And they were in sealed gas chambers!
Imagine the luck of the Nazis that they miraculously managed to carry out thousands of gassings in massive outdoor rooms in polish winter with wooden doors and were able to remove the bodies instantly even though hydrogen cyanide stays lethal for so long afterwards!
Of course any intelligent person knows the holocaust is about as real as bigfoot or viruses etc.
IIRC, they would make the prisoners stand in lines of a hundred and have them dig a pit beside themselves. When they were finished, they used one effective bullet to shoot the whole hundred and they would fall into the pit, which the next line would bury while digging their own pit. Then they did this 30 times a day for five years.
It may be unbelievable, but it happened!