Fume Cupboard Safety: A Day-to-Day Guide for Users
James Cox
Project Manager
Estimated reading time: 5 minutes
A fume cupboard only contains fumes as well as it is used. A perfectly specified, freshly tested cupboard can still fail to protect its user if the sash is left too high, the baffle slots are blocked with equipment, or an alarm is ignored. This guide covers the day-to-day habits that keep a fume cupboard working the way it was designed to.
Before You Start Work
Check the airflow alarm
Confirm the airflow indicator shows a normal, non-alarm state before you begin. Never start work against an active alarm.
Check the sash moves freely
The sash should raise and lower smoothly with no sticking. A faulty sash mechanism should be reported and the cupboard taken out of use until fixed.
Clear the chamber
Remove anything left in the chamber from a previous user before adding your own equipment. A cluttered chamber disrupts airflow before you have even started.
Working Safely at the Cupboard
Good Working Habits
- Keep the sash as low as practical: only raise it as far as you need to carry out the task, and lower it again between steps of a procedure.
- Never work with your head inside the sash plane: keep your face behind the line of the sash opening at all times.
- Position apparatus well back from the sash opening: working right at the front edge gives fumes the shortest possible path out into the room.
- Move slowly around the sash opening: fast hand or arm movements near the opening create turbulence that can pull fumes out into the room, even at the correct face velocity.
- Deal with spills immediately: clean up according to your risk assessment and site COSHH procedures rather than leaving residue in the chamber.
Common Mistakes to Avoid
Things That Compromise Containment
Blocking the baffle slots: the slots at the back of the chamber shape the airflow across the whole working area. Placing tall apparatus, stands, or storage against them disrupts that airflow pattern, even if the sash itself is at the correct height.
Using the cupboard as chemical storage: a fume cupboard is a working space, not a cabinet. Stored bottles and reagents reduce the effective volume, disrupt airflow, and increase the fire and chemical load if something goes wrong.
Overloading with large apparatus: big rigs and equipment that fill most of the chamber leave little room for air to move around them cleanly, creating dead zones where fumes can accumulate.
Ignoring an alarm: an airflow alarm means face velocity has moved outside the range the cupboard was tested to. Continuing to work through an alarm defeats the purpose of having one fitted.
Responding to an Alarm
Every fume cupboard should have an airflow monitor fitted, in line with BS EN 14175-2, Clause 8.2, which requires a means of warning the user when face velocity falls outside the tested range. If the alarm activates:
- Stop work and lower the sash fully.
- Do not continue the procedure until normal airflow is confirmed.
- Check nothing obvious has caused it, an open door or window nearby, another extraction system just switched on, or the sash being raised too high.
- If the cause is not obvious, report it and have the system checked before further use.
Room Conditions Matter Too
A fume cupboard does not operate in isolation from the room around it. A few conditions outside the cupboard itself can disturb its performance:
- Doors and windows near the cupboard: opening a door close to a fume cupboard creates a draught across the sash opening that can disrupt the airflow pattern. Where possible, site cupboards away from doors and busy walkways.
- People walking past quickly: fast movement past an open sash creates turbulence in the same way fast hand movements do, just from further away.
- Other extraction or air handling equipment: switching other fans or extraction on and off nearby can change room pressure and affect face velocity, particularly in labs with several fume cupboards on one system.
End of Session Checklist
| Check | Why it matters |
|---|---|
| Chamber cleared of apparatus and waste | Leaves the space clear and airflow unobstructed for the next user |
| Spills and residue cleaned | Prevents chemical accumulation and cross-contamination |
| Sash lowered fully | Minimises energy use out of hours and protects the chamber |
| Any faults reported | Keeps the cupboard out of use until it is confirmed safe, rather than leaving it for the next person to discover |
These habits do not replace your site's own risk assessment and COSHH procedures, they sit alongside them. If you are training new starters or refreshing a lab's safety procedures, our engineers can also check that your airflow alarms and sash mechanisms are performing as they should.
Not Sure Your Airflow Alarm Is Working Correctly?
Our engineers can inspect, test, and recommission your fume cupboard's airflow monitoring as part of a routine service visit.