Two-stage air filter with multiple-layer stage and post-filter stage

An air circulation system comprising:

• a fan coupled to air stream ducting of the air circulation system for causing movement of air in a stream through the ducting;
• a filter holder for an air filtering device supported within the air stream;
• and
• an air filtering device having at least a first filter element and a second filter element, at least one of the first and second filter elements being of pleated configuration, wherein:
• the first filter element includes at least one layer of a first filtering material, at least one layer of a second filtering material different from the first filtering material, a support member interposed between and secured to the first layer and the second layer, and activated charcoal disposed within at least one of the layers;
• the second filter element is constructed of a filtering material which includes at least one of glass fibers and potassium permanganate;
• and
• the at least one pleated filter element includes pleat support members.

An air filter for use in an air circulation system, comprising:

• a housing configured to hold filter elements, the housing including a peripherally disposed enclosing member, an inlet screen member, and an outlet screen member;
• a first filter element configured to remove particles from the air which are at least as large as a first size, the first filter element including activated charcoal;
• a second filter element configured to remove particles from the air which are of second sizes, the second sizes being smaller than the first size, the second filter element including at least one of glass fibers and potassium permanganate;
• and
• a reticular support member interposed between and substantially in contact with the first filter element and the second filter element.

An air filter for use in an air circulation system, comprising:

• a housing configured to hold filter elements, the housing including a peripherally disposed enclosing member, an inlet screen member, and an outlet screen member;
• a first filter element having at least one layer of a first filtering material, at least one layer of a second filtering material different from the first filtering material, and a reticular support member which is interposed therebetween and is secured to the at least one layer of the first filtering material and to the at least one layer of the second filtering material, the support member including a plurality of openings therein, the first filter element configured to include pleats and to remove particles from the air of at least a first size;
• and
• a second filter element configured to include pleats and to remove particles from the air which are of second sizes, the second sizes being smaller than the first size.