ASHRAE Journal - September 2010 - 78

The Pressure Is On
By Joseph W. Lstiburek, Ph.D., P.Eng., Fellow ASHRAE

It is actually a pretty easy assignment in principle. Find the wet spot and figure out how the wet spot is connected to the ospitals are not fun places to work in, and they are not patient. fun places to build and design or to fix and repair. The The hospital was amazing. It was clean, efficient, and modern. stakes are often high. Nothing is more sobering than Everyone knew what they were doing—from the maintenance when someone dies because of a mistake, especially when the staff to the doctors. Everyone. It was the first time I was exposed mistake does not seem to be a big deal. Actually, a couple of to a team—a real team—not some garbage description from a mistakes. Each one was not such a big deal, but when taken management consultant. together, they became a big deal. Where to start? Just like any building investigation, first I learned about mold the hard way. The experience made determine if there are any patterns. One of the first questions me want to stay away from hospitals. First, take an immuno- I asked was where had the patients died? The team looked at compromised patient. In my case, the patient was an organ me as if I was from a different planet. Not a different planet. transplant recipient. Expose the patient to an opportunistic “Just Canada,” I said. pathogen going by the name of aspergillus fumigatus. This Did the patients die on one side of the hospital more than on mold can overrun an immunoanother side of the hospital? compromised patient’s defenses One of the doctors growled, leading to aspergillosis and to saying he knew it was a mistake death. It is the leading cause to get me involved. What a of death in acute leukemia and stupid question. Right. Except organ transplant recipients. At that the southwest corner was the time I was involved, much where the action was happenearlier in my career, AIDS was a ing, and the race was on. death sentence, and aspergillus It was a classic reservoirfumigatus was often the straw cladding-solar-driven-moisthat broke the camel’s back. ture-vapor-barrier-on-theAspergillus fumigatus grows wrong-side-of-the-assembly on certain building materials, problem. But, it had a twist and that is where I came into that changed my career directhe picture. tion. Check out Figure 1. The Figure 1: Hospital Wall. Classic reservoir-cladding-solar-drivenIt’s been 20 years, and even hospital building enclosure was moisture-vapor-barrier-on-the-wrong-side-of-the-assembly problem. today I can’t say too much for a brick veneer with a masonry obvious reasons. I got a call from someone who said it was block backup wall. Mistake one: no water control layer on the important—a matter of life and death—and for the first time exterior of the block backup wall (see Lstiburek, J. 2006. “UnI didn’t laugh. When one person dies from aspergillosis, it derstanding drainage planes.” ASHRAE Journal 48(2):30 – 35 or must be reported to the Centers for Disease Control and Pre- http://tinyurl.com/drainageplanes). The masonry block backup vention in Atlanta. When two people die, it is considered an wall was insulated on the interior with semi-rigid fiberglass epidemic. There was an epidemic in a mixed climate hospital insulation. Mistake two: a foil-faced vapor barrier installed on east of the Mississippi River and north of the states that lost the interior of the semi-rigid fiberglass insulation. Mold grew the Civil War. on the paper reinforcing of the foil vapor barrier. Guess what Could I get on a plane tonight? When you get a call like that, type of mold? Yes, aspergillus fumigatus. There it was: the mold you get on the damn plane. Actually, I drove, because I could reservoir and amplification site. But, how did the mold get from get there faster. there and inside the patient? My task was to find where the aspergillus fumigatus was The patient rooms were positively pressurized relative to both coming from. The autopsies showed it was growing inside of the outside and the corridors. It was a beautiful system: continupatients. The patients didn’t come into the hospital with it grow- ous preconditioned air from rooftop units injected directly into ing inside of them. They were exposed to it inside the hospital. each room. Wow. The pressure control was perfect, and continu-

ASHRAE Journal

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September 2010

ASHRAE Journal - September 2010

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