A lithographic apparatus is disclosed. The apparatus includes a projection system configured to project a first radiation beam onto a target portion of a substrate, and at least one monitoring device for detecting contamination in a interior space. The monitoring device includes at least one dummy element having at least one contamination receiving surface. In an aspect of the invention, there is provided at least one dummy element which does not take part in transferring a radiation beam onto a target portion of a substrate, wherein it is monitored whether a contamination receiving surface of the dummy element has been contaminated.