RECIRCULATED FUME CABINETS
Recirculating Fume Cabinets have been developed to protect laboratory staff and the environment from toxic vapours, gases, fumes and particles. Cabinets are designed to comply with the Australian Standard AS2243., Recirculating Fume Cabinets.

N.B. - Specifiers and intending users should see AS2243.9, Clause 1.2 that sets out the intended applications and limitations of these cabinets.

FIXED FUME CUPBOARDS AND THEIR LIMITATIONS
Ducted fume cupboards, as described in AS2243.8, are permanently installed, fixed work stations that maintain an inward flow of room air to contain aerosols produced in the handling of hazardous chemicals. A typical fume cupboard exhausts from the room an air quantity of approximately 500 litres/sec. This is an amount that is much greater than that typically supplied by the air conditioning system to a small room.

So, unless the building air handling system is designed to supply an air quantity to balance such an exhaust volume, or a make-up air system is installed, installation of a fume cupboard may not be possible. The complication and cost of upgrading an air handling system to accommodate the airflow of even one (1) fume cupboard may be prohibitive. As these enclosures are fixed, their use at sites where fume-generating materials are handled at multiple locations is limited.

RECIRCULATING FUME CABINETS DESCRIPTION
Recirculating Fume Cabinets can be installed on a standard laboratory bench, or on an optional floor stand or trolley. Cabinets have similar inward airflow to ducted units. Inward air velocity is maintained at >0.5 m/s ± 20%. In most applications, filtered exhaust air may be discharged to the room. This avoids the air supply system problems that arise with ducted cabinets. In special cases, where the nature or concentration of the contaminant indicates the cabinet exhaust may be connected to an exhaust fan/duct system that discharges to atmosphere. Recirculating Fume Cabinets are manufactured to customer requirements.

Air exhausted from the top of the cabinet is filtered by a two-stage filtration system. A pre-filter protects the final filter system from particulates >5µm. The final activated carbon filter incorporates carbon granules with a selected chemical impregnation to optimise the arrestance of specific vapours. Specific impregnations are available for the handling of a wide range of contaminants.

The contaminants include:

• Formaldehyde and Glutaraldehyde
• Ammonia and Amines
• H2S and Mercaptans
• Alkaline Odours
• Inorganic acids and acidic odours
• HCN

Basic cabinets are designed for bench top use. An optional PVC work tray is required for most applications. When supplied without the work tray, the cabinet may be installed over a sink or an item of equipment. RFC cabinets can be supplied with a special trolley or stand which allows a separate trolley to be wheeled into the containment enclosure. The mobility of trolley mounted RFC cabinets is a significant advantage in hospitals or large research institutions, where materials such as glutaraldehyde are handled at multiple locations. These applications include endoscope sterilisation.

CONSTRUCTION

Cabinet
Fully constructed in chemical resistant/flame retardant UPVC sheet.

Fan
A direct drive motor/blower is regulated by a variable speed controller to enable airflows to be maintained through filter life.

Activated Carbon Filters

Special absorption filters developed for the capture of a wide range of vapours.
Filters employ coconut shell carbons with a highly developed internal surface area and with a non-crystalline structure produced by controlled oxidation of coconut shells. The cellulosic structure determines the efficiency of the absorptive media. Chemical impregnation of the carbon produces a chemical reaction similar to an oxidation process when the contaminant is absorbed. This process extends filter life, as the surface of the catalyst will not be covered by molecules trapped on it, thus enabling the process to be repeated.

These filters will operate effectively in environments with temperature up to 70ºC, and with relative humidity up to 80%.

Pre-filters
An easily accessed, washable polyester pre-filter arrests not less than 90% of particulates >5µm, thus prolonging carbon filter life. A warning light in the control panel signals the need for pre-filter service.

Electrical
Cabinets operate on single-phase 240V, 50Hz power via a 10A outlet. A low voltage touch control panel with function status indicated by LEDs is located on the front of the cabinet. Glare-free fluorescent lamps provide a minimum lighting intensity of 800 lux at the work surface.

MANUFACTURING AND TESTING
Computer-aided design and manufacturing ensures that design and quality standards are maintained in production. Each cabinet is factory-tested and certified by a NATA-registered laboratory to establish compliance with the performance requirements of AS2243.9.

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