Fume hoods 3 min read
Compliance with EN 14175, intended use, the chemicals involved and the extract system: the right fume hood is chosen through a risk analysis at the design stage.
A fume hood is a ventilated enclosure that allows any work with chemicals to be carried out safely in the laboratory. It removes contaminants produced during the work, such as acid vapours, heat and process odours, to the outside through the exhaust system it is connected to, and it is also used to remove hazardous aerosols. To provide this protection, the fume hood has to be chosen correctly.
1. Compliance with EN 14175
The first and most important point when buying a fume hood is that it has been manufactured in accordance with TS EN 14175. This should be documented, and on request it should be possible to have an airflow test carried out on the very unit purchased. Units whose airflow dynamics have not been set up to the standard show serious leakage and poor performance; their protection is reduced and may disappear altogether.
2. Intended Use, Chemicals and Dimensions
The second point is the choice of model and specification. What the fume hood will be used for, and with which chemicals and instruments, must be established in advance. Otherwise a fume hood bought with a standard specification may soon become unusable because of the chemicals in use, or may prove unworkable because it needed to be built to special dimensions.
- General-purpose (standard) fume hoods are designed for general laboratory work and are typically used in chemistry, physics and biology laboratories. They can be chosen for laboratories that use lower-risk chemicals.
- High-performance fume hoods should be used for work with hydrofluoric or perchloric acid, or with hot, concentrated mineral acids. The enclosure immediately extracts the acid vapours, heat and process odours generated during the work.
3. What Determines the Level of Protection
The protection a fume hood gives its user depends on its original design and on meeting minimum standards, on its position relative to other equipment, local air movement and the movement of people, on the work carried out inside it and on how it is ventilated. Which type of fume hood to use should therefore be decided through a risk analysis carried out by specialists when the laboratory is designed.
4. Fume Hood Types by Airflow Control
- Constant air volume (CAV): the simplest design. The volume of air exhausted is constant regardless of sash height, so as the sash is lowered the opening becomes smaller and the face velocity rises. The sash should therefore be kept at the optimum height marked on it.
- Variable air volume (VAV): the sash height is monitored continuously and the exhaust volume is adjusted to keep the average face velocity constant within accepted limits. It is the most sophisticated type and needs correct design, installation and maintenance.
- Auxiliary-air fume hood: a separate duct supplies outside air to the face of the fume hood, reducing the consumption of heated or conditioned room air and the associated energy loss. It is designed with the fact in mind that unconditioned air may make the user uncomfortable.
5. Extract System and Services
- The extract system must be able to provide a continuous airflow and run 24 hours a day.
- Electrical installation and equipment must be kept separate from mechanical installation and equipment.
- Electrical sockets and switches must be located outside the working area of the fume hood.
KRCLAB fume hoods are manufactured to TS EN 14175; the range includes general-purpose and high-performance models in a number of widths.
