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Are you ASHRAE Standard 241 curious?

ASHRAE Standard 241 is on its way. Here are its 5 biggest takeaways.

As we wait for the final ASHRAE Standard 241 to be published, we wanted to share some takeaways we picked up during the public review period. While it is unclear what individual points may land in the final version, these high-level takeaways reflect the standard’s general intent.

The 5 biggest takeaways:

1. Standard 241 is about ensuring a consistent level of indoor health across ALL indoor spaces—new and old.

2. Creating an SOP for a heightened state of pathogen alert will not only be required but tested and validated against heightened state requirements for ECA.

3. A new term, equivalent clean air (ECA), is a more comprehensive view of air health and considers not only airborne particles but also the number of occupants in the room and if they are at a higher risk (children, elderly, immune deficient, etc.).

4. The standard includes a range of options and alternatives to allow building owners and designers to meet these new requirements in a flexible and cost-effective way.

5. The new standard places a greater emphasis on building operations and maintenance with requirements for regular system inspections, maintenance, and performance testing than it was in the past.

ASHRAE Standard 241 is about mitigating long-range, long-term infection risk.

The impetus for this new standard was addressing one of the primary vehicles of infectious aerosols (eg: COVID, RSV, Influenza, etc.) transmission to prevent the possible spread of future, highly contagious viruses in indoor spaces. While viruses like COVID are transmissible via a range of circumstances, like touch, close-range droplets, and long-range risk (which is essentially only a few meters from an origin source), Standard 241 was developed to tackle the latter, which can be solved by a comprehensive ventilation and disinfection strategy driven by emerging technology, such as Poppy BreatheScore. Essentially, Standard 241 was developed to:

  1. Make infection risk even across ALL indoor spaces. Experts and leading scientists determined that a 5% or lower transmission risk is tolerable to prevent the spread of illness. This percentage was determined by EOCHi, a measurement of ventilation per person within indoor spaces (varying by space, building, or activity).

  2. Mitigate long-range (within a few meters) infections at the building via various methods: HVAC, natural air, filtration, disinfection, etc.

For the first time, this standard ensures that indoor risk is consistent and all places we frequent, such as work, stores, schools, daycares, gyms, and even homes, have a standard level of safety—even when circumstances are unpredictable and occupancy levels change.

What is guidance for ensuring risk remains at 5% or lower?

In the new standard, ASHRAE lists several actions an organization must take to ensure risk is reliably and accurately measured so that environments stay within a range of tolerable indoor risk. However, building owners and businesses do not need to do this alone. ASHRAE suggests that using a professional service to accurately measure eACH across a building's spaces (room-by-room/zone-by-zone) is the simplest and most cost-effective way to determine levels of air health based on occupant usage and capacity, as well as any mitigation factors that prevent airborne pathogens from lingering indoors.


Poppy provides highest accuracy measurements to monitor, certify, and quantify hourly air changes in zones, closed spaces, floors and buildings. Digital accuracy and instant readings to drive energy efficiency and indoor air safety.


Here are a few thoughts on the new ASHRAE Standard 241, Control of Infectious Aerosols (also known as Standard 241).


About Poppy.

Poppy uses patented sensor technology to collect and interpret spacial airflow data in minutes, from measuring eACH and ECA to identifying over-ventilation and under-ventilation. Poppy partners with building owners, facility managers, and companies to quickly uncover ways to optimize, save energy costs, and align to new standards.

Partner with us to uncover ways to improve air health, optimize ventilation, sustainability, and reduce energy consumption and costs.


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