ASHRAE has published its pioneering consensus-based, code enforceable standard, developed to reduce the risk of infectious aerosol transmission in buildings.

ASHRAE Standard 241, Control of Infectious Aerosols can be purchased at

Standard 241 establishes minimum requirements to reduce the risk of airborne disease transmission, such as SARS-COV-2 virus, which causes COVID-19, the flu virus and other pathogens in buildings like single and multi-family homes, offices, schools and healthcare facilities. The standard applies to new and existing buildings and major renovations and provides requirements for many aspects of air system design, installation, operation and maintenance.

Important topics addressed in the standard:

  • Infection Risk Management Mode (IRMM) – Establishes requirements for an infection risk management mode (IRMM), which applies during identified periods of elevated disease transmission risk. Authorities having jurisdiction can determine when the enhanced protections of Standard 241 are required. Resilience (the ability to respond to extreme circumstances outside normal conditions) in indoor air quality control design and operations is introduced.
  • Requirements for Equivalent Clean Airflow Rate – Sets requirements for equivalent clean airflow rate target per occupant of pathogen free air flow, reducing the risk of infection.
  • Requirements for Use of Filtration and Air Cleaning Technology – Provides extensive requirements for use of filtration and air cleaning (such as HEPA filters, air ionizers, or UV lights) to achieve equivalent clean airflow requirements and be cost effective effectively and safely.
  • Planning and Commissioning – Provides assessment and planning requirements for being ready for the times when there is an event with increased disease causing pathogen transmissions. The standard has a building readiness plan, that documents procedures for assessing existing or new HVAC systems to determine if they are working properly and attributing to the equivalent clean air delivered to spaces.
For additional details or to purchase Standard 241