Plant radiation detectors that are operating in a high ambient gamma background are sometimes shielded to prevent the background swamping the detector. Such a detector may be looking for alpha and beta particles, and gamma radiation will affect this. Laboratory or health physics detectors, even if remote from nuclear operations, may require shielding if very low levels of radiation are to be detected. This is the case with, for instance, a scintillation counter measuring low levels of contamination on a swab or sample.