Recommendations for Placing LAF Cabinets

A safety cabinet is only as safe as its usage and its placement in the laboratory.

Many factors are important if maximum safety is to be achieved when working in an LAF cabinet.

• Room height
• Ventilation
• “Traffic”
• Other equipment in close proximity
• Use of certified cabinets to ensure the cabinet has the right product features.

The placement of the cabinet and its position in the laboratory can significantly affect its performance, as it can be strongly influenced by other equipment, such as walls, tables, laboratory traffic, and of course the room’s air systems. Relevant guidelines, for example, BS 5726:2005 from the UK, provide advisory information on cabinet placement. Following these guidelines will ensure that the cabinet provides maximum protection for both person and product. A safety cabinet is only as safe as its usage – and likewise only as safe as its placement in the laboratory.

Room Height
The height of the room from floor to ceiling, where the cabinet is to be placed, must also be considered, especially if the cabinet is to be placed on a height-adjustable stand rather than a fixed-height stand. It is essential to accurately measure the area and consider any ceiling-mounted lamps or other installations that might be affected by the installation.

If the cabinets are to recirculate exhaust air back into the laboratory, there should be a clearance of about 20 cm above the cabinet. This ensures that the exhaust air does not encounter obstacles that could affect the air flow pattern in the cabinet, and also ensures unobstructed access for service, including periodic tests of the exhaust filter.

If cabinets are to be installed against a wall, it is recommended to leave a bit of space behind them so as not to disturb the exhaust air. A distance of about 5 cm from the back wall is ideal, especially if the cabinets are placed side by side, or if other equipment such as incubators or refrigerators is located nearby.

In Denmark, cabinets are typically connected to external ventilation, and therefore the room height should ideally be about 270 cm to accommodate an optimal seating position at the cabinet. When using height-adjustable stands, it is recommended to place the cabinet about 5 cm from the back wall, and to avoid a pinching risk, there should be at least 2.5 cm distance to the nearest other installation.

Ventilation and Air Conditioning When designing a new facility, great care must be taken not only with the cabinet’s placement in relation to surrounding traffic and equipment but also with the placement of air conditioning intakes and exhaust fans.

Make-up Air
In Denmark, most safety cabinets are connected with fixed and tight exhaust over the cabinet's exhaust. In these cases, there will be a need to supply make-up air to the room. This make-up air is supplied via air ducts or ceiling diffusers of various designs. The placement of these should be carefully considered, as they can make the flow diffuse and cause turbulence past the cabinet's front window. Ceiling-mounted diffuser grilles should ideally be adjustable, so they can direct air away from the cabinets if necessary. Common “swirl” type diffusers should never be used, as they create a high level of turbulence, which can negatively affect the safety cabinet's flow pattern. It is recommended that air velocities in the room should be kept below 0.3 m/sec. There is limited information available on how far the cabinet should be from air intakes.

Laboratory Traffic
A crucial condition for optimal cabinet performance is its correct placement in relation to the traffic in the area around the cabinet.

Testing the Installation
The safest method is to perform a smoke test to visualize the airflow or to perform a Kl-discus test at the installation to ensure the cabinet's flow pattern is not disturbed. Distances of at least 1.5 meters diagonally from the AC unit should be considered as a minimum, but even this may be too little if the airflow is strong.