' ▁cl othing ▁for ▁sh ipping ▁was ▁performed ▁by ▁Son der k omm ando ▁work - details . ▁The ▁work sh ops ▁for ▁the ▁Jewish ▁prisoners ▁and ▁the ▁bar ra cks ▁for ▁the ▁Ukrain ian ▁gu ards ▁were ▁separated ▁from ▁the ▁" processing " ▁zone ▁behind ▁an ▁emb ank ment ▁of ▁the ▁old ▁Otto ▁Line ▁with ▁the ▁bar b - wire ▁on ▁top . ▁Most ▁Jews ▁from ▁the ▁cor pse - unit ▁( the ▁T oten jud en ) ▁were ▁killed ▁period ically ▁and ▁replaced ▁by ▁new ▁arrival s , ▁so ▁that ▁they ▁would ▁neither ▁organ ise ▁a ▁revol t ▁nor ▁surv ive ▁to ▁tell ▁about ▁the ▁camp ' s ▁purpose . ▁The ▁German ▁SS ▁and ▁the ▁administration ▁were ▁hous ed ▁in ▁two ▁c ott ages ▁outside ▁the ▁camp . ▁ ▁Camp ▁operation ▁▁▁ ▁The ▁Be ł ż ec ▁history ▁can ▁be ▁divided ▁into ▁two ▁( or ▁three ) ▁periods ▁of ▁operation . ▁The ▁first ▁one , ▁from ▁ 1 7 ▁March ▁to ▁the ▁end ▁of ▁June ▁ 1 9 4 2 ▁was ▁marked ▁by ▁the ▁existence ▁of ▁smaller ▁gas ▁ch amb ers ▁hous ed ▁in ▁bar ra cks ▁made ▁of ▁pl anks ▁and ▁ins ulated ▁with ▁sand ▁and ▁rub ber . ▁Be ł ż ec ▁was ▁the ▁first ▁killing ▁centre ▁of ▁Operation ▁Rein hard . ▁There ▁were ▁many ▁technical ▁difficulties ▁with ▁the ▁early ▁attempts ▁at ▁mass ▁ex termin ation . ▁The ▁g ass ing ▁installation ▁was ▁imper fect ▁and ▁usually ▁only ▁one ▁or ▁two ▁rooms ▁were ▁working , ▁causing ▁a ▁back log