Empty, Minimum and Maximum load for autoclave

Dear Forum,

As mentinoned in most guidelines; autoclave performance re-qualification normally must be tested using heat distribution and penetration for:

a) Empty chamber.
b) Minimum load, and
c) Maximum load.

Can we skip the ‘Minimum Load’ study? It really seems unnecessary because we already covering the study from empty chamber up to full loaded chamber.

Minimum load is worst case for evacuation of air for loaded chamber…

minimum is worst case as a sterility challenge also. If I had to pick between min and max, I would do minimum loads always. Maximum loads typical have longer ramps and therefore the accumulated lethality is greater.

Dear All,

I’ve got this explanation fom Autoclave Sifu; Mr. Agalloco’s presentation.


Slide 38 of 61;

  1. He explained that some company validating minimum load by using a single tray or a box.
  2. There are firms which has validate only maximum load, and any load smaller than maximum is made up to maximum by dummy units.

Can anybody elaborate on this?

1 Like

Minimum load is not defined by the regulatory agencies as empty chamber. We had an inspection by both the US (FDA) and EU (EMEA), since we sell products to Europe, EN 285 has a more stringent requirement.

Through your cycle development, you should have data to prove which article in your load configuration takes the longest to heat up. This single article is your minimum load.


We only do maximum load every year (not for product but vials and equipment). We pass FDA inspections and no problem with this issue.

Dear All,

Since all these years my company only do heat distribution and heat penetration for empty & max load for our rubber stopper (aseptic process). Without naming which PIC/S authority, my company was given a finding because we never validate the minimum load for our rubber stopper sterilization.
We are really mad because we have to do minimum load not just for rubber stopper, but also for all other load cycle.

I think the regulatory body espescially the auditor need to understand that these PQ practices (empty, min and max) is costly and time consuming. We understood that it is compulsory for ‘Terminal Sterilization’. And most guidelines also prefer it that way. (Except PIC/S; which they didn’t have complete guidelines on 'terminal sterilization).

In a word, I would like to suggest that, we should simplify the autoclave PQ by :
1). skipping the minimum load study espescially for non-critical load OR,
2). we could just add ‘one empty tray’ as the standard min load study.