Emergency Room Exhaust

[tys90]

According to the AIA 2006 Guidelines for Design and Construction of Health Care Facilities, ER waiting rooms must have all air exhausted directly to the outdoors with two exceptions. The exceptions are such:

"If it is not practical to exhaust the air from the airborne infection isolation room to the outside, the air may be returned through HEPA filters to the air-handling system exclusively serving the isolation room"

And

"In a ventilation system that recirculates air, HEPA filters can be used in lieu of exhausting the air from these spaces to the otuside. In this application, the return air shall be passed through the HEPA filters before it is introduced into any other spaces."

I have an application that lends itself to recirculating the air instead of exhausting to the outside. One question is where is the appropriate location for the HEPA filter? The exceptions are vague on the exact location of the filter in the airstream and I can think of several that make sense. My main concern is what is acceptable as far as mixing air streams before HEPA filtering.

Second, these exhaust rates are constant, but the system is a VAV system. So when the AHU throttles back you still need to return the required CFM from the ER waiting rooms. Again, I can think of several ways to control the return that may work but each has their drawbacks. Suggestions welcome.

 

[cry22]

You've got a heavy penalty in cost and additional static pressure with HEPA.
Nothing beats exhaust. I would find a way to exhaust, and there is always a way, always.