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Ensuring Safe Air: Insights from the Latest ASHRAE Standard 'Control of Infectious Aerosols'


The latest ASHRAE Standard 241-2023 under the theme 'Control of Infectious Aerosols' provides comprehensive guidelines to help decision-makers implement strategies to minimize the risk of infection. The guidelines include the option for use of a range of recommended air cleaning technologies for inactivating infectious aerosols.

Here’s a breakdown of key takeaways from the report that help deliver safer air in healthcare facilities.

Understanding Airborne Transmission and Engineering Controls

Airborne transmission of diseases occurs when an infectious dose of active pathogens is inhaled. Reducing the concentration of these pathogens through engineering controls – such as ventilation, filtration, and air disinfection – can significantly lower infection risks. While these measures are vital, they should be part of a broader risk management strategy.

A new Concept: Equivalent Clean Airflow Rate (ECAi)

The standard introduces the concept of Equivalent Clean Airflow Rate (ECAi), which can be achieved through one or a combination of:

  • Introducing outdoor air
  • filtered recirculated air or
  • air that has been disinfected by advanced technologies.


This flexibility allows for tailored solutions that meet specific needs, whether through mechanical or natural ventilation, or a mix of both.

Higher Standards Require More Rigorous Testing

ASHRAE has set new high standards for filtration and air cleaning technologies, surpassing current standards. These new requirements require that filters and air cleaners are tested rigorously for performance and safety, fostering trust in these technologies.


Download the scientific research report – Genano technology eliminates 99,999% of viruses and bacteria from indoor air.
Research done by impartial research centre VTT (Technical Research Centre of Finland)

Advanced Air Cleaning Systems for Pathogen Inactivation

The report emphasizes the effectiveness of in-duct and in-room air cleaning systems. Whether installed in air-handling units or within specific zones, these systems must have proof of their effectiveness to reduce infectious aerosols.


Air cleaning systems designed to inactivate infectious aerosols utilize technologies such as:

  • Ultraviolet (UV)
  • Electrostatic
  • Photocatalytic and
  • Ionizing air cleaning systems.

According to ASHRAE guidelines, technologies for pathogen inactivation can be used alone or in combination with mechanical fiber filters. Ensuring both effectiveness and safety, these technologies are essential for removing airborne pathogens from the air stream.

Mechanical fiber filters alone do not ensure pathogen inactivation, they simply remove the pathogens from the air, reducing airborne concentration. This can help to achieve the desired ECAi for a particular space.

More options

But ASHRAE 241 also recognizes the value of technologies that are designed to inactivate pathogens.

“ASHRAE 241 is a major step forward for organizations that follow ASHRAE guidelines. The standard is focused on achieving safe air through the use of any air cleaning technologies that are proven to be safe and effective and meet the ASHRAE performance test standards. Previously the range of prescribed options was narrower.

This means that technologies like Genano, which both filters and kills airborne pathogens, can play an important role in delivering safe air, whether that is in the air handling system or in room deployment.

Indeed, one of the ASHRAE-approved methods for measuring effectiveness of air cleaning technologies has shown that in room air decontamination can be very effective in achieving desired levels of ECAi”, states Genano’s Medical Export Director Petri Vaulo.

Why This Matters?

As professionals responsible for patient safety and air quality in medical facilities, these guidelines are crucial. ASHRAE reports are invaluable resources for professionals in the field, providing them with the latest research, standards, and best practices to enhance system efficiency and building performance.

Implementing these advanced standards ensures that you provide the safest and cleanest air possible, enhancing patient care and operational efficiency.

Download our free guide to learn more about good indoor air quality: