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Background

The Australia/New Zealand standard safety in Laboratories; Fume Cupboards - 2006 is the latest edition of the four edition published of Standards Australia and Standards New Zealand. It is the 8th standard and included in the 10 part standard "Safety in Laboratories" The standard was prepared by Joint technical committee CH-026, safety in laboratories, and was approved on behalf of the council of standards Australia and New Zealand. It was made to ensure that employees, employers and students are familiar with safe practices within laboratories and also requirements on how the workplace is set up and buil e.g. positioning of the fume cupboard within the room.

Changes from previous standard:

The 2006 edition of the standard acknowledges clarify the operations of the fume cupboard. For example, double-sided fume cupboards now require for one of the two sides to be closed during operation. In the previous edition, recommendation were made regarding distances between the positioning of the fume cupboards from other objects such as other work related benches have now been updated as requirements to minimise and prevent containment problems. Other updates include:

• Fire isolation of exhaust ducts
• The use of exhaust filters and it’s test methods
• Clarifying requirements regarding the use of isolators.

Section 1

Scope of this Standard

Section one “scope and general” provides an introduction to how the standard can be used, such as providing an outline of appendix A in how it introduces the methodology for conducting a smoke test for a fume cupboard. It also further outlines that there are no specific standards to recirculating fume cupboards which is actually included within another standard “AS/NZS 2243.9”

Section 1 of the standard also includes a list of reference to other standard that provide useful information for employees and employers to research on in regards to the standard itself, and a glossary of terms.

Section 2

Fume Cupboard Types

Fume cupboards can be divided into 3 major groups, bench type cupboards, recirculating fume cabinets and walk-in fume cupboards.
Recirculating fume cupboards are mainly used for educational facilities or where laboratory design does not allow for external ducting. This type of fume cupboard is typically fitted with a fan either on top of the hood, or under the work area. Air is drawn through the front opening of the cabinet, filtered and passed back into the laboratory environment.
Walk-in fume cupboards are designed for larger scale work, accomodating tall test assemblies and providing a high headroom in full hazard protection and containment environments.
Bench fume cupboards are the most common type, used most laboratories. Bench fume cupboards can be further divided into 5 sub-groups:

1. General Bench Fume Cupboard
2. Downdraught Fume Cupboard
3. Variable Air Exhaust Volume Fume Cupboard
4. By-Pass Fume Cupboard
5. Double-Sided Fume Cupboard

Servicing

All electrical services required for the operation of a fume cupboard, including piping, the exhaust, control and lighting systems must be in accordance with Australian/New Zealand standards (AS/NZS 3000). Examples from AS/NZS 3000: Electrical service outlets should not be positioned within the fume cupboard as they are an ignition hazard. All controls must be accessible to fume cupboard operators and located on the outer surface of the fume cupboard or on the supporting structure. An autmoatic emergecy isolater must be fitted, in case of mains power failure, low face velocity intake or similar emergencies. A room emergency switch must not interrupt the power supply to the exhaust system. The fume cupboard must be fitted with audible and visual fault indicators which operate in an equivalent manner to the emergency isolators in case of low air flow or power failure.

• Bulleted list item

Section 3

Airflow Requirements into Fume Cupboard

The fume cupboard should be free of turbulence, sucking air away from the operator and working chamber without allowing fumes to be sucked out by eddy currents inside or outside the cupboard. This can be achieved by correct design, use of aerofoils and baffles. A fume cupboard must maintain a minimum airflow of 5 cupboard volumes per minute during operation Face velocities should not be less than 0.5 m/s (in relation to measurements according to Appendix B), but should not exceed 1m/s. Air distribution systems diffuse air into the laboratory at low velocity, far away from any fume cupboards, toward the cupboards. The net volume of air supplied should be slightly less than the volume of air removed (~10%) to maintain a negative pressure in the laboratory and to insure the airflow through the cupboard is dependent on the cupboards exhaust system. #Air conditioning systems should comply with standards to minimise turbulent airflow caused by them. Containment of fumes can be altered by:

1. Varying face velocity (limited due to turbulence inside/outside the cupboard and energy consumption)
2. Using well-designed baffles
3. Minimising eddies in the cupboard (by using aerofoils and aerodynamic leading edges)
4. Reducing turbulence inside and outside the cupboard and cross-draughts
5. Reducing size of aperture opened when working.

Fume Exhaust and Dispersal

The exhaust system is designed to contain and move potentially dangerous fumes from the cupboard to a safe storage point so that they may be safely disposed of. A negative pressure is maintained in the exhaust system to prevent leaking hazards. To prevent potentially dangerous reactions taking place, exhaust from each fume cupboard should be stored individually. A fan should be selected to maximise efficiency and stability of a desirable range of airflows. The fan should also be physically and chemically resistant to temperature and potential fumes and fitted so that it can be cleaned and maintained, labelled appropriately to indicate special safety requirements for staff and should have a drain for disposal of cleaning agents. All ductwork (including gaskets and joins) must:

1. Be chemically resistant, smooth and non absorbent.
2. Follow the straightest path possible to drainage point and have maximum radii practicable at curves, avoid horizontal ducts and be fitted with drainage points at all low sections of the ducts
3. Accommodate thermal expansion/contraction and be leak proof and fire proofed.

Experiments should be designed to control and minimise the amount of fumes being discharged into the system. These fumes should not exceed contaminant levels specified by the appropriate regulation authority. Fume discharge should have a minimum velocity of 10m/s and be discharged vertically upwards, located far away from air intakes and with respect to obnoxious exhaust and electrical requirements for hazardous areas.

Section 4

Fume Cupboard Location

The location of the fume cupboard is important and must be accounted for in the design of new laboratories and the modification of existing laboratories. Installation of fume cupboards must comply with Australian Standads, including National, State and Territory requirements for general environmental safety and operator comfort. For each fume hood installation, the site must be assessed individually to take account of risks involved with the operation of a fume hood and nearby hazards. The location assessment must take into consideration:

1. The height of the working surface
2. Nearby airflow disturbances
3. Escape routes in case of fire or explosion in the fume hood

Once installation is completed or a fume hood has major changes applied to it, the system must be tested for overall compliance with Australian Standards and all applicable environmental standards. The fume cupboard tester must be qualified to undertake this task. The completed report should be submitted to the laboratory manager of the laboratory containing the fume cupbard. The results of all commissioning tests are recorded and copies retained within the operating and maintenance manuals.

Section 5

Fume Cupboard Maintenance and Testing

There are three periodic maintenance procedures that need to be performed on fume cupboards:

Frequent Inspection

Fume cupboards should be inspected a minimum of once each week, particularly the air filtering devices. All particles and substances found should be cleaned off.

Bi-Yearly Testing

Every six months a face velocity and smoke test should be performed. All exhaust systems should also be tested and maintained. If there is a scrubber and wash-down facility fitted, it should also be checked and maintained.

Annual Inspection

Similar to the Bi-Yearly testing, however the annual inspection requires a complete top-bottom inspection and maintenance of the fume cupboard.

Section 6

Fume Cupboard Usage Risk Assessment

Use of liquids in the fume cupboard: Consideration that must be taken into account when using liquids in the fumecupboard:

1. The type of liquids being used
2. The volumes of each type of liquid being used;
3. The pressure and temperature of each liquid during use;
4. The likelihood of a spill
5. The potential of reaction between spills and other chemicals in the fume cupboard
6. The risk to an operator if a spill is not contained within the fume cupboard.

Use of flammable liquids: If there are flammable liquids involved the following consideration should be taken into account:

1. Physicochemical properties such as flashpoint, volatility and boiling point;
2. Processing methods being used, e.g. heating, mixing methods which cause aerosols or increase vapour, distillation or evaporation
3. Risk of spreading flames/fire if a container or spill ignites

Fume Cupboard Management

Before Usage

Before usage, a fume cupboard must be checked that it is suitable for planned usage. Wash-down facilities must be checked to ensure working condition. Fume cupboard must be inspected to be free of dangerous contamination.
Position apparatus and materials toward the center and back of the cupboard to minimize airflow disturbance at the working aperture.
Ensure suitable fire extinguisher(s) are on-hand, especially when using flammable substances.

During Usage

Use only the following sash positions:

1. Fully open to provide adequate access when setting up apparatus, performing processes or adding reagents
2. Partially open when handling chemicals inside the cupboard
3. Lowered as far as practical when not required to be open

Also, while in use, use the minimum required quantity of chemicals necessary and where possible, use reaction rates that minimize hazards (e.g. overly-vigorous evolution of fumes).
Use appropriate protective equipment.

After Usage

After use dispose of laboratory waste in accordance with safe laboratory procedures and relevant regulations. Lower the sash enough to minimize the effect of outside disturbances while allowing satisfactory airflow. Ensure that the fume cupboard is clean and free from contaminants and that all stock chemicals are replaced from the fume cupboard to appropriate storage.

Appendix A

Conducting a Smoke Test

A fume cupboard smoke test provides visual evidence of fume containment or escape from the fume chamber. It is a part of the Bi-Yearly testing. The Smoke used to assess fume cupboard performance shall be generated using air current tubes. A fume cupboard shall be assessed according to its worst score.

Appendix B

Determining Face Velocity

Air flow face velocity test should be performed periodically every six months and should be done after the smoke test. The readings are measured at the sash opening of the fume cupboard using an anemometer at a series of equally spaced points to determine the uniformity and stability of the airflow.

Appendix C

Materials of Construction

The materials chosen for the construction of a fume cupboard are of great importance. The materials making up the fume cupboard shall be selected to satisfy the nature of chemicals to which materials are to be exposed and the requirements of the user. The following is a list of the most used materials for fume cupboard construction with relevant requirements and warnings concerning their use:

Material	Requirements	Warnings
Stainless Steel	Grounded for Electrical safety	Choose carefully as some commonly used acids attack some grades of stainless steel readily. (In particular, perchloric acid, which must be washed away immediately)
Plastics	Before using any polymer the polymer manufacturer should be consulted as to which grade is the most suitable for intended usage	Plastics can present a fire hazard, owing to their flammability and loss of strength at high temperatures
Glass	Special precautions must be taken when using glass with hydrofluoric acid	Glass may be hazardous when broken, this can be avoided by using special glasses, for example Tempered Glass, or using plastic films to protect it
Timber	Heat sources capable of operation over 100 degrees Celsius should not be used in timber fume cupboards	Timber fume cupboards are absorbent and may present a hazard by absorbing fumes and vapours into the structure

Appendix D

Construction

The design of a fume hood should incorporate several features that are key to keeping the fume hood functional with a variety of chemicals / chemical reactions. These features include:

1. Smooth, non absorbent surfaces.
2. Chemically inert materials.
3. Rounded corners.
4. Thermal stability.
5. Combustibility.

General purpose fume hoods will be used to handle a large range of substance. Special consideration should be made for some chemicals. E.g. In case radioactive substances will be handled, the fume hoods frame should be able to withstand the weight of lead utensils. Perchloric acid creates shock sensitive and explosive perchlorates with some metals and organic substrates. To accommodate such a reactive species there should be special emphasis on chemically inert and smooth materials in the construction of the fume hood. Hydrofluoric acid contaminates skin and etches glass/ceramics. Calcium gluconate gel and safety labels should be easily accessible. Further consideration is required for the ducts and motor system, in particular:

1. Dust and condensate should be washed from the cupboard and surrounding ducts (minimise unwanted reactions)
2. Duct fan should be acid resistant and outside the laboratory. Should also be powered by external motor.
3. Fan housing should have a drain (to drain water from washing the system).

Appendix E

Procurement

Before a fume hood is procured, a risk assessment should be performed to take into account

1. Chemicals that will be handled
2. Conditions fume hood will be used under (i.e. temperature range, frequency of usage)
3. Required volume inside the fume hood

The risk assessment should also include all safety information, supplementary equipment to be used and physical specifications of the hood. Connection requirements and maintenance information must be considered when procuring a fume hood. The fume hood procurer should state, in writing, all site conditions (i.e. local hazards, policy matters) as part of a contract. Contract work period and terms of fume hood acceptance, including liability and maintenance details should be specified as part of the tender. All parties relevant to the tenders should be aware of all applicable OH&S requirements and pollution/effluent disposal requirements.

See Also

Duct Fume Cupboard

References

Lab Conco
University of Waterloo, Canada
RHM Consultants