Accordingly, the IFRC demonstrated that cyanides were present in all of the facilities where it is claimed that they were exposed, i.e. all five crematoria, the cellars of Block 11 and the delousing facilities. Critics state that any attempt to demonstrate that the crematoria could not have functioned as homicidal gas chambers on the basis that they were not exposed to cyanide is unsuccessful, given that its presence in what remains of these facilities is incontrovertible, and write that all of the gas chambers were exposed to cyanide at levels higher than background levels elsewhere in the camp, such as living areas, where no cyanides at all were detected. In addition, tests conducted at Auschwitz in 1945 revealed the presence of cyanides on ventilation grilles found in the ruins of Crematorium II (thus also demonstrating that the Leuchter report was not the first forensic examination of the camp as purported in the title of the London edition). The historian Richard J. Evans argued that due to Leuchter's ignorance of the large disparity between the amounts of cyanide necessary to kill humans and lice, instead of disproving the homicidal use of gas chambers, the small amounts of cyanide which Leuchter detected actually tended to confirm it.