A combustion air filtration apparatus for filtering combustion air for an engine is disclosed. The combustion air filtration apparatus comprises a combustion air source and a filter system fluidly coupled to the combustion air source and to the engine to receive combustion air from the combustion air source and to supply filtered combustion air for the engine. The filter system comprises a first combustion air filter, a second combustion air filter flow-parallel to the first combustion air filter, and a flow control system fluidly coupled to the first combustion air filter and the second combustion air filter to direct flow of combustion air selectively between the first combustion air filter and the second combustion air filter.