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Biological Safety Cabinets - Balancing Safety with Environmental Concerns

With most manufacturers providing solid biological safety cabinets (BSCs), total cost of ownership has become a hot-button issue with purchasers. Until around 2000, exhaust fans were driven by AC permanent split capacitor motors. Manufacturers gradua

With most manufacturers providing solid biological safety cabinets (BSCs), total cost of ownership has become a hot-button issue with purchasers. Until around 2000, exhaust fans were driven by AC permanent split capacitor motors. Manufacturers gradually switched to more advanced variable frequency drive AC motors that provided greater motor speed control. These have been standard for the last three or four years.


Since older motors did not compensate for filters clogging over time, airflows decreased between annual certifications, compromising contamination control and user safety. In newer cabinets, motors speed up to maintain a constant air velocity into or out of the cabinet. “The coolest thing about them is they are anywhere from 50 to 75 percent more energy efficient than the older models […] and they’re much safer,” says David Phillips, a technical applications specialist at Thermo Fisher Scientific (Asheville, NC).

Although the new motors are costlier than older models, this has not been reflected in the overall price of a new BSC, Mr. Phillips adds. Energy savings can be as high as $800 per year per cabinet.

Environmental consciousness has become a major driver behind abandoning AC motors for DC designs. But as Mike Martin, general manager at ESCO Technologies (Hatboro, PA) notes, the AC-DC issue is far from straightforward. “DC motors draw fewer amps when filters are new or clean. AC motors draw higher amps with clean filters, but fewer as the filters load.”

Regardless of motor type, BSCs should have a means of compensating for filter loading, and provide enough reserve motor capacity to maintain at least 90 percent of maximal air flow as filters clog. Otherwise safety is compromised and downtime increases due to the need for more frequent decontamination and filter changes.

Unlike most laboratory products, BSCs are not “user serviceable.” Since filters often harbor biohazardous material, they are swapped out regularly by accredited, certified, third-party service professionals who also decontaminate the BSCs, adjust any settings required due to installing fresh filter media, and certify the cabinet is operating properly. Certification involves written and practical testing, continuing education, and periodic retesting.

One thing technicians are doing a lot less of these days is replacing motors. Older designs were rated at 10,000 to 15,000 hours of service before requiring rebuilding or replacement. In the last few years, motors rated at 50,000 hours and higher— Thermo claims 100,000 hours—have become standard.

Perhaps the most critical feature is external exhaust. Cabinets that handle toxic gases require venting, but some labs may specify venting for general safety purposes.

External exhausting significantly raises the complexity of designing and building the BSC and entails a “hidden” cost for facilities in terms of the removal of expensive conditioned air.

Modern BSCs come in standard sizes with much improved usability compared to a decade ago. Manufacturers have implemented ergonomic improvements, such as slanted fronts, to provide greater accessibility. Buyers should look for NSF certification, energy consumption and service requirements.

And, as Martin suggests, since test documentation may be hard to come by, they should ask a lot of questions.

NordicSafe NC2-4L8 Class II Microbiological

  • Has the lowest noise MSC in industry at 51 dBA
  • Includes ECM Blower for low energy consumption
  • Provides users with half - speed mode
  • Zero volt relay contact
  • Features QuickstartTM and RS 232


Purifier® Logic® Class II

  • Includes a built-in electronically commutated motor, or ECM, which acts as the brain of the cabinet; it is programmed to precisely control the cabinet’s airflow
  • Constant Airflow Profile (CAP) increases accuracy, reliability, and the elimination of periodic recalibration of airflow sensors to ensure proper airflow by tenfold
  • ECM design is 60 percent more energy-efficient than other types of motors


CellGard 480 ES Class II

  • Also available in the 477 and 475 models
  • Contains TouchLink BSC Control Center
  • DECON101-ready
  • Includes optional password protection and optional Night-Setback switch
  • Features 10° Sloped Sash


1300 Series A2

  • Now available in three and five-foot widths that maximize internal work space while minimizing the external footprint
  • Feature the new NSF-approved SmartPort
  • Choice of stainless steel or SmartCoat interiors and eightinch or ten-inch work apertures
  • Digital Airflow Verification (DAVe) system increases safety

Thermo Fisher Scientific