Recirculating Clean Bench

What is the Recirculating Clean Bench?

A recirculating clean bench returns filtered air to the work zone instead of exhausting it, so no duct is needed. It suits clean, non-hazardous work in temperature-controlled rooms and low-humidity laboratory spaces.

Overview

Most air passes the HEPA filter and returns to the work zone, with a small make-up and bleed exchange with the room. This keeps a clean work surface and avoids a duct, reducing heating, cooling and humidity loads, which is valuable in temperature-controlled or low-humidity rooms. Because captured particles stay on the filter, recirculation is limited to work that releases no hazardous aerosol, vapour or excessive dust, since HEPA filters do not remove gases. Supply is HEPA H14 at 0.3–0.5 m/s in the chosen direction, and a pressure gauge and airflow alarm are fitted. The bench is requalified like a ducted unit, and the make-up and bleed must be arranged so the room and bench stay in balance.

How does it work?

A clean bench supplies filtered air in one direction across an open work surface, so particles generated by the work or carried in the room are swept away from the sample. Room air passes a prefilter and then a HEPA filter rated at least 99.97 % efficient at 0.3 µm, or a ULPA filter at 99.999 %, and a diffuser makes the stream uniform at 0.3–0.5 m/s. Horizontal designs flow from the back of the bench to the front, while vertical designs descend from the top. The open front gives good access but no operator protection, so clean benches are used only for work that produces no hazardous aerosol or chemical vapour. The work zone can reach ISO 5 in a suitable room. Filter loading is shown by pressure, and airflow and filter integrity must be verified, because draughts and obstructions disturb the laminar stream.

What are the key features?

• Most air recirculated through the HEPA filter
• Small make-up and bleed with the room
• No duct required
• HEPA H14 supply 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 clean bench configuration offers flow direction of Horizontal or vertical, 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 Clean Bench is used in temperature-controlled assembly, optical and electronic work, clean inspection without ducting and small-part packaging. Across the wider Clean Benches class, laboratories also deploy it for aseptic assembly and inspection, media preparation and plating and electronics and optics work.

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 bench away from doors, air diffusers and traffic, because draughts above about 0.2 m/s break the laminar stream. Verify filter integrity and face velocity at installation and at least annually, changing prefilters every 3–6 months. Keep the work surface free of large items, place objects to the side rather than in front of the filter face, and do not block the air exit. Clean with compatible agents, and avoid aerosols that would load the filter. Never use a clean bench for hazardous aerosols or volatile chemicals, since the open front offers no protection. Record requalification and filter changes, and confirm that the recirculated or ducted exhaust suits the room and any local rules.

How do I select the right Recirculating Clean Bench?

Choose recirculation where no duct is available and the work 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 Clean Benches variants?

Choose the flow direction first: horizontal for flat work needing clear access, vertical for tall items and where downward flow is preferred. Then decide the exhaust arrangement: ducted where exhaust must leave the room, recirculating where no duct is available and the work is clean. Select the construction: powder-coated steel for general use, and stainless steel for aseptic, GMP or high-humidity environments with cleanable surfaces and documentation. Choose filter class for the cleanliness target, HEPA H14 for ISO 5 and ULPA for ISO 4 or better, and match width and working height to the equipment. Confirm the bench does not need to protect the operator, and if it does, specify a biosafety cabinet or fume hood instead. Verify face velocity, filter integrity and particle counts at commissioning, and plan requalification.