A system for filtering an airflow of exterior ambient air. The system includes a plurality of frame uprights, a plurality of crossbars pivotally connected to the frame uprights and a plurality of filters that are slidably received between the plurality of crossbars.

The present disclosure generally relates to air filters expandable from a collapsed arrangement to an expanded, end-use arrangement and to methods of making, using, and installing such air filters. Some embodiments relate to an air filter having an expanded state and a collapsed state. The air filter includes a filter media assembly including (1) filter media including a plurality of pleats, (2) first and second opposing sides, and (3) first and second opposing ends. The air filter also includes a shape retention structure capable of being connected to at least a portion of the filter media assembly and capable of retention the filter media assembly in the expanded state. A spacing distance between adjacent pleats in the filter media is greater in the expanded state of the air filter than in the collapsed state of the air filter. In some embodiments, the air filter is an HVAC air filter.

A power tool having a power tool housing, a motor, a tool moved relative to the housing by the motor, a fan rotated by the motor such that a fluid flow with debris generated by tool is moved into the fluid inlet by the fan and through the discharge outlet, and a filter that is removably attached to the power tool housing. The power tool housing includes a fluid inlet and a discharge outlet. The filter includes a filter media for separating the debris from the flow of fluid. The filter media defines a collection container for storing the debris. The filter also includes an opening through which the flow of fluid with the debris enters the collection container, and a valve that is moveable between a closed position, in which the opening is closed, and an open position, in which the opening is open. The valve includes a duckbill check valve.