ASHRAE Standard 241

What is ASHRAE 241?  

In summary, the federal government recognized the enormous social and economic impact resulting from the COVID-19 lockdown.  They therefore sought to promote IAQ regulations for essential buildings in order to prevent another widespread lockdown in a future pandemic.  The White House commissioned ASHRAE (the American Society of Heating, Refrigerating and Air-Conditioning Engineers) to quickly develop a guide to reduce the likelihood of infection between building occupants during another pandemic event.  ASHRAE 241 was published in July, 2023 after only 4 months of development.

The standard essentially requires buildings, both commercial and residential, to deliver a much higher quantity of pathogen-free air to its occupants during a period of pandemic risk. What is the ultimate goal? To prevent occupants from inhaling an infectious dose of particles.  This can be accomplished through a variety of mechanisms - higher ventilation, particle filtration, disabling energy-saving modes, occupancy limits, and/or pathogen deactivation.  However, a key focus of the standard is enhanced air cleaning to achieve the high clean air delivery rates imposed.  Very few building HVAC systems could achieve this objective through higher ventilation alone and, even if possible, would produce a much higher heating and cooling cost.

 

Understanding Essential Elements of ASHRAE Standard 241 and TSI’s Role in Supporting the Standard

Building managers must develop a plan to shift their building into a higher performance IAQ mode during a pandemic risk period.  To attain compliance, they must verify performance of this enhanced mode prior to an actual event.  TSI solutions can help building managers both make assessments of building’s current state and test the performance of the enhanced IAQ mode. 

Existing buildings are required to perform a series of functional performance tests that are essentially a re-commissioning of the building’s ventilation and filtration systems.  New buildings must be tested in this mode prior to occupancy.

• Supply, return, and outdoor airflow must be measured to ensure that required airflows are provided. 
  A TAB report is acceptable if it is no older than 3 years.  If enhanced ventilation is required for the higher performance mode, an air balance report is required with the building operating in that mode.  
  TSI has a comprehensive instrument portfolio for TAB certification. 
   
• If the building’s air cleaning devices were not certified by the equipment manufacturer both for performance (e.g. AHSRAE 52.2) and safety (e.g., ISO 14644), they must be tested using Appendix A guidelines. 
  These performance tests challenge the filter with an aerosol and measure particulate reduction downstream.  This testing must be performed by an independent, ISO 17025-accredited lab approved by the regulatory authority. 
  TSI is a leading supplier of these filter performance testing components. 
   
• In-room air cleaners are required to be tested for noise safety.  
  Sound level increase must be less than 20 dB at 1 meter from the air cleaner.  A Quest™ Sound Level Meter can be used to measure the intensity of sound in decibels (dB). It helps you gauge the loudness or sound pressure level (SPL) of a particular environment or source. 
   
• All sensors used in air delivery systems, such as flow sensors and CO₂, must be checked against a standard instrument every two years. 
  The Q-Trak™ XP indoor air quality monitor serves perfectly as a CO₂ sensor check in DCV systems, where as the VelociCalc® multi-function ventilation meter could verify flow rate sensors.

For new and existing buildings, operators have the option of either performing the functional performance tests described above or applying a new in-place test of air cleaning performance.  This test requires an aerosol generator and 5 aerosol detectors collecting measurements of particulates with different analytics. 

What tools does TSI have to support your data? We have developed a TSI Link™ Report Creator template that allows you to import .csv data from TSI's Optical Particle Sizer (OPS) 3330 detectors to perform this test. 
 

FAQ's

Are there regulations in place requiring ASHRAE 241 compliance?	No, the standard is quite new and no regulations are in place.  But the Wall Street Journal reported that New York City is considering such regulations.
What aerosol detectors meet the performance requirements for the in-place air cleaning test?	The TSI 3330 and TSI A100 both meet the ASHRAE 52.2 and ISO 12501-4 requirements.
What aerosol generators meet the performance requirements for the in-place air cleaning test?	The Large Particle Aerosol Generator 8108 produces the broad particle size range required for this test.
Data analysis of the in-place test in Appendix C is very complex.  What tools do you have to make this more efficient and less prone to error?	We have a Report Creator template that makes data analysis easy and effective.
I know that TSI has very good ventilation test products?  What do you know about ASHRAE 52.2?	TSI is a recognized leader in aerosol generation and detection.  Air cleaning manufacturers have used our equipment to certify their products since the inception of the standard.
Can I use OmniTrak PM sensors for the in-place test?	No, we do not believe these lower-cost sensors meet the performance requirements of this test over the broad particle size range of 0.3 to 10 um.
Can the new in-place test be applied to all situations?	If the area employs pathogen disinfection-based air cleaning like UVGI, the in-place test is not appropriate.  These air cleaning techniques do not remove particles, they deactivate the pathogen.

 

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