ASHRAE Guideline 42 2023

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ASHRAE Guideline 42-2023 — Enhanced Indoor Air Quality in Commercial and Institutional Buildings

Published By	Publication Date	Number of Pages
ASHRAE	2023

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ASHRAE Guideline 42 supplements ANSI/ASHRAE Standard 62.1, Ventilation and Acceptable Indoor Air Quality, by providing a global audience of engineers, designers, hygienists, air quality practitioners, and building owners a roadmap of varied, evidence-based best practices for improving ventilation and acceptable IAQ, beyond minimum requirements. The guideline steps users through concepts, research, and processes that have proven useful when effectively designed, installed, and operated. Guideline 42 also aims to supplement related publications from ASHRAE and other organizations. The sections of Guideline 42 are organized to reflect the path of air, beginning outside the building and moving through the building envelope, systems, and equipment to the indoor space.

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PDF Pages	PDF Title
1	ASHRAE Guideline 42-2023
3	Contents
4	Foreword 1. Purpose 1.1 The purpose of this guideline is to recommend measures that exceed minimum requirements for improving indoor air quality (IAQ) in commercial and institutional buildings. These measures are intended to provide enhanced IAQ that is acceptable to hu… 2. Scope 2.1 This guideline applies to spaces intended for human occupancy within commercial and institutional buildings except those within dwelling units in residential occupancies in which occupants are nontransient. 2.2 This guideline provides recommendations related to certain sources and for ventilation and air-cleaning system design, installation, commissioning, and operation and maintenance. 3. Definitions
7	4. Outdoor Air Quality 4.1 Regional Air Quality. ANSI/ASHRAE Standard 62.18 requires that the status of compliance with NAAQS5 be determined for the building site. If the area is not in compliance (nonattainment) for PM10, PM2.5, or ozone, the standard includes requirement…
8	4.2 Local Air Quality. A local air quality analysis that includes all known sources and variations in pollutants can help the designer and owner develop appropriate strategies to manage and enhance IAQ. A local air quality survey is intended to ident…
9	4.3 Documentation. Designers need adequate documentation of the local and regional air quality to inform their design decisions. Where provided to the building owner, such documentation helps inform decisions related to building and ventilation syste… 5. Buildings 5.1 Building Envelope and Interior Surfaces. The requirements for the building envelope in ANSI/ ASHRAE Standard 62.18 are intended to reduce the likelihood of moisture and air from damaging building materials. These requirements are also important f…
10	5.2 Buildings with Attached Parking Garages. Attached parking garages contain operational internal combustion engines—a well-established source for pollutants. It is preferred that parking garages be detached structures. If they are attached to the…
11	5.3 Requirements for Buildings Containing Environmental Tobacco Smoke (ETS) Areas and ETS- Free Areas. ASHRAE’s position is that all smoking activity inside and near buildings should be eliminated, as the medical community and its cognizant authori… 6. Systems and Equipment 6.1 Outdoor Air Intakes. The location and design of outdoor air intakes is critical for ensuring high-quality ventilation air. Careful selection of intake locations can reduce the entrainment of exhaust and other contaminants into the building. Louve…
12	6.2 Airstream Surfaces. According to ANSI/ASHRAE Standard 62.1, surfaces that are used to convey air must be resistant to microbial growth in accordance with a standardized test method, such as UL Standard 18137 or ASTM Standard C1338.38 A general ex…
13	6.3 Finned-Tube Coils and Heat Exchangers. Depending upon coil geometry and depth, some coils are easier to clean and maintain. Stainless steel coil casings in wet environments can help to enhance IAQ and longevity of equipment.
14	6.4 Drain Pans. Insulation beneath the bottom of the drain pan reduces condensation underneath the drain pan. Condensate traps must be designed to allow drainage while maintaining a seal between air above the drain pan and the air at the drain outlet…
16	6.5 Dehumidification Systems 6.6 Humidifiers and Water-Spray Systems. A humidifier or other water-spray system (such as direct evaporative cooler) operates optimally with an unobstructed downstream absorption distance to prevent condensation. The area immediately downstream may … 6.7 Ventilation System Controls. While airflow measurement stations are fairly common factory-installed accessories for larger, multiple-zone variable-air-volume (VAV) units, they are less common for single-zone packaged units. However, there are opt…
17	6.8 Access for Inspection, Cleaning, and Maintenance. This section discusses the provision of clearance and access to allow for inspection, cleaning, and maintenance of equipment. As ease of access can encourage regular maintenance, different access … 6.9 Selection of Equipment and Systems. Conditioning and moving ventilation air comprises a large fraction of building energy use. Design strategies to reduce energy and promote better IAQ include dedicated outdoor air systems (DOAS), energy recovery…
19	7. Indoor Air Quality 7.1 Ventilation Air Distribution. For enhanced IAQ, there are opportunities to improve upon the minimum requirements for how ventilation air is distributed to occupied zones and how it is mixed with room air. Systems with operating modes that have zo… 7.2 Air Classification and Recirculation. Air is classified according to the expected contaminants of a space, and ANSI/ASHRAE Standard 62.18 places limits on recirculating air between spaces with different air classifications.
21	7.3 Pollutants. Pollutants broadly include particles and gases and may include inert material, either organic or inorganic; reactive compounds; and living material such as viruses, bacteria, and fungi. This section focuses on the technical strategies…
23	7.4 Exhaust Duct Location. Separate exhaust ducts combined into a central duct can both improve dilution and increase the momentum of the exhaust plume. This is discussed in ASHRAE Handbook—HVAC Applications28, Chapter 45. This chapter also provide… 8. Procedures 8.1 General. ANSI/ASHRAE Standard 62.18 includes three procedures to design for indoor air quality (IAQ): Ventilation Rate Procedure (VRP), Indoor Air Quality Procedure (IAQP), and Natural Ventilation Procedure (NVP). These procedures offer three fun…
24	8.2 Ventilation Rate Procedure (VRP). The VRP is a prescriptive procedure in which outdoor air intake rates for various zone types (occupancy categories) are based on contaminant sources and source emission rates that are typical for the space type. …
28	8.3 Indoor Air Quality Procedure (IAQP). The IAQP is a performance-based procedure. Rather than prescribing rates based on occupancy categories, rates are calculated based on contaminant source emission rates for a list of design compounds and indoor…
31	8.4 Natural Ventilation Procedure (NVP). Natural ventilation generally does not involve filtration or conditioning of air that enters the building, so the designer must consider whether the outdoor air quality is naturally suitable for indoor environ… 9. Construction, System Start-Up, and Commissioning 9.1 Construction Phase
34	9.2 System Start-Up and Commissioning. It is important that the building and building systems be cleaned and operating properly prior to occupancy so these items do not contribute to poor IAQ. Consider the following: 10. Operations and Maintenance 10.1 Application. This section applies to buildings, their ventilation systems, and their components regardless of the version of ANSI/ASHRAE Standard 62.1 to which they were constructed or renovated. This section provides additional commissioning re… 10.2 Building Alterations or Change of Use. Building alterations or changes in space use without reevaluation and adjustment of the ventilation system can result in poor indoor air quality (IAQ). Common examples of changes include repurposing a priva…
35	10.3 Source Control during Operation. Environmental tobacco smoke (ETS), door mats, operational procedures, processes that occur in the building, occupant consumables, and durable goods are all contaminants that are brought in and can lead to poor IA…
36	10.4 Operations and Maintenance (O&M) Manuals. O&M manuals are critical tools for owners and operators. This topic is discussed in detail in Section 9 of this document. This section covers the activities of the O&M postwarranty phase. 10.5 Strategies to Improve Indoor Air Quality and Ventilation
37	10.6 Ventilation System Maintenance. Basic maintenance to meet minimum IAQ requirements is detailed in a variety of documents, such as ANSI/ASHRAE/ACCA Standard 180103; ANSI/ASHRAE Standard 62.18, Section 8; and ISO 55000.104 A comprehensive preventi…
42	10.7 Commissioning as Part of Operations. In addition to identifying potential energy savings, commissioning and maintenance programs can be used to evaluate systems to ensure IAQ goals are being met. 11. References
49	Informative Appendix A: Health Impacts of Air Pollutants A1. Particles
50	A1.1 Ultrafine Particles. Less is known about potential health effects due to exposure to particles smaller than 0.1 µm. One reason is that instruments that can reliably measure UFP concentration have not been available as long as instrumentation th… A2. Gases and Gaseous Mixtures A2.1 Oxidizing (Ozone). Ozone at ground level—not to be confused with the ozone layer in the upper atmosphere—is one of the major constituents of photochemical smog. It is formed by the reaction of sunlight (photochemical reaction) and pollutants… A2.2 Nitrogen Dioxide (NO2). As an air pollutant, NO2 has several correlated activities. At short-term concentrations exceeding 200 μg/m3, it is a toxic gas that causes significant inflammation of the airways. NO2 is the main source of nitrate aeros… A2.3 Sulfur Dioxide (SO2). Studies indicate that a proportion of people with asthma experience changes in pulmonary function and respiratory symptoms after periods of exposure to SO2.122 Exposure to SO2 concentrations of 500 μg/m3 should not exceed …
51	A2.4 Carbon Monoxide (CO). Carbon monoxide (CO) is a colorless, odorless gas that can be harmful, even fatal, when inhaled in large amounts. CO is released when something is burned. The greatest sources of CO in outdoor air are cars, trucks, and othe… A2.5 Organics—Volatile Organic Compounds (VOCs). In the built environment, organic gaseous pollutants that are volatile in the temperature range of occupied spaces are referred to as VOCs. The chemical backbones of VOCs are in the range of 6 to 16 … A3. Volatile Organic Compounds, Reactive Organic Gases, Smog, Content or Emissions A3.1 Terminology and VOC Limits. Regulations on the VOC content of some materials creates confusion between indoor air quality (IAQ) concerns and ambient smog concerns. In the latter third of the 20th century, photochemical smog in some urban areas w…
52	A3.2 Control Measures. Managing levels of indoor air pollutants relies on three factors: source control, dilution ventilation, and air cleaning. Where possible, source control is preferred, because the pollutant that is avoided is the easiest to cont… A3.3 Health Effects and Chemical Hygiene. The health effects of indoor VOCs remain incompletely characterized. For compounds with regulated or recommended occupational exposure limits, the indoor concentrations are generally below the occupational li…
54	Informative Appendix B: Humidity and Indoor Air Quality B1. Humidity Limit for Mechanically Cooled Spaces B2. Dehumidification Sensors and Controls B3. Naturally Ventilated Spaces Humidity and Indoor Air Quality
55	B4. Humidification B5. Microbials and Dampness
57	Informative Appendix C: Carryover in Energy Recovery Units C1. Energy Recovery Systems C2. Testing Energy Recovery Ventilation AHRI Standard 1060
60	Informative Appendix D: Case Studies D1. Source Control D2. Indoor Air Quality Procedure (IAQP) D2.1 Existing High-Rise Office Building in New York City
62	D2.2 New Construction: Training Center in Boston, MA
64	Informative Appendix E: Informative References and Bibliography

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Standard Title	ASHRAE Guideline 42-2023 — Enhanced Indoor Air Quality in Commercial and Institutional Buildings
Published Code	ASHRAE
Publication Date	2023

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