Editing Health physics (section)

===Installed instruments===
Installed instruments are fixed in positions which are known to be important in assessing the general radiation hazard in an area. Examples are installed "area" radiation monitors, Gamma interlock monitors, personnel exit monitors, and airborne contamination monitors.

The area monitor will measure the ambient radiation, usually X-Ray, Gamma or neutrons; these are radiations which can have significant radiation levels over a range in excess of tens of metres from their source, and thereby cover a wide area.

Interlock monitors are used in applications to prevent inadvertent exposure of workers to an excess dose by preventing personnel access to an area when a high radiation level is present.

Airborne contamination monitors measure the concentration of radioactive particles in the atmosphere to guard against radioactive particles being deposited in the lungs of personnel.
    
Personnel exit monitors are used to monitor workers who are exiting a "contamination controlled" or potentially contaminated area. These can be in the form of hand monitors, clothing frisk probes, or whole body monitors. These monitor the surface of the workers body and clothing to check if any [[radioactive contamination]] has been deposited. These generally measure alpha or beta or gamma, or combinations of these.

The UK [[National Physical Laboratory (United Kingdom)|National Physical Laboratory]] has published a good practice guide through its Ionising Radiation Metrology Forum concerning the provision of such equipment and the methodology of calculating the alarm levels to be used.<ref>Operational Monitoring Good Practice Guide "The Selection of Alarm Levels for Personnel Exit Monitors" Dec 2009 - National Physical Laboratory, Teddington UK [http://www.npl.co.uk/upload/pdf/alarm_levels_personnel_exit_monitors.pdf] {{Webarchive|url=https://web.archive.org/web/20130513191645/http://www.npl.co.uk/upload/pdf/alarm_levels_personnel_exit_monitors.pdf |date=2013-05-13 }}</ref>