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Guideline: The safe use of a fume cupboard

Purpose

To set out the guidelines for the safe use of fume cupboards.

Guideline

  1. The fume cupboard is a major means of controlling your exposure to chemicals and other airborne hazardous materials.

Operation

  1. A fume cupboard is basically a ventilated box with an adjustable work opening (sash). A moving curtain of air (at 0.5 ±0.1 m/s) being drawn past the operator, through the opening, over the work, then up the exhaust stack reduces your exposure. A fume cupboard used properly provides adequate protection. However, incorrect use a fume cupboard may result in dangerous material escaping from the cupboard.

See: Demonstration on fume cupboard air flow

  1. A fume cupboard is designed to have a smooth airflow through the front opening (see attached image: Normal airflow into a fume cupboard).
  2. The fume cupboard draws air out of the laboratory. Therefore at least an equal amount of air must be brought into the room to replace it. Please ensure that there is an adequate amount of make-up or supply air into the room before using an exhaust system.
  3. Baffles or slots at the back of cupboard achieve an even airflow through the face of the cupboard. If the baffles or slots are blocked or restricted, then the air distribution can become uneven or unsafe. Avoid blocking or placing large items near the baffles.
  4. Items placed in or in front of the fume cupboard create air turbulence. This may affect the capture of contaminants, and in some instances gases may escape from the cupboard towards the user. To limit this, ensure that work is conducted in the middle of the bench space, avoiding work and items within 10-15 cm of the front edge or at the back of cupboard obstructing the baffles. (see attached image: Fume cupboard bench layout)

Experiment design

  1. Laboratory personnel are required to design and construct their experiments to minimise hazardous emissions. Fume exhaust emissions (measured at the stack) should be sufficiently diluted or scrubbed to prevent the emission posing a risk to health, safety or the environment. Emissions must be below the mass emissions of the air pollution regulations or the concentration given in occupational exposure standards, or if these do not exist, these emissions should be kept to a practical minimum. With flammable vapours and gases the emissions should be below 10 % of their lower explosive limit.

Additional information on the use of chemicals is available.

See: Chemical Management Policy and Procedure

Operation

  1. Here are some pointers in the correct use of a fume cupboard.

Before use

  • Ensure that the fume cupboard you are using is appropriate. The use of certain biological materials, perchloric acid and perchlorates, large volumes of acids etc. require special features or scrubbing.

See: Table 1 for classification of fume exhaust systems

  • Ensure the fume cupboard is operational and there is an airflow. Listen and feel for air movement - this should be obvious with the sash in its lowest position.

Note: The fan switch for the fume cupboard turns the fan on immediately. However, a fume cupboard goes through a pre-use purge of up to 5 minutes (varies with make and model) before switching on the power to the electrical sockets and gas. Do not start work until this pre-use cycle is complete.

  • Check for obvious surface contamination. Clean if necessary, to avoid adverse reactions with the chemicals in use.
  • Ensure that you have enough space to conduct your work safely.
  • Position equipment, apparatus, and materials in the centre and back of the cupboard to minimise disturbance to airflow. Where practical, place required item within the cupboard before starting operations.

See: Fume cupboard bench layout

Note: Remember that the OHS legislative framework require you to reduce risks and exposure as much as possible. Is it practical to -

  • Reduce the quantities of the substances used?
  • Reduce the amount of substance released into the airflow? eg. use a condenser, watch glass cover bubblers etc.
  • Use a slower reaction rate?

During use

  • Try to avoid sudden rapid movements in front of the cupboard. These can cause turbulence that may draw the airborne hazardous material out of the cupboard.
  • Use the sash position to your advantage -
  • Fully open, to provide access for setting up equipment,
  • Partially open, to a comfortable work height when handling the material inside the cupboard,
  • Lowered as far as is practicable, when the process is in operation and your intervention is no longer required.
  • Any accidental spill of chemicals should be cleaned up as soon as it is safe to do so.
  • If hot plates are used, these should be placed at least 10 cm from the side of the cupboard to avoid damage to the cupboard structure.

After use

  • Dispose of laboratory waste as per the ANU guidelines.
  • Clean and decontaminate the fume cupboard, if necessary.
  • Lower the sash to minimise the waste of tempered air. A fume cupboard should remain on for at least 20 minutes after the process/activity has finished and hot plates have cooled. This is to ensure that all airborne contaminants have been exhausted. Some cupboards may need to be left on, but at their optimal setting.

Note: Modern fume cupboards have a post-use purge cycle, so that once you switch off the fan, the electricity to the sockets and gases are switched off, but the fan continues to run (for up to 20 minutes - varies with make and model).

  • Know what happens when you switch on or off your fume cupboard, and its effect on the power and gases. Ensure that your actions do not adversely effect your experiment or safety.
  • Remember to note maintenance and unusual situations within your fume cupboard log book and discuss with the appropriate person.

Hints

To achieve optimum performance from your fume cupboard ensure:

  • That work is conducted in the middle of the bench space.
  • Minimise the number of items in the fume cupboard.
  • Minimise traffic passing in front of the fume cupboard. Keep a 1m zone in front of the fume cupboard for only the fume cupboard user.
  • Avoid open doors in the vicinity of the fume cupboard.
  • Ensure adequate make-up air into the room.
  • Larger items should be placed further back from the front edge.
  • Do not place storage items between where you are working and the baffle, as this effects air flow.
  • If you are using a radiation shield or blast shield, there is a potential for an air current dead spot to be created. This can be minimised by limiting items to the side of the shield.

Information

Printable version (PDF)
Title Safe use of a fume cupboard
Document Type Guideline
Document Number ANUP_000748
Version 4
Purpose To set out the guidelines for the safe use of fume cupboards.
Audience Staff
Category Administrative
Topic/ SubTopic Health, Safety & Environment - Occupational Health & Safety
 
Effective Date 31 Dec 2007
Review Date 30 Jun 2015
 
Responsible Officer Director, Human Resources
Approved By: Director, Human Resources
Contact Area Human Resources Division
Authority