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Chapter 7: Maintenance & Certification

Changing HEPA Filters

Be sure to familiarize yourself with your operation and maintenance manual.

HEPA filters, whether part of a building exhaust system or part of a cabinet, will require replacement when the airflow is no longer sufficient and filter load has reached a capacity. Filters must be decontaminated before removal. To contain the formaldehyde gas typically used for microbiological decontamination, exhaust systems containing HEPA filters require airtight dampers to be installed on both the inlet and discharge side of the filter housing. This ensures containment of the gas inside the filter housing during decontamination.

Access panel ports in the filter housing also allow for performance testing of the HEPA filter.

HEPA filters are typically constructed of paper-thin sheets of borosilicate medium, pleated to increase surface area, and affixed to a frame. Filters may be constructed as separator-less or contain aluminum separators for stability.

A bag-in/bag-out filter assembly can be used in situations where HEPA filtration is necessary for operations involving biohazardous materials and hazardous or toxic chemicals. This protects the technician handling the filter as well as the environment.

The bag-in/bag-out system is used when it’s not possible to decontaminate the HEPA filters with formaldehyde gas, or when hazardous toxic chemicals have been used in the BSC.


The bag-in-bag-out (BIBO) requirement must be identified at the time of purchase and installation; a BIBO assembly (available only on B1 & B2 Cabinets) cannot be added to a cabinet after the fact.

Certification and Annual UV Light Check


A Biological Safety Cabinet MUST be certified by a qualified individual at the following times:

  • Initial Installation It is extremely important that all new Biological Safety Cabinets be certified when they are received from the manufacturer. Failure to do so may lead to the use of a cabinet which is not functioning appropriately and cause the owner to pay for repairs which should be covered under the purchasing agreement.
  • Moved or Relocated Relocating a BSC may break the HEPA filter seals or otherwise damage the filters or the cabinet.
  • After a Major Repair, such as replacement of HEPA filters or motor.
  • Annually. Each BSC should be tested and certified at least annually to ensure it is operating properly

On-site testing following the recommendations for field testing [NSF/ANSI 49-2011 (Annex F) or most current version] must be performed by experienced, qualified personnel. Some basic information is included here to assist in understanding the frequency and kinds of tests to be performed.

Use Accredited Field Certifiers

It is strongly recommended that accredited field certifiers be used to test and certify Biological Safety Cabinets whenever possible (List of NuAire Qualified Certifiers). If in-house personnel are performing the certifications, then these individuals should become accredited. The importance of proper certification cannot be emphasized enough, since persons who manipulate infectious microorganisms are at increased risk of acquiring an occupational illness when their Biological Safety Cabinets are functioning improperly.

The annual tests applicable to each of the three classes of Biological Safety Cabinets are listed and described below. There is also information regarding the conduct of selected tests. Biological Safety Cabinets perform consistently well when proper annual certification procedures are followed; cabinet or filter failures tend to occur infrequently.

Performance Testing Biological Safety Cabinets in the Field

Biological Safety Cabinets are the primary containment device that protects the worker, product and environment from exposure to microbiological agents. Performance of Biosafety Cabinetry is viable to ensure maximum protection and minimize contamination. Performance specifications have been established by NSF/ANSI Standard 49 for the evaluation of Class II laminar flow biological safety cabinets. Various tests have been established within these standards to confirm your biological safety cabinet is operating at a standard level.

Tests such as down flow and inflow velocity, airflow smoke patterns, filter leak, light intensity, vibration, noise level, and UV light integrity will be performed by an accredited field certifier at least on an annual basis to certify the integrity of your biosafety cabinet system is running at peak performance levels. For more information on how each test is performed please contact NuAire or NSF at

Copyright © 2012 NuAire, Inc.

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