A strainer/filter unit for effectively collecting solid, liquid or gaseous substances at the source and the method of using the strainer/filter unit. The strainer/filter unit includes a housing, a one-way valve at one end of the housing, and a filter having a certain depth and thickness within the housing. The filter is formed from a plurality of layers of material with pores such that pores of one layer partially overlap pores of subsequent adjacent layers. Matters entering the strainer/filter unit are collected in the filter while travelling through filter via a tortuous path.
