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Fume Hood Safety & Testing

Posted by: Nick Rose, Commissioning & Lab Certification Technician

Fume hoods are the work horse of the laboratory testing field. Used for everything from storage to active chemistry these life saving devices allow operators to work with potentially harmful chemicals to create the everyday items that improve people’s lives. Often, however, owners and operators know very little about how these devices are balanced and certified.

Laboratory fume hoods are balanced to meet industry safety standards designed to keep workers safe during even the most critical chemical processes. From installation to end of use, these devices are tested and retested to ensure they provide the necessary controls. The tests for these safety devices are rigorous and must meet many criteria to achieve certification.

The first test involves checking inflows for average velocity to make sure they are within the ranges deemed safe for operation, and that the sash height is appropriate for the required velocities. Cross drafts are taken to ensure no supply vents are creating potentially unsafe drafts that could pull harmful vapors from inside the cabinet out.

Next, a visible smoke source is passed along the bottom edge of the opening, around the entire access opening, inside the hood along the work surface, and along the back. Since every application is different, these smoke tests are crucial to making sure each operational setup and process does not affect the overall performance of the hood in a way that compromises its purpose. During the test, a certified fume hood technician looks for refluxing and lazy air within the cabinet, and any reverse flow at the access opening. Using this they can definitively say that the predetermined airflows are accomplishing the containment that is so vital for laboratory safety and process integrity.

The last test is performed when a new fume hood is installed, when any changes are made to the exhaust system, or when seeking ASHRAE 110 certification. This test is a tracer gas test. A trace amount of gas is released within the fume hood and scanned for any traces outside the fume hood. The sash is opened and closed, and the gas generated from multiple locations within the hood. A mass spectrometer looks for the gas outside of the hood. This test identifies any possible exposure points and is the final most stringent test to verify safety and achieve certification.

Midwest Associates’ experienced fume hood and ASHRAE 110 certified technicians perform these tests and provide owners with detailed reports and certifications. To see our full range of services, click here.

SMACNA Excellence Award

Congratulations to Midwest Associates Test & Balance Supervisor Joe Seagraves for being recognized for his expertise and leadership in the TAB field! Joe was honored with an Excellence Award at the recent Labor Appreciation Dinner by SMACNA, the Sheet Metal Contractors Association of Central Indiana!


Along with his 40 years of field experience as an air and hydronics balancer, Joe is certified for HEPA Filter Integrity Testing and Biosafety Cabinet Certification and decontamination. He manages projects for multiple clients, working with project managers, engineers, and operations personnel. Joe uses his expertise to guide MWA’s qualified technicians to perform their work and deliver results.


Joe’s dedication to excellence in Testing, Adjusting, & Balancing continues to inspire our entire team!