A chemical fume hood after a move: why it needs testing and who does it

Why a hood needs testing after a move

A chemical fume hood protects the person working at it: a fan draws air out of the hood and carries the vapours outside through a duct. At the new site the hood is connected to a different exhaust duct, with a different length, bends and fan. Its position in the room matters too: a door, an air-conditioning vent or a busy walkway near the hood creates air currents that disturb the airflow. So even a hood that passed its test in the old lab needs a new test before work resumes.

What the tester checks

• Face velocity: measured at several points across the opening, with the sash at its working height, and averaged.
• Uniformity: no point should deviate much from the average. American guidance flags any point more than 20% off the average.
• Smoke test: safe smoke should be drawn in and not escape.
• Low-flow alarm: that it works.
• Documentation: a sticker on the hood with the test date and result, and a report for the lab.

The numbers

The American standard ANSI/ASSP Z9.5 suggests 80 to 100 feet per minute at the hood opening as a starting point, about 0.4 to 0.5 metres per second. The final target is set by the type of work and its hazards, and older guidance cites 80 to 120 feet per minute. The value that applies to you is set by your institution's safety procedures and by the tester.

When else hoods are tested

• At least once a year, under the American standard.
• After changes to the exhaust or air-conditioning system.
• When the low-flow alarm goes off, even if it clears by itself.
• When there is a chemical smell in the room or complaints from staff.
• When the sash, baffles or duct connection are damaged.

Scheduling the test with the move

• The lab removes the chemicals and cleans the hood according to its procedure, before the moving crew arrives.
• A technician on the lab's behalf disconnects the hood from the exhaust duct, power and any gas, water or vacuum connections.
• Connections are labelled and the last test report is kept, for comparison later.
• A date for the test at the new site is agreed with the tester in advance, right after the hood is placed and connected.

Who does what

We do not test fume hoods. The test is done by a qualified tester on the lab's behalf, according to the institution's safety procedures. We separate the hood from its base, pack it, move it upright in a truck with shock absorbers and place it where it was planned. If you do not have a tester, we are happy to give you the phone number of a qualified technician we know.

More about moving fume hoods

• How to move a chemical fume hood safelyHow to move a fume hood: decontaminate, disconnect exhaust and gas, measure the route, move it upright and test airflow after reinstallation.
• Biosafety cabinets after a move: why recertification is neededWhy a biosafety cabinet (BSC) needs recertification after it is moved, what is tested, and how the lab can plan the test to avoid delays.

More guides

• How to move a chemical fume hood safelyHow to move a fume hood: decontaminate, disconnect exhaust and gas, measure the route, move it upright and test airflow after reinstallation.
• Biosafety cabinets after a move: why recertification is neededWhy a biosafety cabinet (BSC) needs recertification after it is moved, what is tested, and how the lab can plan the test to avoid delays.
• Moving a laminar flow cabinetHow to move a laminar flow cabinet (clean bench): protecting the HEPA filter, removing the stand, upright shock-free transport, and airflow and filter integrity testing before work resumes. Plus how it differs from a biosafety cabinet.