The purpose of this guide is to describe how the check is performed.
This forms the basis for working safely in the fume cupboard.
Checks on fume cupboards according to DS 457 include, among other things, the following points:
Prerequisites for being able to carry out the check:
- The fume cupboard in question has been reported to be in normal operation.
- The overall ventilation is balanced, and there is a final balancing report.
- The ceiling must be intact, and all doors and windows must be able to be closed.
- The trace gas measurement is performed in the fume cupboard with associated air velocity measurement.
- The trace gas measurement can make image documentation of the fume cupboard arrangement.
Air velocities and flow direction
All measurements of air velocities are made with a directional calibrated anemometer.
The air velocity in the fume cupboard is measured at, for example, 50cm and 25cm work openings, also called high and low hatch openings.
The measurements of air velocities are made with the current cupboard arrangement.
The hatch is set to high and low hatch openings, respectively:
- The dimensions and measuring points of the work opening are stated on the test form.
- Air velocities (m/s) are measured at the measuring points of the work opening and transferred to the test form.
- The average air velocity in the work opening of the fume cupboard is calculated on this basis.
The hatch in the fume cupboard is slowly opened, and it is noted on the test form whether the fume cupboard emits a visual and/or acoustic alarm when the hatch is approx. 5 cm above the mark for the maximum work opening.
It is also checked that the flow alarm of the fume cupboard does not indicate “low flow” at maximum work opening.
The function of the flow alarm is checked and cleaned, so we are sure that it emits an alarm at too low a flow.
For a fume cupboard to be safe to use, some requirements are recommended to be met:
- The air velocity into the fume cupboard is measured, and the average velocity in the entire hatch opening should be 0.5 m/s.
- A trace gas test is performed, and the calculated safety factor for the fume cupboard must be at least 10 (if working with carcinogens in the fume cupboard, see below).
PN Engineering recommends that the requirement for a safety factor of 40 is applied, just as with carcinogens, so that the user is always protected, regardless of which substances are being worked on.
Section 17 carcinogens.
If working with carcinogens in the fume cupboard, the safety factor for the fume cupboard must be at least 40.
DS 457, Standard for fume cupboards, 2nd edition, 1993.
(DS 457 has been removed from the list of applicable standards, but the standard is for safety reasons chosen as a supplement to the requirement for approval according to DS).
The principles in the standard are valid according to Danish law.
Fume cupboards in laboratories - a measurement method, Kjeld Christensen et al., Danish Technological Institute.