The clean bench (Clean Bench, CB) is designed to meet the cleanliness requirements for localized work areas in modern industry, the optoelectronics industry, biopharmaceuticals, scientific research, and other fields. The clean bench (CB) differs from the biosafety cabinet: a clean bench only protects the reagents and other materials handled inside it from contamination and does not protect the operator, whereas a biosafety cabinet is a negative-pressure system that effectively protects the operator.

Its working principle is: a fan draws air into a pre-filter; the air then passes through a plenum box into the HEPA filter, and the filtered air is delivered as a vertical or horizontal airflow, bringing the work zone to Class 100 cleanliness and ensuring that production meets environmental cleanliness requirements. Clean benches are divided by airflow direction into vertical-flow clean benches (Vertical Flow Clean Bench, VFCB) and horizontal-flow clean benches (Horizontal Flow Clean Bench, HFCB). In a vertical-flow bench the fan is at the top, so the noise is greater, but the vertically blowing air is mostly used in pharmaceutical engineering, protecting human health; the horizontal-flow bench is quieter, with air blowing outward, so it is mostly used in the electronics industry and has little impact on health. By operating structure, clean benches come in single-sided and double-sided operating versions, and by purpose they can be divided into ordinary clean benches and biological (pharmaceutical) clean benches.

By airflow direction, clean benches are divided into vertical-flow and horizontal-flow types; by number of operators, into single-person and double-person benches; and by structure, into conventional, new sliding-sash, and self-circulating types (vertical flow only).

Features of clean benches:

  1. Electrostatic powder-coated surfaces; a quasi-enclosed integral stainless-steel worktop that effectively prevents external airflow from entering and prevents operating odors from irritating the operator.

  2. An adjustable-air-volume fan system with a soft-touch switch and two-speed voltage regulation ensures that the work-zone air velocity is always in the ideal state.

  3. The soft-touch switch adjusts the air volume, ensuring that the work-zone air velocity stays within the required range.

[Figure: Fig. 7-38 Clean benches (left: vertical-flow clean bench; right: photograph of a horizontal-flow clean bench)]