Recirculating Vertical Laminar Flow Cabinet

What is the Recirculating Vertical Laminar Flow Cabinet?

A recirculating vertical laminar flow cabinet returns filtered air to the work zone, avoiding a duct while maintaining downward product protection. It suits enclosed clean processes in controlled rooms and temperature-controlled areas.

Overview

This design recirculates most of the HEPA-filtered air through the top plenum and back over the work zone, with a small make-up and bleed exchange with the room. The downward stream descends at 0.3–0.5 m/s and keeps particles from settling on the work. No duct is required, which reduces heating and cooling demand and suits temperature-controlled or low-humidity rooms. Because captured contaminants remain on the filter, recirculation is limited to work that releases no hazardous aerosol, vapour or excessive dust, since HEPA filters do not remove gases. A pressure gauge and airflow alarm are provided, and the cabinet is requalified like a ducted unit. It is common in electronics, optics and small-part assembly where the process is clean but demanding.

How does it work?

In a vertical laminar flow cabinet, room air is drawn through a prefilter and a HEPA filter located at the top, and a plenum and diffuser distribute it as a unidirectional stream that descends at 0.3–0.5 m/s over the work zone. Particles shed by the work are swept downward and away rather than towards the operator, and because the flow is vertical, taller items disturb it less than in a horizontal cabinet. Air leaves at the front of the work area and may be exhausted to the room or ducted, and some models recirculate most of the air. The supply filter removes at least 99.97 % of 0.3 µm particles for HEPA and 99.999 % for ULPA, giving ISO 5 or better at the work surface. Face velocity, filter integrity and particle counts are verified, and the cabinet must be sited away from draughts that could break the laminar stream.

What are the key features?

• Most air recirculated through top HEPA filter
• Small make-up and bleed with the room
• No duct required
• Vertical downflow at 0.3–0.5 m/s
• Reduced heating and cooling load
• Limited to non-hazardous, non-gaseous work

What are the technical specifications?

A typical recirculating vertical laminar flow cabinet configuration offers flow direction of Vertical, top to work surface, filter class of HEPA H14, ≥ 99.97 % at 0.3 µm, downflow velocity of 0.3–0.5 m/s, recirculation of ≈ 90 % with bleed, exhaust of None, room make-up and bleed and width of 900–1800 mm. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Recirculating Vertical Laminar Flow Cabinet is used in temperature-controlled assembly, optical and electronic work, cleanroom inspection without ducting and small-part packaging. Across the wider Vertical Laminar Flow class, laboratories also deploy it for cell culture and sterile handling, electronics and semiconductor assembly and media preparation and plating.

Which standards and certifications apply?

Relevant standards and methods include ISO 14644-1 (cleanroom classification), ISO 14644-3 (test methods), IEST-RP-CC002 (unidirectional flow clean-air devices), EN 1822 (HEPA and ULPA filters), EU GMP Annex 1 (sterile manufacturing) and GB 50073 (cleanroom design code). Certification candidates for this model are CE and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Site the cabinet away from doors, air diffusers and people traffic, since draughts above about 0.2 m/s disturb the downward stream. Verify filter integrity and face velocity at installation and at least annually, and change prefilters every 3–6 months. Place tall items so they do not block the diffuser, and keep the front opening clear so air can exit. Clean surfaces with compatible agents and avoid generating aerosols that load the filter. The cabinet protects the work rather than the operator, so do not use it for hazardous aerosols or chemical vapour. Record requalification results, and confirm the recirculated or ducted exhaust path meets room requirements.

How do I select the right Recirculating Vertical Laminar Flow Cabinet?

Choose recirculation when no duct is available and the process releases no hazardous gas or heavy dust. Confirm make-up and bleed keep the room balanced. RFQ: width, work type, room conditions, cleanliness target and airflow required.

How does it compare with other Vertical Laminar Flow variants?

Choose vertical laminar flow when the work is tall, when the cabinet contains a central obstruction such as a jig, or when downward flow is preferred so that particles do not travel towards the operator. Decide whether the cabinet recirculates, exhausts to the room or is ducted, and select HEPA H14 for ISO 5 or ULPA for ISO 4 or better. Match internal height and working depth to the equipment, and consider a sash or partial front for increased operator comfort. For regulated or aseptic work, choose stainless steel with cleanable surfaces and documentation. Confirm face velocity and cleanliness at commissioning. Vertical designs are often preferred in cell culture and sterile handling where a downward draught over open vessels reduces contamination from above.