Zyklon B, the deadly chemical used in the gas chambers during the holocaust, was developed by two firms. One Tesch/Stabenow supplied two tons of Zyklon B every month while the other firm, Degesch, supplied the camps with only three quarters of a ton every month. Both companies used t be in business with pest extermination, such as rats or insects. After the end of the war the directors of the firms denied knowing that nazis were using their product to kill humans. After finding letters from two partners of Tesch/Stabenow explaining how to use the Zyklon B they were sentenced to death and hanged in 1946.
"Hoess testified that the Tesch directors could not help but know of the use for their product because they sold him enough to annihilate two million people."(http://www.nizkor.org/faqs/auschwitz/auschwitz-faq...
Zyklon B is usually used as a powerful insecticide that carries the gas Hydrocyanic Acid or HCN. It usually comes in the form of pellets or disks which react with iron and concrete to make hydrocyanic compounds that are deadly to humans. Traces of HCN were found in runs of gas chambers. HCN is more deadly to warm blooded animals than insects and the concentration in delousing operations can have exposure times up to 72 hours long. The exposure time for most of the extermination operations would be around 15 minutes. If a high enough concentration is used then it is possible for HCN to cause an explosion and although the SS did use a concentration higher than the lethal amount it was no where near the amount needed to cause an explosion. After using Zyklon B to exterminate pests in a house it should not be reentered for up to 20 hours after but since the bass chambers were forcibly ventilated the chambers could be reentered in about fifteen minutes. When ventilation was not used, prisoners would be sent in to carry out the bodies with gas masks on.
This is a diagram of a delousing room in Auschwitz, the operator would begin the process by opening the can of Zyklon B and putting it in the room. Hot air would be ventilated throughout the room which would begin the vaporization process, after it has been in the room for an allotted amount of time the air would be blown out into the exhaust pipes so the room can be aired out. After the room has been exhausted the operator is then allowed to reenter the room while using a gas mask.
The use of Zyklon B in the gas chambers of concentration camps led to one of the most infamous genocides in human history.
"Auschwitz: Zyklon B." Auschwitz: Zyklon B. N.p., n.d. Web. 11 Dec. 2014.