ASHRAE’s Standard 241: A Health & Wellness Game Changer for Building Owners

By Tony Abate

Few events had more impact on commercial building owners than the Coronavirus pandemic.

In 2020 as the COVID pandemic rapidly expanded into all parts of daily life, many building operators were left uninformed and unaware of what to do to help protect occupants from the spread of airborne illness. So, for many, the decision was to keep people out of the building entirely.

That is why ASHRAE (American Society of Heating, Refrigerating and Air Conditioning Engineers) saw the need for better guidance and with urging from the US White House developed a standard for controlling infectious aerosols, to help provide patho\gen free air to occupants. ASHRAE Standard 241 was published in June 2023 to address the guidance needed.

The development of Standard 241 is a multi-faceted approach to address all types of environments, commercial buildings, residential, retail, healthcare, institutional and many others. The standard touches on many aspects of enhancing indoor environments to reduce the spread of infectious aerosols including:

  • 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 airflow, 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 and operate 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 procedure for assessing existing or new HVAC systems to determine if they are working properly and attributing to the equivalent clean air delivered to spaces.

The minimum ventilation requirements are those published in Standards 62.1, 62.2 and 170. Also, a minimum filtration requirement is set for MERV A-11.

A centerpiece of this new standard is the establishment of a calculation called Equivalent Clean Air for Infection (ECAi). This calculation allows for compliance to the enhanced values referenced in the standard to be accomplished by not just increasing volumes of outside air, but also by using air cleaning to provide the delivery of equivalent clean air.

In Table 5.1 of the standard, ECAi rates are established for all types of indoor environments. These would require significant increases if using outside ventilation alone. For example, in 62.1 2022, an office environment is required to bring in 17 cfm per person of outside air. In the 241 Standard, the requirement is 30 cfm per person of ECAi. If relying on just outside air, HVAC capacity would have to be increased significantly along with operating costs to condition the additional outside air. As a result, air cleaning and air disinfection technologies are critical to comply with the standard while also keeping up with sustainability goals and the reduction of carbon and greenhouse gas emissions.

A strong air cleaning technology that can deliver this performance is bi-polar air ionization (BPI). While there are many forms of BPI the most studied and performance tested is Dielectric Barrier Discharge (DBD) BPI. Many may know this as tube BPI. This technology has tested proven capability to deactivate organisms like bacteria and viruses. DBD BPI will also cause particles to agglomerate, becoming bigger and heavier and better caught by less air restrictive filters. The best part of all is that this technology uses little power and doesn’t require costly mechanical re-design or replacement. It can retrofit into most existing air systems, residing on the air supply side.

AtmosAir technology is extremely beneficial to meeting the ECAi compliance requirements of Standard 241.

  • AtmosAir has laboratory-tested effectiveness against infectious aerosols, and complies with UL safety standards, UL 867, and UL 2998.
  • AtmosAir systems very little power than other alternatives and impose negligible restriction to airflow, thereby contributing to Standard 241 ECAi requirements in a cost-effective way.
  • AtmosAir systems are low maintenance, and only require attention every 2 years.
  • In addition to reduction of infectious aerosols, AtmosAir has been tested to reduce PM 0.3- micron particles and has achieved a 125 CADR (Clean Air Delivery Rate) as tested to ANSI/ AHAM AC-1, which is referenced in Standard 241. AtmosAir technology is also effective on VOCs (Volatile Organic Compounds) and has been used in many applications showing measured effectiveness.

Lastly, the ASHRAE committee who created Standard 241, SPC 241 was voted to become SSPC 241 and will now act as a continuous maintenance committee with ASHRAE to further refine and develop this standard.

As identified in 241, most buildings will need to take measures to comply with the enhanced values for the delivery of equivalent clean air required. This can be done by increasing outside air introduction or using air cleaning or a combination of both.

For most buildings, looking purely at increasing outside air to meet the values listed in 241 for IRMM, (Infection Risk Mitigation Mode) will require significant investment. AC equipment may need to be larger to accommodate needed outside air, ducting may need to be enlarged, operating costs will increase, and AC run time will increase. Also engineering costs will be incurred to design what would be needed. This would be incurred for use that may sporadic.

As 241 details, increased outside air is not the only path to compliance. Air cleaning or systems that remove and / or deactivate pathogens, can be utilized to contribute to the ECAi values needed for Standard 241 compliance. This path can be a very advantageous path, most air cleaning systems do not require mechanical system re-design and do not use significant energy. Also, air cleaning systems can enable the deliver of pathogen free air all the time, not just when IRMM is identified.

Ideally the air cleaning technology can both facilitate the capture of viral sized particles, deactivate the organisms on these particles and sanitize the air.

As Standard 241 gains traction in the engineering and code enforcement communities, design standards will change to require 241 compliances. Many buildings who have well maintained advanced air cleaning technologies in place will find compliance noneventful. Others will need to assess their current situation and see what enhancements they will need to make to company and weight the options and costs.

In all situations, Standard 241 will cause buildings of all types to adjust, make enhancements and result in healthier indoor spaces for all occupants.

For ASHRAE’s press release link on Standard 241 click here.

Tony Abate is Vice President and Chief Technology Officer at AtmosAir Solutions and indoor air purification and monitoring technology company in Fairfield, CT.