Isolation Room Air Filtration Considerations

With every outbreak and “crisis” of a deadly or potentially deadly disease (Ebola, swine-flu, bird-flu, SARS, etc.) we are asked to consult on the filtration for Isolation Rooms. The difficulty is there are multiple types of Isolation Rooms and we have to first identify the objective of the room. Modern technologies have made it easier to incorporate Isolation Rooms in buildings and because they can reduce or prevent nosocomial or hospital originating diseases more hospitals should consider adding them as part of their risk prevention plans.

AII (Airborne Infectious Isolation)/Negative Pressure Rooms are the most common that we get asked about as they pose the biggest threat to staff, other patients, visitors, and staff. These types of rooms are for patients that are able to transmit airborne diseases like Tuberculosis, Pneumonia, and Whooping Cough. The first point of clarification here is that an anteroom is not required, but having one will allow for more flexibility of the space. These rooms need robust exhaust systems to maintain negative pressure in the room and the filter section should contain a bag-in/bag-out housing, bubble-tight damper, and minimum 99.97% HEPA filter. Bag-in/bag-out housings are important here because the bag acts as an additional barrier to the bacteria/virus that has been captured in the filter and the maintenance engineer that is responsible for changing the filters. Adding an additional carbon filter section is also advisable to capture the smallest of particles. Supply air has no additional requirements above and beyond a normal patient care room.

PE (Protective Environment) Rooms are easily the most common as surgical suites could be classified here; these are also for patients that are immunocompromised and cannot handle exposure to fine particles, molecular pollutants, or otherwise harmless organisms. Again an anteroom is not required but is suggested if feasible because it will increase the flexibility of the space. Because of the critical nature of the patient room-side-replaceable 99.99% HEPA diffusers should be used to ensure that the air entering the room last passes through the HEPA filter as the room is kept under positive pressure. The addition of a vertical room air cleaner with molecular filtration should also be considered to remove gaseous pollutants that may irritate people in an immunocompromised condition but not affect a healthy person.

Combined Isolation Rooms are when you have a patient that is both immunocompromised and has a disease that can be transmitted through the air. This is where the extra investment in an anteroom becomes useful as a Combined Isolation Rooms require an anteroom. The anteroom and patient room need to be under opposing pressures, though either is acceptable according to ASHRAE’s Design Manual here is what we would suggest: Keep the anteroom under positive pressure with minimum 99.99% HEPA filtration, this will act as an air curtain protecting any potential airborne pathogens from escaping the Isolation Room and provide HEPA filtered air to the patient care room. The room itself then is kept in negative pressure with the supply air 99.99% HEPA filtered and the exhaust air having a Bag-in/Bag-out HEPA filtration system. Again, the addition of a vertical room air cleaner with molecular filtration should also be considered to remove gaseous pollutants.

Contact Isolation Rooms have no special filtration concerns because the patient’s ailment is not airborne – like Ebola and chicken pox. Any standard patient room can be used as a Contact Isolation Room.