Fume Hood Testing & Certification

Fume hood certification is the measured verification that a laboratory chemical fume hood is providing the face velocity and containment performance required to protect researchers from chemical exposure. dL Flow Tech is an independent, NEBB-certified firm that has performed fume hood testing and certification across the Hudson Valley since 1982 — including laboratory projects at Pepsi's R&D campus in Valhalla and institutional research facilities throughout the region. We measure what the safety program requires and document it in a report that stands up to EHS audit.

What is fume hood certification?

A chemical fume hood protects laboratory personnel by capturing chemical vapors, aerosols, and particulates at the face of the hood and exhausting them out of the building before they reach the researcher's breathing zone. Certification is the documented proof that the hood is performing that function — that the face velocity is within the required range, that airflow is uniform across the sash opening, and that the hood is actually containing what it's supposed to contain.

Certification is not a one-time event. Fume hood performance degrades over time as the HVAC system changes, the building loads shift, and mechanical wear affects exhaust volumes. Annual certification is the standard cycle for most laboratory safety programs, with immediate retesting required any time the laboratory HVAC system is modified or the hood is relocated or serviced.

What fume hood testing measures

Face velocity

Face velocity is the speed of air entering the hood opening at the sash face, measured in feet per minute (fpm). The required face velocity is set by the laboratory's safety program and the applicable standard. ANSI/AIHA Z9.5 recommends a minimum average of 80–120 fpm; many institutional programs require 100 fpm minimum. Low face velocity means chemicals can migrate out of the hood. High face velocity can cause turbulence that actually degrades containment.

We measure face velocity using a calibrated anemometer across a defined grid of points at the standard operating sash height. The test records the minimum, maximum, and average velocity, and confirms the uniformity across the opening — a low reading at one corner is as important as the average.

Flow visualization

Smoke or tracer vapor is introduced at the hood face to visualize the airflow pattern. Flow visualization confirms that air is entering the hood cleanly and not spilling out at the sides or corners, and identifies any turbulence or dead zones that would compromise containment.

ASHRAE 110 containment testing

The ASHRAE 110 standard is the most rigorous performance test for fume hoods. Its central element is the AM (as manufactured/as installed/as used) tracer-gas containment test: sulfur hexafluoride (SF₆) is released inside the hood at a fixed rate with a mannequin positioned in front, and a detector measures the concentration at the breathing zone. The result is a direct measurement of how much of the test gas escapes — the AM value — compared to the standard's pass criterion. A hood that passes ASHRAE 110 containment testing is demonstrably protecting the researcher, not just moving air.

VAV fume hood certification

Variable-air-volume (VAV) fume hoods modulate exhaust flow to maintain face velocity as the sash is raised or lowered, saving energy compared to a constant-volume design. Certifying a VAV hood requires confirming that the controller is tracking correctly — that face velocity is maintained within the required range at all sash positions, and that the VAV system doesn't conflict with the room supply-and-exhaust balance that maintains the room at negative pressure relative to the corridor.

VAV hood certification must be coordinated with the room's air balance. A hood that passes face velocity in isolation may fail when the room is balanced, because the room's supply and exhaust interact with the hood exhaust at every sash position. We perform fume hood certification as part of the broader laboratory TAB scope where the full interaction can be verified.

When fume hoods need testing

• Annual certification cycle — most laboratory safety programs require face velocity measurement annually.
• After any HVAC modification — changes to the supply, exhaust, or make-up air system can affect hood performance. Retest after any work on the laboratory air system.
• After the hood is serviced or relocated — physical changes to the hood or its connections require re-certification.
• New construction or renovation commissioning — fume hood certification is part of commissioning a new or renovated laboratory.
• Following a safety complaint or near-miss — any report of unusual odor, smoke reversal, or chemical exposure should trigger immediate testing.
• Before EHS audit or accreditation visit — current certification records are expected by institutional EHS programs and laboratory accreditation bodies.

What your certification report includes

• Hood identification, location, and type for each unit tested.
• Face velocity grid readings — minimum, maximum, average — and pass/fail against the applicable criterion.
• Flow visualization results and any anomalies observed.
• ASHRAE 110 AM test results where included in scope.
• VAV controller verification data where applicable.
• Instrument calibration records.
• Signed certification and deficiency list for hoods requiring repair or reconfiguration.

Service area

dL Flow Tech performs fume hood testing and certification from New York City north through the Hudson Valley to Albany — Dutchess, Westchester, Orange, Putnam, Rockland, and Ulster counties, the five boroughs, and the Capital Region.

Frequently asked questions

What face velocity is required for a fume hood?

The minimum face velocity is set by the laboratory safety program and the applicable standard. ANSI/AIHA Z9.5 recommends 80–120 fpm at the working sash height; many institutional programs specify 100 fpm minimum. Uniformity across the sash opening matters as much as the average.

What is the ASHRAE 110 test?

ASHRAE 110 is the performance test method for laboratory fume hoods. It includes face velocity measurement, flow visualization, and a tracer-gas containment test (the AM test) that directly measures how much of a surrogate chemical escapes into the room. It is the most rigorous standard fume hood test available.

How often should fume hoods be tested?

Most laboratory safety programs require annual face velocity certification. Hoods should also be tested after any HVAC change affecting lab exhaust, after servicing or relocation, and whenever a user reports abnormal smoke behavior or odor breakthrough.

Can a fume hood pass face velocity and still fail containment?

Yes. Face velocity is necessary but not sufficient. A hood can achieve 100 fpm average and still fail the ASHRAE 110 tracer-gas test due to turbulence, cross-drafts, or sash position. Containment testing is the only way to measure actual protection.

Do you test VAV fume hoods differently?

Yes. A VAV hood modulates exhaust volume to maintain face velocity as the sash changes. Testing must confirm the VAV controller is tracking correctly — that face velocity is maintained at the target across the full sash range.