A filter is provided for removing contaminants from a gas flow (e.g., an air flow). Multiple panel filters are arranged in a filter housing. The panel filters are arranged parallel or near-parallel to a main gas flow direction and spaced apart to define elongated gas flow channels between adjacent panel filters, each elongated gas flow channel extending generally in the gas flow direction. The elongated gas flow channels include inlet channel(s) and outlet channel(a) arranged in an alternating manner, the inlet channel(s) configured receiving the gas flow at the inlet end and the outlet channel(s) outputting a filtered gas flow from the outlet end. Gas flow redirecting structures are arranged to redirect the gas flow in each inlet channel through adjacent panel filter(s) and into adjacent outlet channel(s). The filter may provide a pressure drop of less than 3 iwg, less than 1 iwg, or less than 0.3 iwg.