Patent ID: 8610087

Claim:
A method comprising: placing on a solid surface a first film or a superimposition of a number of films equal to or greater than two films, and wherein the first film or the films of the superimposition of films being sensitive to at least two distinct types of radiation including β − radiation; placing a second film directly onto the first film or the superimposition of films, wherein the second film being sensitive to at least two distinct types of radiation including β − radiation; waiting for a determined lapse of time; developing the films; and determining locations of the solid surface that are polluted by β − radiation emitting entities by identifying locations on the first film or a film of the superimposition of films positioned closest to the solid surface that correspond to β − radiation through a comparison of the first film or the film of the superimposition of films positioned closest to the solid surface to the second film after their development, wherein the number of films is determined so that no β − radiation reaches the second film.