Air has to be removed from the chamber in order to get the super heated temperatures necessary for sterilization to take place.
This is accomplished through a bellows (or steam trap). When a working bellows senses air, it opens and allows the air to escape into the water reservoir.
When it senses steam, it closes and seals up the system
Where To Look
Start by removing the left side panel from the autoclave (the hinged side....same side where you add water). You can click here for instructions
Once the side panel has been removed, you will notice a lid on top of the larger water reservoir, with a hole in the center
Remove the lid by taking a screwdriver or dental pick and insert it into the hole on the lid, lift up the lid and set it aside
Now look inside the reservoir. As you are facing the side, look back to the left (rear of the autoclave) inside the water reservoir and you will see a small shelf
There you will see a piece of pipe sticking through. There are no fittings on it, it is just a piece of pipe
How To Test The Bellows
With the side panel & lid on the water reservoir removed, start a cycle. When the autoclave gets above boiling, watch the end of the piece of pope described above
If you see steam coming out of the pipe, then the bellows is bad and needs to be replaced
