The Nizkor Project and other sources have stated that the minimal concentration of Zyklon-B to be explosive is 56,000 parts per million, while the amount used to kill a human is 300 parts per million, as is evidenced in "The Merck Index" and the "CRC Handbook of Chemistry and Physics". In fact, the Nazis' own documentation stated "Danger of explosion: 75 grams of HCN in 1 cubic meter of air. Normal application approx. 8–10 grams per cubic meter, therefore not explosive."