wagen % 2 2 & f = false ▁Chapter ▁ 3 . ▁A ▁new ▁and ▁better ▁method ▁of ▁killing ▁had ▁to ▁be ▁found . ▁The ▁gas - v ans ]. ▁p . ▁ 6 9 }} ▁had ▁proven ▁ins u fficient ▁for ▁the ▁project ed ▁number ▁of ▁vict ims ▁from ▁the ▁Hol oca ust ▁trains ▁arriv ing ▁at ▁the ▁new ▁railway ▁approach ▁r amp . ▁ ▁W irth ▁developed ▁his ▁method ▁on ▁the ▁basis ▁of ▁experience ▁he ▁had ▁gained ▁in ▁the ▁fixed ▁gas ▁ch amb ers ▁of ▁A ktion ▁T 4 . ▁Even ▁though ▁Z y kl on ▁B ▁became ▁broad ly ▁available ▁later ▁on , ▁W irth ▁decided ▁against ▁it . ▁Z y kl on ▁B ▁was ▁produced ▁by ▁a ▁private ▁firm ▁for ▁both ▁Bir ken au , ▁and ▁Maj dan ek ▁nearby , ▁but ▁their ▁infrastr ucture ▁differ ed . ▁Be ł ż ec ▁was ▁an ▁Operation ▁Rein hard ▁camp ▁meant ▁to ▁circum vent ▁the ▁problems ▁of ▁supply , ▁and ▁instead , ▁rely ▁on ▁a ▁system ▁of ▁ex termin ation ▁based ▁on ▁ordinary ▁and ▁readily ▁available ▁killing ▁agents . ▁For ▁economic ▁and ▁practical ▁reasons , ▁W irth ▁had ▁almost ▁the ▁same ▁carbon ▁mon ox ide ▁gas ▁used ▁in ▁T - 4 , ▁generated ▁with ▁the ▁tor que ▁of ▁a ▁large ▁engine . ▁Although ▁Hol oca ust ▁witness es ' ▁test imon ies ▁differ ▁as ▁to ▁the ▁type ▁of ▁fuel , ▁Er ich ▁F uchs ' ▁post war ▁aff id av it ▁indicates ▁that ▁most ▁probably ▁it ▁was ▁a ▁pet rol ▁engine