There were two videos available online (neither is extant now, one was titled "The Experiment") in which individuals had constructed a phone booth-sized enclosure out of wood. They had large windows in the doors. One of the videos was authored by a man named Mike Farrell, who I knew personally. Not sure if it's still made, but these two individuals acquired cans of Zyklon B, and they didn't look aged. They poured them out on the floors of the enclosures, sat in a chair that had been placed inside, closed the doors, and were on continuous video for over an hour. No problems. I would do this myself, with no worries, no doctor, etc. It is slightly more dangerous in humid environments, like Auschwitz, but not that much.
You see, Zyklon B is an insecticide, not a human extermination agent. Zyklon B is made from balls of pressed diatomaceous earth (calcium carbonate) or wood dust, which has been exposed to pressurized hydrogen cyanide gas. The balls absorb a small amount of this gas, and it takes from one to three days to release it. The IG Farben company wasn't trying to kill off it's insecticide customers, you see. All the stories from "survivors", by the way, involve the camp guards pouring a can or cans of Zyklon into open holes on the roof of the gas chambers, and 15 minutes later, "the screaming stopped". Stories also speak of guards and inmates standing around outside and smoking, which wouldn't be very wise, if there was enough cyanide gas to kill. It is highly explosive.
Zyklon B is purposefully confused (by the "survivors" and promoters of the holocaust myth) with the cyanide systems used in the US penal system. In those, a goodly amount of a cyanide salt (ounces of sodium or potassium cyanide) was dumped into a strong mineral acid (sulfuric or hydrochloric acid). This produces an instantaneous and energetic release of a large amount of hydrogen cyanide in a small, enclosed area. Unlike Zyklon B, very much unlike it.
By the way, when you are poisoned by cyanide, it instantly bonds to the hemoglobin in the blood, making it ineffective at carrying oxygen to the cells. Pardon my language, but the whole body goes ape shit, being suddenly starved of all oxygen. There are severe convulsions, in most cases. These are often sufficient to break the arms, legs, and spine. The body also takes on a blue color (cyan, thus the name "cyanide"). Death often takes as long as 15 minutes, meaning there is often time for severe swelling to occur at the point of bone breaks. These features are notably absent in photographs of "gas chamber victims". They are also notably absent in pics of the Jonestown massacre victims, moreso because those are color photos. I guess they figured the cyanide lie worked so well the first time.
The reason you will never see a video of a gas chamber execution in the US prison system is that it is a very cruel and unusual punishment. That's why it was discontinued. A website that advocates for a person's right to commit suicide offers a book on methods, including cyanide. The book notes that death by cyanide is "often violent".
This is one reason they need laws to protect the Holocaust myth. Any objective study of the subject shows how ridiculous it is. And if the Nazis did not carry out genocide.....