[UPDATE] ASHRAE Increases Filtration Requirements for Surgical Spaces

By Katie Lee | Nov 05, 2020

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This article was updated in January 2022 to incorporate subsequent addenda to ASHRAE 170-2017. New information is italicized. Since this article’s original publication in November 2020, the 2021 version ASHRAE 170 has been released. It incorporates the changes described here.

Key Takeaways

  1. A new addendum to ASHRAE Standard 170-2017 updates filter requirements for numerous healthcare spaces.
  2. The biggest change is to surgical spaces, which now need MERV-16 or HEPA filtration. The level of filtration varies based on the space type.
  3. The higher filtration requirements can impact a project’s budget and HVAC system operation, so they need to be accounted for early in a project.

The latest addendum to ASHRAE Standard 170-2017 (Ventilation of Health Care Facilities) updates filter requirements for numerous healthcare spaces. The most significant changes involve increased filtration for operating rooms and C-section rooms. These new filter requirements have important implications for project budgets and HVAC system operation.

Overview of the New Filter Requirements

In Addendum A (opens as a PDF), ASHRAE updates the minimum filter efficiencies for inpatient, outpatient, and residential health facilities. Some spaces now need a higher level of filtration, some can have a lower level of filtration, and some remain the same. Additionally, Standard 170 removed the terms “Filter Bank 1” and “Filter Bank 2” from Section 6.4 (Filtration) but retained requirements for pre-filters and final filters.

Addendum A was released in September 2020. The new filtration requirements apply to any healthcare project from that point forward that is being designed to the 2017 version of ASHRAE 170. As noted above, these requirements have been incorporated into ASHRAE 170-2021.

New Filter Requirements Have the Biggest Impact on Surgical Spaces

The updated filtration requirements have a significant impact on surgical spaces, which now need MERV-16 or HEPA filtration. Spaces requiring MERV-16 filters include:

  • Operating rooms
  • Operating/surgical cystoscopic rooms
  • Cesarean delivery rooms
  • Outpatient surgical facility operating rooms
  • Inpatient and outpatient Class 3 imaging rooms (added in a later addendum)

Additionally, operating rooms and Class 3 Imaging Rooms used for the following functions now require HEPA filtration at the terminal device (see 7.4.1c):

  • Orthopedic procedures
  • Transplants
  • Neurosurgery
  • Dedicated burn unit procedures

Given this requirement, I think we’re going to see a trend of healthcare organizations installing HEPA filters in a majority of their ORs. This way, they have the appropriate filtration in place no matter what they use the operating room for.

Finally, some nonsurgical spaces now require HEPA filtration: combination AII/PE anterooms, PE anterooms, and wound intensive care spaces (burn unit).

What Does This Mean for My Building?

Budget. The higher-rated filters are more expensive (though MERV-16 filters may provide energy savings). This cost needs to be part of the scope and budget for projects. Additionally, because filters can affect overall HVAC system operation (see below), a healthcare organization may need to make HVAC system upgrades as well.

System impact. This factor is especially relevant to renovation projects. Since air filters affect airflow, healthcare organizations need to verify that their existing HVAC system can function properly with the higher-rated filters.

In our research, we found a MERV-16 filter for air handling units (AHUs) that has a comparable pressure drop to a MERV-14 filter, so where MERV-16 is called for, a swap is possible. However, depending on the existing filter type, it might be a different style than the current MERV-14 filter.

Where HEPA filters are required, swapping out filters might not be possible. The air handling system pressure will first need to be evaluated for the increased pressure drop of a HEPA filter. This applies whether the filter is installed at the AHU or at the diffuser. If the AHU system pressure is not sufficient, then system upgrades may be needed. In some facilities’ operating rooms HEPA filters may already be installed, so this requirement shouldn’t have an effect on their systems.

Maintenance. If HEPA filters are provided at the diffusers, the healthcare facility needs to maintain all the locations where the filters are installed.

With these new design requirements, filtration needs to be an early discussion point during the design process so that it’s captured in the project scope and budget.

Questions about how the new filter requirement applies to your facility or project? Contact us.

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Katie Lee

Katie Lee specializes in healthcare engineering and has contributed to hundreds of healthcare projects, with a focus on designing new systems for legacy buildings. Katie is an expert in ventilation for healthcare facilities, a topic she has presented on both nationally and locally.
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Eric Priest

How often should HEPA filters be changed in the ORs?

Katie Lee

In the appendix of ASHRAE 170, it indicates that filters shall be replaced or maintained per manufacturer recommendations. Typical recommendations are that the filter should be replaced once the pressure drop is 1.5 or 2 times that of the initial pressure drop of the filter.

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