Answer:
Depends on where the gas chamber was. Many chambers were on railcars people thought they were going to the camps then they released blue pellets called Zyclon-B a common cheap efficent way to kill Jew's. The other ones were big enough to fit 20-30 people they were told they were getting showers but really they were being murdered on the spot. After the chambers they took the dead bodies to the crematoria and threw them in the oven.