O3 can potentially compromise laboratory test results as it accompanies the significant quantities of outdoor air required by today’s IAQ public building codes. “Ozone reacts with the cyanine dyes used in labeling RNA for microarray-based gene expression profiling studies and quenches their fluorescent signal,” said Donald Primerano, Ph.D., professor and director of the MCF, Dept. of Biochemistry and Microbiology, Joan C. Edwards School of Medicine, Marshall University.
NEW SCIENCEWhile many facility planners are familiar with HEPA and UV filtration for particulate and biological filtration, those technologies are essentially ineffective against gaseous contaminants such as O3. Primerano and Marshall faculty colleague Goran Boskovic, Ph.D., didn’t record O3 levels in their previous microarray lab, which was a retrofitted space not originally designed for the relatively new discipline of gene expression profiling studies.
However, they suspected O3 might affect the new lab’s research accuracy after reviewing the recently published paper, “Improving Microarray Results by Preventing Ozone-Mediated Fluorescent Signal Degradation,” presented by a major open, integrated gene expression system supplier, Agilent Technologies, Palo Alto, Calif.
When Primerano and Boskovic raised concerns about O3 levels at preconstruction building planning meetings, Byrd’s mechanical-electrical-plumbing systems designer, Scheeser Buckley Mayfield (SBM) Consulting Engineers, Uniontown, Ohio, and design-build general contractor, Mascaro Construction, Pittsburgh, proposed a solution.
Gas-phase air purification is commonly used to filter gaseous contaminants such as aromatic hydrocarbons, oxides of nitrogen and sulfur, and other vehicle emission byproducts at airport terminals and urban buildings. It was determined to be the best solution for reducing O3 in the MCF, according to Michael Wesner, vice president of mechanical engineering, SBM.
(Wesner’s past specification experiences with gas-phase filtration have included an in vitro fertilization laboratory, where air purity was essential to fertilization success, plus a hospital where food odors from a nearby restaurant’s exhaust were infiltrating through the HVAC outdoor air.)
At the MCF, Wesner specified an APS-3000-3VU gas-phase air purification unit by Circul-Aire, a subsidiary of Dectron Internationale, Roswell, Ga. Aside from gas-phase filtration, the unit also includes a 30 percent and a 90 percent mechanical filter.
ISOLATION STRATEGYThe stand-alone unit in the 800-square-foot lab supplements Wesner’s strategy of isolating the room with its own internal air purification unit to treat the air supplied to the lab.
The lab’s supply air is ducted through the MCF’s supply variable air volume (VAV) terminal directly to the gas-phase unit’s return air section. The laboratory supply air is provided by the central station air-handling unit (AHU) located in the mechanical penthouse, dedicated to serving the lab areas in the building. The AHU is a 100 percent outside air unit rated for 150,000 cfm, manufactured by Governair, Oklahoma City.
Like the many other offices, classrooms, and labs in the four-story, 144,000-square-foot building, proper temperature and airflow are achieved via in-duct VAVs from Krueger, Richardson, Texas. The laboratory areas have a VAV supply and exhaust air system. The exhaust air terminals track the supply air terminals, allowing positive or negative airflow for a respective lab, depending on the airflow offset between the supply and exhaust air terminals.
In the case of the MCF, any supply air O3 is absorbed as it passes through the air purification media (carbon-based pellets custom mixed specifically for the MCF’s requirements). Periodically, Marshall’s maintenance staff will send media samples to Circul-Aire’s in-house, ISO-certified testing lab to evaluate its effectiveness and whether it needs replacement.
OPERATION AND PERFORMANCEThe gas-phase unit continually recirculates 1,500 cfm within the MCF, while the facility’s supply air terminal varies from a 500-cfm minimum to a 1,500-cfm maximum.
Since microarray research doesn’t require exhaust hoods, SBM’s design provides a positive, 200-cfm offset between the supply and exhaust air VAV terminals, which results in a 200-cfm positive pressure to safeguard against any O3 infiltration from neighboring spaces.
Tests performed by Primerano’s department with a handheld Aeroqual Series 200 ozone monitor by Kanomax-USA, Andover, N.J., reveal that ozone is approximately 40 ppb (parts per billion) when the gas-phase unit is off, and suppressed below an acceptable 8-ppb level when it’s running. “We’re very satisfied with the 8-ppb level,” said Primerano.
The MCF’s cooling and heating is accomplished with the building’s four-pipe system installed by mechanical contractor Sauer Inc., Pittsburgh. Three 500-ton Carrier chillers and 10 modular boilers by the Patterson-Kelley division of Harsco Corp., supply the system. An Invensys Controls building automation system controls the building.
INSTALLATION DETAILSSince the effects of O3 on microarray labs is a fairly recent discovery, gas-phase filtration was specified late in the project as an add-on. Thus, fitting the 10- by 5-foot gas-phase unit into the lab late in the construction phase was a challenge for Mascaro Construction and the project’s sheet metal contractor, SSM Industries, Pittsburgh. “It was a tight fit in the freight elevator even after taking panels off, plus we had to open up walls to get the unit into the lab,” recalled Mel Miller, senior project manager, Mascaro Construction.
Agilent Technologies and Circul-Aire both recommend 500 fpm of airflow through a gas-phase filter. Although the APS-3000 unit was added into an SBM’s already-designed duct system, Wesner still met the minimum recommendation of 500-feet/minute of airflow through the gas-phase filter.