Hospital Air Filtration – Requirements and Best Practices

Hospital Air Filtration – Requirements and Best Practices

Hospitals present one of the most unique and challanging buildings for Air Filter experts.  This is due to the diversity of spaces and the varying requirements and regulations of each of them, from store rooms/closets, to general paitenet care and exam rooms, to surgical operating rooms, and pharmacies.  Here we will be devoid of brands and marketing material and focus solely on the legal requirements and best practices for air filtration in these different areas within a hospital.  All of the requirements for hospital air filtration discussed come from ASHRAE 170 and the latest edition of ASHRAE’s latest edition of “HVAC Design Manual for Hospitals and Clinics

Surgical Suite/Operating Room Filtration:
This is where the most surprises occur in the realm of air filtration in hospitals because many assume that HEPA filters are required for surgical operating rooms, but that isn’t the case.  You aren’t required to have anything more than the same MERV-14  (ePM1 75%) filters that are used in general inpaitent care areas.  However, due to the legal liability of “standard of care” most hospitals install HEPA filters – and I ahve yet to meet a surgeon that doesn’t care if HEPAs are used or not.  Here there is a little variation as well between cleanroom style HEPA filters(which install in teh ceiling) and in-duct or HVAC HEPA filters (that install in the ductwork).  There are advantages and disadvantages of both, but the cleanroom style HEPA filters provide for a safer, cleaner environment (which is why they are used in cleanrooms!) due to their “terminal” nature that the last thing the air passes through before entering the room in a HEPA filter.  When deciding on just how much filtration should be desinged into an operating room think about this: If it were your child being cut open and operated on, what would you want the room to have?

Isolation Room Filtration:
Here the minimum standards/regulations and best-practice are much more in-line with eachother.  There are 4 classifications for Isolation Rooms in Hospitals:

  1. Airborne Infectious Isolation (AII) Rooms These rooms must maintain negative pressure to the adjoining spaces, and typically have laminar flow or some other air pattern that limits the infectious particles/spores from being transmitted, and the exhaust air must be directly ducted outdoors and is commonly HEPA filtered, HEPA filtered exhaust air is only required if the ducting merges with other ductwork.  NO anteroom is required, though having one is highly advised.  It is also advised to help protect the nurses and doctors that will be attending to the paitent by also having an in-room air purifier and upper-air UVC fixture so that any virus, bacteria or other pathogens that originate in the space are controlled.
  2. Protective Environment (PE) – These rooms must maintain positive pressure to adjoining spaces, supply air must be HEPA filtered, laminar or unidirectional airflow is not required but highly recommended, there is no requirement for the exhaust air. NO anteroom is required.
  3.  Combined AII/PE – These DO require an anteroom which must be the opposite pressure to the isolation room, the room with the positive pressure must have HEPA filtered supply air and the room with negative pressure must have HEPA filtered exhaust air.
  4. Contact Isolation Room – No special pressure differential or filtration is required.
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The Labratory spaces in hospitals only require MERV-13 filtration and only need one bank of filters.  If these spaces aren’t large enough to have their own air handler then it is common for them to be supplied with air that is going to Operating Rooms, paitent rooms, or other areas that are being treated with MERV-14 filtered air.

 Class A Surgery:
These minimally invasive surgeries have even lower requirements than surgical suites where class B and C surgery would occur.  Like labratories they only require MERV-13, but best practice would be to have HEPA filtered air supplying these spaces.  98% of hospital aquired bacterial infections are transmitted from the air, so when someone is being cut open, even a little bit, it is best practice to have HEPA filtered air – even if it is in the form of a small in-room unit to help prevent legal issues and ensure medicare payments are not denied.

Other Areas:
Most other area of the hospital, bulk storage, administrative, food prep, laundry, etc. are all only required to have MERV-8 filters protecting them.  In Administrative or other areas where occupants will travel back and forth to paitent care areas small supplemental air purifiers are recommended as an added protection for these employees.  Unitvent, small heat pump, and PTAC style units are required to have MERV-6, which is usually an upgrade form the washable or fiiberglass disposable filters that these units come with when new.

1 Comment
  • Carolyn Meece
    Posted at 11:16h, 15 August


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