After elimination of the chemical weapons, it is necessary to relieve the consequences of operation of the chemical weapons destruction facilities (CWDF). This study aimed to assess the results of such relieve activities from the hygienic point of view. The assessment allows considering partial conversion of the CWDFs' infrastructure for civil purposes. At four CWDFs, the sites of contamination of equipment and infrastructural components with degradition products of organophosphorous agents (OPA) and blister agents (BA) were identified. The technologies that enabled analysis of the samples taken were high performance liquid chromatography with tandem mass spectrometry, gas chromatography–mass spectrometry, gas chromatography–tandem mass spectrometry, and atomic absorption spectroscopy with electrothermal atomization. The analysis revealed contamination of building structures, equipment, utility lines, waterproofing, heatinsulating, and other materials inside the CWDF process buildings, regardless of their purpose, with OPA and BA degradation products. In the absence of hygienic standards and information on their toxicity, it was impossible to assess the hazard thereof. In all the samples taken, the residual content of toxic substances was below the limit of detection of the measurement methods applied, i.e., none was found. The article presents a methodology for a stepwise hygienic assessment of the CWDF infrastructure to be converted and develops recommendations for its subsequent safe use. The conclusions state expediency of development of hygienic standards for the OPA and BA degradation products and development and certification of the relevant measurement procedures.