An exposure system for exposing a photoresist layer on a top surface of a wafer to light. The exposure system including: an environment chamber containing a light source, one or more focusing lenses, a mask holder, a slit and a wafer stage, the light source, all aligned to an optical axis, the wafer stage moveable in two different orthogonal directions orthogonal to the optical axis, the mask holder and the slit moveable in one of the two orthogonal directions; a filter in a sidewall of the environment chamber, the filter including: a filter housing containing chemically active carbon nanotubes, the chemically active carbon nanotubes comprising a chemically active layer formed on carbon nanotubes or comprising chemically reactive groups on sidewalls of the carbon nanotubes; and means for forcing air or inert gas first through the filter then into the environment chamber and then out of the environment chamber.