A lithographic projection apparatus (1) includes a support configured to support a patterning device (MA), the patterning device configured to pattern the projection beam according to a desired pattern. The apparatus has a substrate (W) table configure to hold a substrate, a projection system configured to project the patterned beam onto a target portion of the substrate. The apparatus also has a purge gas supply system (100) configured to provide a purge gas near a surface of a component of the lithographic projection apparatus. The purge gas supply system (100) includes a purge gas mixture generator (120) configured to generate a purge gas mixture which includes at least one purging gas and moisture. The purge gas mixture generator has a moisturizer (150) configured to add the moisture to the purge gas and a purge gas mixture outlet (130) connected to the purge gas mixture generator (120) configured to supply the purge gas mixture near the surface.