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ASHRAE Standard 241-2023 -- Control of Infectious Aerosols, 2023
- Online Supporting Files
- ASHRAE Online Bookstore
- ASHRAE Standard 241-2023 [Go to Page]
- Contents
- Foreword
- 1. Purpose [Go to Page]
- 1.1 The purpose of this standard is to establish minimum requirements for control of infectious aerosols to reduce risk of disease transmission in the occupiable space in new buildings, existing buildings, and major renovations to existing buildings,...
- 1.2 This standard defines the amount of equivalent clean airflow necessary to substantially reduce the risk of disease transmission during infection risk management mode.
- 2. Scope [Go to Page]
- 2.1 This standard
- 2.2 This standard does not determine the conditions under which infection risk management mode should be invoked.
- 2.3 No requirement in this standard shall be used to circumvent any health, safety or comfort regulations required by the authority having jurisdiction.
- 3. Definitions, Abbreviations, and Acronyms [Go to Page]
- 3.1 General. Certain terms, abbreviations, and acronyms are defined in this section of the standard. When the tense or number of the term differs from the defined terms, the defined term still applies. These definitions are applicable to all sections...
- 3.2 Definitions
- 3.3 Abbreviations and Acronyms
- 4. Compliance [Go to Page]
- 4.1 Prerequisites
- 4.2 Requirements
- 5. Equivalent Clean Airflow for Infection Risk Mitigation [Go to Page]
- 5.1 Minimum Equivalent Clean Airflow Rate
- 6. Air Distribution and Natural Ventilation [Go to Page]
- 6.1 Clean Airflow Rate. The clean airflow rate to each zone, as shown in Figure 6-1, shall be greater than or equal to the minimum equivalent clean airflow required, as expressed by Equation 6-1.
- 6.2 Zone Air Distribution Category. Each ventilation zone shall be assigned a zone air distribution category as described in Table 6-1.
- 6.3 Natural Ventilation. Natural Ventilation systems shall be designed in accordance with the methods described in ANSI/ASHRAE Standard 62.11, ANSI/ASHRAE/ASHE Standard 170 3, or an engineering analysis approved by the AHJ.
- 6.4 Mixed-Mode Ventilation. Mixed mode natural ventilation systems shall be evaluated independently under all operating conditions. The systems shall be designed in accordance with the natural ventilation and mechanical ventilation methods described ...
- 6.5 Air Cleaning Systems
- 7. Air Cleaning [Go to Page]
- 7.1 Testing Requirements. The effectiveness and safety of cleaning systems shall be determined by testing an air cleaning system or equivalent system in accordance with Section 7. A responsible party designated by the authority having jurisdiction (A...
- 7.2 Calculated Effectiveness of Air Cleaning Systems
- 7.3 Mechanical Fibrous Air Cleaning Systems. The effectiveness (delivered equivalent clean airflow rate) and safety of mechanical fibrous filters used inside HVAC systems, ductwork, or plenums, and in-room air cleaning systems that employ only mechan...
- 7.4 Air Cleaning Systems that Inactivate Infectious Aerosols. The effectiveness and safety of air cleaners with technologies that inactivate infectious aerosols shall be determined in accordance with Section 7.4. This applies to all air cleaning tech...
- 8. Assessment, Planning, and Implementation [Go to Page]
- 8.1 Building Readiness Plan (BRP). The BRP shall be created after the assessment, planning, and implementation phases to describe the engineering and nonengineering controls that the facility’s systems will use to achieve its target equivalent clea...
- 8.2 Existing Buildings Assessment, Planning, and Implementation
- 8.3 New Construction and Major Renovations. The requirements of this section apply to new buildings and systems and renovations to existing buildings and systems. Planning and implementation of engineering controls to achieve VECAi in new constructio...
- 9. Operations and Maintenance [Go to Page]
- 9.1 Operations
- 9.2 Maintenance
- 10. Dwelling Units—Additional Requirements [Go to Page]
- 10.1 General Requirements
- 10.2 Existing Buildings—Single Family and Multifamily Dwellings
- 10.3 Separation Area for Infected Occupants.When a household member is known to be infected, a separate fully enclosed space shall be used as a separation area. For the separation area, equivalent clean airflow supply shall meet or exceed required VE...
- 10.4 Dwelling Units with Vulnerable Occupants. Dwelling unit equivalent clean airflow supply shall meet or exceed required VECAi per Equation 5-1 using the health care patient room occupancy category listed in Table 5-1.
- 11. Normative References
- Normative Appendix A: Determining Air Cleaning System Effectiveness and Safety [Go to Page]
- A1. Testing Procedure [Go to Page]
- A1.1 Parity. Testing for effectiveness and safety shall be performed using identical operating conditions of the air cleaning system equipment, but the testing shall be performed separately. The environmental and airflow conditions in the test enviro...
- A1.2 General Testing Requirements. Performance tests of air cleaning systems, whether mounted inside an air-handling unit (AHU) ductwork or plenum or placed in the occupied zone, shall be performed in accordance with Section A1.2.
- A1.3 Effectiveness Testing Requirements. Effectiveness testing for all air cleaning systems covered by a consensus standard listed in Section A1 shall be performed following the methodology of that standard with the challenge microorganism specified ...
- A1.4 Safety Testing Requirements. Air cleaning systems shall be tested for safety under the requirements of Section A1.4.
- Normative Appendix B: Assessment, Planning, and Implementation [Go to Page]
- B1. Occupied Space Inventory
- B2. Equipment Inventory
- B3. Potential Respiratory Separation Area
- B4. Ventilation [Go to Page]
- B4.1 Minimum Outdoor Airflow Requirements. Mechanical ventilation in nonresidential spaces shall use either of the following procedures to determine compliance for the current space use and occupancy:
- B4.2 Coil Condition and Capacity. The coils shall be evaluated as follows:
- B4.3 Ventilation System Controls. Ventilation systems controls shall be evaluated to check the following:
- B4.4 Pressurization. Building and space pressurization shall be assessed, including
- B5. Controlling Sensors
- B6. Control Strategies and Sequences Of Operation
- B7. Outdoor Air Increase Verification
- B8. Health care [Go to Page]
- B8.1 Capture Test. Capture devices placed in rooms in spaces expected to be occupied by infected people shall be verified by a capture test and compared against the design assumption of capture effectiveness to prove that air cleaner performance comp...
- B8.2 Room Pressure Test. Room pressurizations used for containment shall be verified by one of the following methods:
- B9. Commissioning Functional Performance Tests (FPTs)
- B10. New Construction and Major Renovation [Go to Page]
- B10.1 Owners Project Requirements (OPR). The OPR shall include
- B10.2 Design Documentation. The following documentation is required to be created by the design team.
- Normative Appendix C: In-place Test Method for Determining the Equivalent Clean Airflow for Infection Risk Mitigation (ECAi) of a Single Occupied Space by Means of Tracer Aerosol Decay [Go to Page]
- C1. Equipment
- C2. Preparation
- C3. Test Execution
- C4. Analysis of Data [Go to Page]
- C4.1 Calculate the target volumetric airflow VECAi,ADn,T for all aerosol detectors ADn (n = 1 – 4+) using Equation C-1 and calculate the target air changes per hour (ACHT) using Equation C-2.
- C4.2 Calculate the global areas under the curve for target (AUCT) and actual (AUCA) as follows:
- C4.3 Calculate the actual volumetric airflow VECAi,ADn,En for each aerosol detector and each E1, E2, and E3 particle size range, using Equation C-9 33.
- C4.4 Calculate the actual weighted average, VECAi,ADn,avg,A for each particle size bin, E1, E2, and E3, and each aerosol detector using the weights WE1, WE2, and WE3 from Section 7.4.1 using Equation C-10.
- C4.5 Calculate the target and actual global averages, VECAi,avg,T and VECAi,avg,A, using the average of all the respective values of VECAi,ADn,T and VECAi,ADn,avg,A calculated for the space in Section C4.1 and Section C4.4 using Equation C-11 and Equ...
- C4.6 To determine the test outcome:
- C5. Reporting
- Informative Appendix D: Risk Assessment Model for Determination of Minimum Equivalent Clean Airflow Rates
- Informative Appendix E: Building Readiness Plan Template
- Informative Appendix F: Equivalent Clean Airflow Calculator
- Informative Appendix G: Practical Guidance for Epidemic Operation of Energy Recovery Ventilation Systems
- Informative Appendix H: Exhaust Re-entrainment Guide
- Informative Appendix I: Informative References and Bibliography [Go to Page]
- I1. References
- I2. Bibliography [Go to Page]
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