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Standards, Research & Technology

MTG.ACR Air Change Rate


MTG.ACR will coordinate TC/TG/TRG/SSPC technical activities to help evaluate the technical basis and adoption of airflow rate specifications in terms of Air Change Rate (ACR) or Air Changes per Hour (ACH) for spaces such as cleanrooms, laboratories, patient rooms, operating rooms, and other similar spaces. Responsibilities include the development of research projects, development and presentation of technical programs for all types of spaces which currently require ACR specifications, and a special publication detailing aspects of the ACR philosophy and practice. The work of this MTG will potentially impact design guidelines, ASHRAE Handbook, and related ASHRAE standards. This MTG intends to involve other national and international groups and organizations in these efforts.



Cleanrooms, laboratories, and healthcare spaces including patient rooms, airborne infection isolation rooms, operating rooms and other similar facilities are required to maintain anywhere between 4 to 300
Air Changes per Hour (ACH). Guidelines, codes, and standards for such specifications are traditionally based on judgment of experienced practitioners. Since the ACH specification involves “volume” of the space which tend to penalize spaces with high ceilings without explicit supporting scientific justification. With increased emphasis on energy efficiency and associated costs of HVAC operations it is important to evaluate the basis of such specifications. The underlying principles of contaminant dilution and removal are similar across most of the different applications. While keeping the safety of people and products as a primary goal, this group will conduct systematic investigations through rational analysis, literature reviews, and research to determine the appropriate basis for the specification of dilution airflow rates for these applications. Additionally, this group will attempt to find a common - basis for dilution airflow
specifications to different applications such as cleanrooms, laboratories, and healthcare facilities. Where scientific basis cannot be definitively identified, research activities will be proposed through the ASHRAE research process.

This group will bring together expertise from various ASHRAE groups (TC 9.02, TC9.06, TC9.10, TC9.11, SSPC 62.1, SSPC 170) and from other non-ASHRAE organizations (see below) to work in close collaboration to achieve the following objectives:

  • Systematically investigate relationships between specified airflow rates and associated safety of people and products.
  • Evaluate a correlation between the strength and location of contaminant sources and airflow rates to obtain the desired levels of contamination control.
  • Compile definitions and descriptions of different terminologies for air change effectiveness, dilution effectiveness, ventilation effectiveness, and contaminant removal effectiveness.
  • Develop an in-depth understanding of relationship between ACR and various (ventilation) effectiveness definitions. Evaluate the impact of HVAC configuration including airflow distribution, flow path of contaminants, and locations and type of supply and return devices on ventilation effectiveness.
  • Quantitatively correlate concentration of contaminants with various measures of ventilation. Determine which measures correlate best, and the modeling assumptions necessary to support use of a variable as a design criterion.
  • Investigate the basis for the current ACR specifications for various facilities including cleanrooms, laboratories, patient rooms, operating rooms, and other similar spaces. Compare US standards and guidelines for such specifications with those available in other countries.
  • Based on the above evaluations publish the evaluations of the existing ACH specifications in the current ASHRAE guidelines and standards.
  • Develop recommendations for appropriate units for the specification of dilution airflow rates.

Also note this group would not be limited to ventilation and infiltration studies as in the scope of TC4.3. Activities of this group would help in optimizing the use of ASHRAE resources including ASHRAE research funds by avoiding duplicate efforts among different TCs. Findings of the research and literature review will be disseminated through special publications, ASHRAE Handbooks, ASHRAE conferences and other special conferences on the subject. The outcome of these efforts will be communicated to ASHRAE standards committees, regulatory authorities, and other similar organizations to facilitate any modifications in their codes and standards.




Committee Position





Kishor Khankari





Roland Charneux

Vice Chair




Jim Coogan



TC-9.10, Laboratory Systems

Adam Bare

Gary Goodson





Henry Hays



TC-2.2, Plant and Animal Environment

Carol Donovan

Steve Nicholas



TC 4.3, Particulate Air Contaminants

Bob Burkhead

Steve Taylor



TC-4.3, Ventilation Requirements and Infiltration

Josephine Lau

Gaylon Richardson



TC-5.3, Room Air Distribution

Jose Palma

Erich Binder



TC-5.8, Industrial Ventilation


Michael Baucom



TC-9.2, Industrial Air Conditioning

Michael Connor

Roger Lautz



TC-9.6, Healthcare Facilities

Michael Meteyer

Philip Naughton



TC-9.11, Clean Spaces

Wei Sun

Abdel Darwich



SSPC 62.1, Ventilation for Acceptable Indoor Quality

Hamid Habibi

Michael Locke



SSPC 170, Ventilation for Healthcare Facilities

Kevin A Scarlett

Gordon Sharp



I2SL, International Institute for Sustainable Laboratories

Daniel Doyle

Dr. Kenneth Mead



NIOSH, The National Inst for Occupational

James Bennett

Tom Smith



AIHA, American Industrial Hygiene Association

Clifford Cooper


Current Projects/ Goals

  • Developing Research Project Work Statement
  • Requesting topic suggestions for Annual Meeting



  • RTAR Approved
  • Program for ASHRAE 2018 Winter Conference
    • Forum: Ventilation Effectiveness: What Is It? Moderated by K. Khankari
    • Seminar: Modeling and Testing: Do Air Change Rates Have Lab Safety Covered? with presentations by K. Khankari and T. Smith


Meeting Times

  • MTG.ACR meets before and after ASHRAE conferences






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