By Healthcare Facilities Today

When designing an airborne infection isolation (Aii) room, it is generally accepted that establishing a laminar flow system is desirable. However, achieving the design parameters necessary for this strategy to be effective cannot be assured in practice, putting others at risk for hospital acquired infections, argues an article in Healthcare Design magazine. It is therefore advantageous to consider other ventilation strategies for managing harmful airborne microorganisms. These strategies include increased dilution and removal of contaminated air.

Dilution: The goal of this strategy is to decrease the concentration of the contaminants in the space. "Locate supply grilles or registers directly above the patient bed, consider locating [the] exhaust grille near the head of the bed," says author Ardas Sabuncuyan, assistant director of mechanical engineering with Jacobs Engineering Inc.

To guard against a decrease in airflow due to clogged exhaust grilles and ductwork, these as well as the fan should be oversized, he says. If the exhaust equipment is not kept clear, the room will become overpressurized, reversing from negative pressure to positive pressure. This would defeat the containment strategy of the design.

As well, an Aii room should be supplied with a constant amount of air. If the facility's HVAC system includes VAV boxes, the box supplying the Aii room should be set to remain constant.

Removal: The removal strategy is, of course, to move contaminated air out of the facility to where it will not pose a risk to other people, or filtering the air through a HEPA filter. "To promote dilution, the fan discharge should be directed vertically upward at a speed of at least 2000 FPM," and it should be discharged at least 25 feet away from openings into the building or public spaces, says Sabuncuyan.

The exhaust fan should be labeled in such a way that maintenance personnel will understand it's contaminated air from an Aii room.

Read the full story.