Brief on ASHRAE’s Standard 241

In late 2022, the White House contacted ASHRAE to help prepare for the upcoming expiration of Title 42 (in May 2023) and the end of the COVID public health emergency. The government tasked ASHRAE with the job of creating guidance on how to operate buildings in a way to help prevent the spread of airborne infectious illnesses. 

During the pandemic, operators of indoor spaces were completely unprepared on how to mitigate and combat the spread of COVID. Proper guidance on how to make indoor spaces safe from the spread of the virus was inconsistent, and many people used untested technologies and inadequate products which were deemed to be ineffective. As a result, a new standard on how to protect people from the spread of infectious airborne illnesses in indoor spaces was needed and ASHRAE became the guiding force behind this initiative. 

By December 2022, ASHRAE assembled a SPC (Special Project Committee) under the leadership of William Bahnfleth, a former ASHRAE president, to serve as the leadership behind establishing the framework for the standard. By invitation only, a committee of industry experts and thought leaders, including Tony Abate, the CTO of AtmosAir, came together to work on outlining the standard. 

The committee started working on developing the framework of a standard in February 2023 and finished producing this standard in record-breaking time with its publication in June 2023. 

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 as 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 5 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. 

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. 

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