Particulate air filter assembly

A high efficiency particulate air filter assembly having low air flow resistance, said filter assembly comprising:

• an annular filter element having a diameter in the range of 3.0 to 5.0 inches, the filter element being formed from a relatively thin filter media folded to provide a number of circumferentially spaced pleats, the fold lines of which extend radially relative to the axis of the filter element, the inner edges of the pleats being bonded together to define a central opening therein, the pleats having a height from 0.4 to 1.1 inches, and the number (N) of pleats being in the range, said range being defined by ##EQU3## where "d" is a numerical value equal to the diameter in inches, and "h" is a numerical value equal to the pleat height in inches;
• closure means closing the central opening;
• a canister shell of generally cup-shaped configuration having an apertured end face, an open end, and a generally cylindrical portion disposed between the end face and the open end, the filter element being received within said canister shell and having the outer edges of the pleats bonded to the inner wall surface of the cylindrical portion;
• and
• an apertured cover, the peripheral edge of the cover being interconnected to said shell adjacent said open end whereby the filter element is enclosed within said canister shell.