Abstract: An apparatus for training a user in contamination surveillance. The contamination may be from a nuclear, bacteriological or chemical explosion or leak, for example. The apparatus is portable and can be carried by the user to various points of an exercise area. The apparatus includes a data store and an interpolation device. The data store stores data which is derived from a mathematical model of an assumed source of contamination and which defines the contamination levels at various locations within the exercise area at respective elapsed times after the assumed commencement of contamination. The interpolation device is responsive to first signals which define the location within the exercise area and to second signals which define the elapsed time when the user of the apparatus inputs the first signals. The apparatus also may include a display on which is shown the contamination level, and a keyboard from which the first and second signals may be input.