HEPA Air Filter Construction
Most HEPA air filter units are constructed the same way a continuous length of filter paper is folded back and forth into pleats and corrugated separators are inserted between each fold. The assembly is then sealed into a rigid, open-faced rectangle. The components of a fabricated HEPA filter include:
(1) Extensively pleated filter medium.
(2) Separators that provide air passages and keep adjacent pleats apart.
(3) A rigid filter case that encloses and protects the fragile filter medium.
(4) Sealants used to bond the filter pack (consisting of the assembled pleated medium and separators) to the filter case and to eliminate leak paths between filter pack components.
(5) Gaskets attached to the filter case on one or both open faces to provide an airtight seal between the filter and the mounting frame.
Some filter construction methods form the filter paper on the papermaking machine using an interval means to keep the adjacent folds apart, thereby eliminating a need for corrugated separators. The illustration below shows the assembled components of an open-face, deep pleat HEPA filter with corrugated separators.