Ducted Clean Bench

What is the Ducted Clean Bench?

A ducted clean bench exhausts its air to atmosphere instead of returning it to the room. It is chosen where exhaust must leave the room or where recirculation is not permitted by local rules.

Overview

The bench supplies HEPA-filtered air across the work surface at 0.3–0.5 m/s, and the air leaving the work zone is carried outdoors by a duct rather than recirculated. The exhaust duct must be sized for the bench airflow, and because supply and exhaust interact, a volume control or fan speed adjustment keeps face velocity in range when building exhaust pressure varies. The enclosure is usually stainless steel with a smooth interior, and a pressure gauge shows filter loading. Removing the exhaust suits work that produces fine dust, such as powder handling, or odorous processes, and rooms where air cannot be returned. An airflow alarm warns of loss of flow, and the exhaust fan is normally dedicated to the bench.

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?

• Ducted exhaust of air from the work zone
• HEPA supply at 0.3–0.5 m/s
• Volume control to protect face velocity
• Stainless steel, smooth cleanable interior
• Suited to dusty or odorous work
• Airflow alarm and filter pressure gauge

What are the technical specifications?

A typical ducted 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, exhaust of Ducted to atmosphere, duct diameter of 200–300 mm and airflow of 400–1200 m3/h. 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 Ducted Clean Bench is used in powder and fine-dust handling, odorous or abrasive processes, rooms where recirculation is prohibited and cleanroom exhaust applications. 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 Ducted Clean Bench?

Choose ducted exhaust when air must leave the room, for example with fine dust or where rules prohibit recirculation. Confirm duct sizing and that building exhaust does not alter face velocity. RFQ: airflow, duct route and diameter, fan details and width.

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.