Dehumidifiers, a large industrial desiccant unit, balanced dampers, and reduced air pressure had all been employed as a means of attempting to precisely control humidity in this pharmaceutical specialty and medical device plant’s Class 8 cleanrooms. A device that modulates a DX air conditioning system’s capacity, allowing it to dehumidify the space without overcooling it, proved to be a perfect fit.


John Garbini had tried almost everything. As facility support manager for an assembly plant in Reading, PA, he was stuck with a nagging problem: When the humidity in the plant’s Class 8 cleanrooms wasn’t too high, it was too low.

He had tried dehumidifiers. He had tried a large industrial desiccant unit. Balanced dampers? Reduced air pressure? Been there, done that.

Seeking Balance

Angiotech, a pharmaceutical specialty and medical device manufacturer with more than 1,500 employees worldwide, uses the Reading plant to assemble and package sterile, disposable scalpels and surgical needles with attached sutures.

High humidity in the cleanrooms could not only encourage bacterial growth, it could prematurely degrade a type of moisture-activated suture that is designed to slowly dissolve in human flesh after the surgical incision heals. Low humidity, on the other hand, promotes static electricity, which interferes with computerized packaging and labeling equipment and gives employees small shocks.

“Temperature and humidity swings were normal,” Garbini recalled. “Our employees were either too hot or too cold. It was a challenge to maintain the proper temperature while still dehumidifying the space. The air-handling compressors were constantly slamming on and off, but the main problem was that I could never get the humidity low enough to stay within our specs, which are more stringent than the federal cleanroom standards.”

Rh And Temps Stable

Today, temperature and humidity are holding steady in both Angiotech cleanrooms. The solution came in the form of the APR Control, a device manufactured by Rawal Devices, Inc., of Woburn, MA. The APR Control smoothly modulates a DX air conditioning system’s capacity, allowing it to dehumidify the space without overcooling it. The APR Control varies refrigerant flow according to suction pressure, which changes with the temperature of air crossing the evaporator coil. Because it continuously monitors the heat content of return air, the control maintains the system in a dehumidifying mode more efficiently than thermostats and humidistats and without risk of coil icing, liquid slugging, or excessive compressor cycling.

Garbini learned about the APR Control from Bob Reichenbach, service manager for the Warko Group, Angiotech’s local HVAC contractor. In fact, Reichenbach had been recommending the device for years, but Garbini had not found room for one in his budget.

Finally, Garbini purchased an APR Control along with a new air handler for the troublesome cleanroom (the one where the needles with moisture-activated sutures are packaged). It was installed in late December 2005, when the plant was shut down for the holidays. At last, Garbini was able to keep the room at 20% to 50% rh regardless of the weather outdoors. He calls the device “Little Pauly,” after Paul Gardner, the amiable Warko mechanic who installed it.

 “It made such a significant impact that we installed another one in the air handler for the other cleanroom in May 2006. Now we’re now maintaining humidity and temperature in both rooms well within specs, our employees are more comfortable, and I’ve even seen a decline in the electrical energy consumption,” said Garbini.

The Story Behind The Story

To allay any doubts that the improvements from the first installation were due to the APR Control (rather than the brand new air handler) and to demonstrate its effectiveness once and for all, Reichenbach persuaded Richard Rawal, Rawal’s vice president, to donate the second unit. The results were enough to finally convince Angiotech’s upper management. Garbini recently ordered a third APR Control for the finishing department, where the needles and blades are polished, cleaned, and washed before going to the cleanrooms for assembly and packaging. Though not an official cleanroom, this area requires frequent air changes, HEPA filtration, and, of course, stable temperatures and humidity levels.

“For new additions to the facility, the APR Control will be designed in from day one - that’s a given,” adds Garbini. “I wouldn’t think of installing another air handler without one. I can certainly justify the expense based on the positive benefits that have already been realized.”ES