance with the requirements of Sections 5.10.1 through 5.10.3.
- 5.11 Airstream Surfaces. All airstream surfaces in equipment and ducts in the HVAC system shall be designed and constructed in accordance with the requirements of Sections 5.11.1 and 5.11.2.
- 5.12 Mechanical and Indirect Evaporative Cooling Systems. Systems that cool by mechanical means or indirect evaporation shall be designed in accordance with Sections 5.12.1 and 5.12.2.
- 5.13 Direct Evaporatively Cooled Buildings. Systems that include cooling by direct evaporation into the supply air shall be designed in accordance with Sections 5.13.1 through 5.13.3.
- 5.14 Air Classification and Recirculation. Air shall be classified, and its recirculation shall be limited in accordance with Sections 5.14.1 through 5.14.4.
- 5.15 Exhaust Duct Location
- 5.16 Combustion Air. Fuel-burning appliances, both vented and unvented, shall be provided with air for combustion and removal of combustion products in accordance with manufacturer’s instructions. Products of combustion from vented appliances shall...
- 5.17 Local Capture of Contaminants. The discharge from noncombustion equipment that captures the contaminants generated by the equipment shall be ducted directly to the outdoors.
- 5.18 Building Exfiltration. Ventilation systems for a building equipped with or served by mechanical cooling equipment shall be designed such that the total building outdoor air intake equals or exceeds the total building exhaust under all load and d...
- 5.19 Ventilation System Controls. Mechanical ventilation systems shall include controls in accordance with Sections 5.19.1 and 5.19.2.
- 5.20 Ventilation System Emergency Control Modes. The building control system shall include modes of operation that adjust ventilation rates for emergency conditions. The control system shall allow initiation of the following modes:
- 5.21 Access for Inspection, Cleaning, and Maintenance
- 5.22 Legionella Risk. The building owner shall be provided with written documentation of the design information for all of the HVAC-related water systems and elements that are required to be addressed by ANSI/ASHRAE Standard 188.24
- 6. Procedures [Go to Page]
- 6.1 General. The Ventilation Rate Procedure (VRP), the Indoor Air Quality Procedure (IAQP), the Natural Ventilation Procedure, or a combination thereof shall be used to meet the requirements of this section. In addition, the requirements for outdoor ...
- 6.2 Ventilation Rate Procedure. The outdoor air intake flow (Vot) for a ventilation system shall be determined in accordance with Section 6.1.4 and Sections 6.2.1 through 6.2.6.
- 6.3 Indoor Air Quality Procedure (IAQP). Breathing zone outdoor airflow (Vbz) shall be determined in accordance with Sections 6.3.1 through 6.3.6.
- 6.4 Natural Ventilation Procedure. Natural ventilation systems shall comply with the requirements of either Section 6.4.1 or 6.4.2. Designers shall provide interior air barriers, insulation, or other means that separate naturally ventilated spaces fr...
- 6.5 Exhaust Ventilation. The Prescriptive Compliance Path in Section 6.5.1 or the Performance Compliance Path in Section 6.5.2 shall be used to meet the requirements of this section. Exhaust makeup air shall be permitted to be any combination of outd...
- 6.6 Design Documentation Procedures. Design criteria and assumptions shall be documented and made available for operation of the system after installation. See Sections 4.3, 5.10.3, 5.14.4, 6.2.6.1.4, 6.3.5, and 6.4.4 regarding assumptions to be deta...
- 7. Construction and System Start-Up [Go to Page]
- 7.1 Construction Phase
- 7.2 System Start-Up
- 7.3 Indoor Air Quality Procedure Verification
- 8. Operations and Maintenance [Go to Page]
- 8.1 General
- 8.2 Operations and Maintenance Manual. An O&M manual, either written or electronic, shall be developed and maintained on site or in a centrally accessible location for the working life of the applicable ventilation system equipment or components. Thi...
- 8.3 Ventilation System Operation. Mechanical and natural ventilation systems shall be operated in a manner consistent with the O&M manual. Systems shall be operated such that spaces are ventilated in accordance with Section 6 during periods of expect...
- 8.4 Ventilation System Maintenance. The building ventilation system components shall be maintained in accordance with the O&M manual.
- 8.5 Ventilation System Inspection, Verification, and Validation. The building ventilation system and components shall be inspected and verified to continue to meet requirements as designed in accordance with this standard. The inspection and verifica...
- 9. Normative References
- Normative Appendix A: Multiple-Zone System Ventilation Efficiency: Alternative Procedure [Go to Page]
- A1. System Ventilation Efficiency [Go to Page]
- A1.1 Average Outdoor Air Fraction. The average outdoor air fraction for the system (Xs) shall be determined in accordance with Equation A-1.
- A1.2 Zone Ventilation Efficiency. The zone ventilation efficiency (Evz) shall be determined in accordance with Sections A1.2.1 or A1.2.2.
- A1.3 System Ventilation Efficiency. The system ventilation efficiency shall equal the lowest zone ventilation efficiency among all ventilation zones served by the air handler in accordance with Equation A-9.
- A2. Design Process [Go to Page]
- A2.1 Selecting Zones for Calculation. Zone ventilation efficiency (Evz) shall be calculated for all ventilation zones.
- A3. Symbols
- Normative Appendix B: Separation of Exhaust Outlets and Outdoor Air Intakes [Go to Page]
- B1. General [Go to Page]
- B1.1 Application. Exhaust outlets and outdoor air intakes or other openings shall be separated in accordance with Section B2.
- B2. Determining Distance L [Go to Page]
- B2.1 General Equations. The minimum separation distance (L) shall be calculated using Equation B-1 through B-5b.
- B2.2 Special Cases. When a special case occurs, the alternate compliance conditions and equations in the following sections are permitted to be used to determine input values instead of those prescribed in Section B2.1.
- Normative Appendix C: Zone Air Distribution Effectiveness: Alternative Procedures [Go to Page]
- C1. Zone Air Distribution Effectiveness [Go to Page]
- C1.1 Personalized Ventilation Systems. For the purpose of calculating zone air distribution effectiveness for personalized ventilation systems, the breathing zone shall be 9 ft2 (0.8 m2) centered on each occupant with a height of 4.5 ft (1.4 m) from ...
- C2. Modeled Air Distribution System [Go to Page]
- C2.1 Computational Model. The computational fluid dynamics model for calculating zone air distribution effectiveness shall be in accordance with Sections C2.1.1 through C2.1.7.
- C2.2 Zone Air Distribution Effectiveness. Zone air distribution effectiveness (Ez) shall be computed in accordance with Equation C-1 for each computational cell in the breathing zone. The zone air distribution effectiveness of the system shall be the...
- Normative Appendix D: Air Density Correction Factor [Go to Page]
- D1. Air Density Correction Factor [Go to Page]
- D1.1 Design Condition. The air density correction factor (Eρ) shall be calculated at the design condition with the lowest coincident air density.
- D1.2 Elevation Adjustment. The elevation adjustment factor (CZ) shall be calculated in accordance with Equation D-1a (I-P) or D-1b (SI).
- D1.3 Temperature Adjustment. The temperature adjustment factor (CT) shall be calculated in accordance with Equation D-2a (I-P) or D-2b (SI).
- D1.4 Moisture Adjustment. The moisture adjustment factor shall be calculated in accordance with Equation D-3.
- D1.5 Air Density Correction. The air density correction factor (Eρ) shall be calculated in accordance with Equation D-4.
- D2. Alternative Calculation Methods [Go to Page]
- D2.1 Design Condition. The air density shall be calculated at the design condition with the lowest coincident air density.
- D2.2 Calculation Parameters. The calculation method shall include elevation above sea level, design air temperature, and design moisture content as factors contributing to the air density.
- D2.3 Air Density Correction. The air density correction factor (Eρ) shall be calculated in accordance with Equation D-5a (I-P) or D-5b (SI).
- Normative Appendix E: Ventilation Rates for Outpatient Facilities not Covered by ASHRAE/ASHE Standard 170 [Go to Page]
- E1. General
- E2. Ventilation Rates
- Informative Appendix F: Information on Selected National Standards and Guidelines for PM10, PM2.5, And Ozone
- Informative Appendix G: Acceptable Mass-Balance Equations for Use with the IAQ Procedure
- Informative Appendix H: Simplified Ventilation Rate Calculation for Multiple-Zone Recirculating Systems Serving Only Specified Occupancy Categories in Existing Buildings [Go to Page]
- H1. Use of this Appendix
- H2. Outdoor Air Intake
- H3. Zone Minimum Primary Airflow
- Informative Appendix I: Application [Go to Page]
- I1. Application [Go to Page]
- I1.1 New Buildings. All sections and normative appendices should apply to new buildings falling within the scope of this standard.
- I1.2 Existing Buildings. The standard should be applied to existing buildings at least in the circumstances described in the following subsections.
- Informative Appendix J: Documentation [Go to Page]
- J1. Outdoor Air Quality
- J2. Building Ventilation Design Criteria
- J3. Ventilation Rate Procedure
- J4. Indoor Air Quality Procedure
- Informative Appendix K: Rate Rationale
- Informative Appendix L: Information on Natural Ventilation [Go to Page]
- L1. Outdoor Air Quality Data [Go to Page]
- L1.1 Physically representative data accurately reflect the air quality conditions at the monitoring station from which they are derived. Data are considered physically representative if they are obtained from
- L1.2 Spatially representative data are collected from a monitoring site that may differ from the proposed project location but is informative of the air quality conditions at the proposed project location. Data may be considered spatially representat...
- L2. Natural Ventilation Rate
- L3. Prescriptive Path A Calculations [Go to Page]
- L3.1 Ventilation Intensity. Spaces have been defined by a ventilation intensity, which represents the amount of flow rate needed per Equation 6-1, divided by the floor area of the space. Its units are (L/s)/m2 of floor area or cfm/ft2 of floor area.
- L3.2 Single Openings. The flow through a single sharp opening due to bidirectional buoyancy-driven flow (Vbd_sharp) (see Etheridge and SandbergP16) is expressed as follows:
- L3.3 Vertically Spaced Openings. The flow rate (Vvs) through vertically spaced openings of areas As (the smallest sum of opening areas, either upper openings or lower openings) and Al (the largest sum of opening areas, either upper openings or lower ...
- L4. Control and Accessibility (Mixed-Mode Ventilation)
- Informative Appendix M: Compliance [Go to Page]
- M1. Section 4
- M2. Section 5
- M3. Section 6 Ventilation Rate Procedure [Go to Page]
- M3.1 Filtration
- M3.2 Ventilation Rates. Check compliance with the outdoor air intake flow (Vot) using the following process.
- M4. Section 6 Indoor Air Quality Procedure
- M5. Section 6 Natural Ventilation Procedure
- M6. Section 6 Exhaust
- M7. Ventilation for Existing Buildings [Go to Page]
- M7.1 Filtration. Filtration complies with Sections M7.1.1 and Section M7.1.2.
- M7.2 Outdoor Airflow. The following process may be used to determine if outdoor airflow rates comply with the VRP of the current standard. Occupied areas may be determined by measurement, dimensioned floor plans, or from the building manager’s data...
- M7.3 Controls. Confirm that ventilation system controls comply with requirements of Section 5.19, which requires that minimum ventilation airflows be maintained under all load conditions through manual or automatic controls.
- Informative Appendix N: Ventilation Rate Check Table
- Informative Appendix O: Indoor Air Quality Procedure
- Informative Appendix P: Informative References
- Informative Appendix Q: Addenda Description [Go to Page]
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