So, I don't mean to be contrarian, but if this is about the Holocaust, remember that there are other ways to die. First they used bullets, but they cost too much and it's not particularly efficient. Then after that, they drove around in vans and picked people up off the street. They had the exhaust piped into the back of the van. The carbon monoxide poisoned the people in the back. This was a very well-known phenomenon. Remember "Ring around the rosey"? It was a children's song about the Black Plague. There was a similar song that children sang during the 1930s-1940s, about the vans. They were called "death boxes" in the song. It was in pop culture. The only reason they stopped doing it was that it wasn't really efficient either in the miles-per-gallon per passenger they could kill, or in the number of people that could be killed per day. Just like the guillotine was invented to make execution faster and more efficient, the showers in the concentration camps were used to kill more quickly and efficiently.