Presenting a rapid, dry method for measuring particulate contamination on surfaces

In cleanrooms and controlled environments, the most popular method for monitoring particulate contamination is the aerosol particle counter. But this method is only effective for particles ≤ 5μm because larger particles tend to settle very quickly. Both dry and wet methods for measuring particle contamination on surfaces exist. However, only dry methods are appropriate for the extremely large surfaces common in industrial applications. This paper introduces a novel measuring system capable of counting and sizing particles (⪆2μm) µm on critical surfaces. Based on the principle of oblique- or glancing-side-light with image processing, this technique is fast (~10 seconds), and does not require extensive capital investment in equipment and in personnel training. We will present results showing that surfaces of interest can be measured directly once appropriate instrument settings have been developed for each surface, a process that will also be discussed in detail in the work. This paper will also demonstrate that particles of interest can sampled from surfaces by means of a tape lift system that ensures a consistent, zero-particle background for each test that is independent of surface geometry. The reliability and robustness of the data is shown. The system facilitates and supports the contamination control in accordance with international standards such as ECSS, IEST-STD-1246, ISO 14644, ISO 16322.