The invention relates to a method and apparatus for detecting substance to be detected. The apparatus comprises at least one sampling member for sampling air contained in a closed space, the sampling member comprising at least one filter presenting pore or mesh size adapted to filtering solid particles of the substance to be detected that might be dispersed in the air contained in the closed space; the apparatus further comprising a pump (not shown) enabling the air contained in the closed space to be sucked in. The invention can be used for detecting a substance to be detected comprising, for example, an explosive or a narcotic.