For a gas turbine, rarely is a single filter sufficient to reduce or eliminate particulates. Therefore, multiple stages of filtration are required. A filtration “stage” is simply a type of filter that is designed to remove either a specific contaminant or type of contaminant from the air or is designed to filter a specific particle size from the air to protect the next stage of filtration from being overwhelmed.

As an example of a multi-stage filtration system, a turbine may have:

• A Louver
• A trash screen
• Anti-icing
• A coalsecer
• A vane axial separator
• A bag pre-filter

• A rectangular pre-filter
• A high-efficiency cartridge filter
• A high-efficiency Rectangular filter
• A self-cleaning cartridge filter