Maintaining laboratory equipment during periods of inactivity: Ventilated Hoods & BSCs

Confident scientist in laboratory

The pandemic of 2020 has taught us many things. We were all forced, very unexpectedly, to live and work in unconventional ways. During these times, many issues came up in laboratories that were previously of little concern. For most labs, equipment is used routinely or continuously, and not much thought is given to what would happen if the equipment were to sit idle for an extended period. This article series will explain what can happen if equipment is left idle for long periods, how to prepare equipment for an extended period of inactivity, and how to restart equipment. In this three-part series, we will cover water purification systems and glassware washers, ventilated enclosures, and drying/evaporation systems.

See Part 1: Glassware Washers & Water Purification Systems

Fume hoods

Technicians may want to turn off the fume hood to conserve energy when they are not in use for extended periods of time. However, the fume hood likely plays an integral part in the building HVAC system, and the blower should always be kept on. For example, cleanrooms and laboratory spaces can require six or more air changes per hour (ANSI/ASHRAE, 2019; NSF/ANSI, 2019). The air exhausted from the fume hood helps achieve the required air changes within the space and ensures the building maintains proper directional airflow. We advise asking your building manager or industrial hygienist to see how your fume hood is integrated within the HVAC system before you shut down your fume hood’s exhaust system.

If the fume hood is improperly shut down, several issues can arise. Foremost, a backdraft through the fume hood exhaust system will carry harmful fumes into the working space. This not only poses a health hazard to workers, but fumes could also damage equipment in the area.  Another issue that can arise is rain and other elements can enter the ductwork via the exhaust stack when proper airflow out of the exhaust stack is not maintained. This could lead to water entering the workspace via the fume hood and could damage the building and equipment. The chemical storage cabinets may depend on the same exhaust system as the fume hood for ventilation, which helps protect the cabinetry from corrosive fumes. In this case, the fume hood exhaust should always remain under negative pressure to prevent the accumulation of fumes that could corrode cabinets over time. 

Labconco follows the recommendation of the American National Standards Institute (ANSI), American Society of Safety Professionals (ASSP), and American Industrial Hygiene Association (AIHA) regarding the operation of fume hood exhaust systems. ANSI Z9.5 Section states that “Unless all individual exhausts connected to the centralized exhaust system can be completely stopped without creating a hazardous situation, provision shall be made for continuous maintenance of adequate negative pressure (suction) in all parts of the system”. If you are unsure of how your exhaust system is designed, we recommend you run the fume hood blower continuously. ANSI Z9.5 also states “as an alternative, if the hood is completely turned off, the hood shall be emptied and decontaminated and provision shall be implemented to prevent the hood from back-drafting”. So, should you choose to shut down your fume hood, we recommend the following steps in accordance with this standard. First, ensure the ductwork is equipped with adequate back-draft protection. Next, properly seal and store all chemicals, waste and equipment in approved locations. Then, properly clean and decontaminate the fume hood as per local codes and regulations to ensure hazardous fumes do not enter back into the building space should the backdraft dampers fail. Next, the fume hood should be tagged out of service to avoid inadvertent use. And last, all directional airflows and safe containment of other ventilation equipment should be verified before work resumes.

Biosafety cabinets

A routine daily cleaning practice with biosafety cabinets (BSC) typically involves a wipe down of the cabinet inside with a suitable disinfectant, closing the sash, and turning the unit off. In some cases, turning the UV light on may help with any remaining surface decontamination. For extended periods of shutdown, a BSC should be more robustly decontaminated – including decontamination underneath the work surface plus the exterior surfaces.

If the BSC will be moved into storage, it should undergo a gaseous decontamination before being relocated from its normal installation location. Gaseous decontamination is typically performed by a qualified certifier using either chlorine dioxide, vaporous hydrogen peroxide (VHP), or formaldehyde. Upon return, a thorough assessment of the cabinet should be performed prior to use. The exterior of the BSC should be wiped down with a suitable disinfectant, and the interior surfaces should also be fully disinfected. If the BSC has been moved out of storage, or the certification has elapsed (certification is typically good for one year), the BSC should undergo a recertification before use. For recirculating Type A2 and Type C1 models, turn on the blower and allow the biosafety cabinet to run for at several minutes to purge the interior of contaminants. During this initial warm-up period, ensure the BSC has sufficient filter life remaining and check that no alerts or alarms are active. If the BSC has low filter life, or any alerts or alarms that cannot be resolved, contact a certifier to have the unit recertified before use. Last, perform a final cleaning all interior surfaces with a suitable disinfectant, and wait several additional minutes before carrying out any work (NSF/ANSI, 2019).

Should you have any questions regarding the proper use of your Labconco product, please contact us.



American National Standard Institute. (2012) Laboratory Ventilation (Standard No. Z9.5-2012).

American National Standard Institute/ American Society of Heating, Refrigerating and Air-Conditioning Engineers. (2019) Ventilation for Acceptable Indoor Air Quality (Standard No. 62.1-2019).

National Sanitation Foundation/ American National Standard Institute. (2019) Biosafety Cabinets Design and Performance (Standard No. 49-2019).

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