Recirculating Horizontal Laminar Flow Cabinet

What is the Recirculating Horizontal Laminar Flow Cabinet?

A recirculating horizontal laminar flow cabinet returns filtered air to the work zone instead of exhausting it, preserving room conditions. It suits enclosed clean processes where ducting is impractical and energy saving is valuable.

Overview

In this design most air is recirculated through the HEPA filter and returned to the work zone, with only a small make-up and bleed flow exchanged with the room. This keeps the work zone clean, reduces heating and cooling load, and avoids a duct. Because contaminants captured on the filter are not exhausted, recirculation is limited to work that produces no hazardous aerosol, vapour or excessive dust, since the HEPA filter cannot remove gases. A small amount of air is usually bled to the room to balance the system. Supply is HEPA H14 at 0.3–0.5 m/s across the bench. The cabinet suits electronic assembly, optical work and clean inspection, and works well in temperature-controlled rooms where exhausting large air volumes would disturb conditions.

How does it work?

In a horizontal laminar flow cabinet, room air is drawn through a prefilter and a HEPA filter and then pushed through a rear plenum and diffuser. It leaves the back grille as a unidirectional stream at 0.3–0.5 m/s and crosses the entire work surface before reaching the operator, carrying particles and microbes away from the work. Because the stream comes from behind the work, the operator has clear access to the whole bench with no barrier or downward draught. Air may then exhaust to the room or be ducted or recirculated depending on the model. The filter removes at least 99.97 % of 0.3 µm particles for HEPA and 99.999 % for ULPA. Face velocity, filter integrity and particle counts are the performance measures, and the laminar stream is easily disturbed by draughts, so the cabinet must be sited away from doors and air supply diffusers.

What are the key features?

• Most air recirculated through the HEPA filter
• Small make-up and bleed exchange with room
• No duct required
• Reduced heating and cooling load
• HEPA H14 supply at 0.3–0.5 m/s
• Limited to non-hazardous, non-gaseous work

What are the technical specifications?

A typical recirculating horizontal laminar flow cabinet configuration offers flow direction of Horizontal, rear to front, filter class of HEPA H14, ≥ 99.97 % at 0.3 µm, face 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 Horizontal Laminar Flow Cabinet is used in temperature-controlled assembly, optical and electronic work, cleanroom inspection without ducting and small-part packaging. Across the wider Horizontal Laminar Flow class, laboratories also deploy it for electronics and optics assembly, media preparation and plating and inspection and packaging.

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, windows, air diffusers and walkways, since draughts above 0.2 m/s disturb the horizontal stream. Verify filter integrity and face velocity at installation and at least annually, changing prefilters every 3–6 months. Keep the work area clear of large objects that block the stream, and place items at the sides rather than directly in front of the filter face. Clean the work surface and interior with compatible agents and avoid aerosols that could contaminate the filter. Do not use the cabinet for hazardous aerosols or chemical vapour, since it protects only the work. Record requalification results to support audits.

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

Choose recirculation when the room cannot take a duct and the work produces no hazardous gas or heavy dust. Confirm the bleed and make-up arrangement keeps the room balanced. RFQ: width, work type, room conditions, cleanliness target and airflow.

How does it compare with other Horizontal Laminar Flow variants?

Choose a horizontal laminar flow cabinet when the task needs clear, unobstructed access to the work surface and the operator does not need protection from aerosols. Decide whether the cabinet recirculates, exhausts to the room or is ducted, based on room conditions and the process. Select filter class by the required cleanliness, commonly HEPA H14 for ISO 5 and ULPA for ISO 4 or better, and match width and working height to the equipment. For GMP or aseptic use, choose stainless steel construction with cleanable surfaces. Confirm face velocity, filter integrity and particle counts at commissioning, and check that the site has no strong draughts. Horizontal flow is less suitable for tall work or when the operator must lean over the work, since the air then travels towards the operator's breathing zone.