Sterility in the biosafety cabinet - (Dec/15/2011 )

I have a bit of a nitpicky question.

Let's say I am doing some work in a biosafety cabinet (which I will affectionately refer to as "the hood"). I've sterilized it, I've sterilized all my equipment, I've sterilized me, everything is sterile. I open a box of autoclaved pipette tips inside the hood.
I use a few, maintaining good laboratory practices while doing so. My experiment remains uncontaminated.
I close the autoclaved pipette tips inside the hood.

If I remove these tips from the hood, never opening them outside the hood at all, would the tips still be considered sterile? I.e., could I clean the outside of the box, replace it in the hood, open it and carry on as normal, or would they have to be reautoclaved before going back in the hood?

I hope this isn't a dumb question.
Thanks!

That is how work is normally done in biosafety hoods. For optimal performance, they should have as little stuff in them as possible, and be emptied before cleaning down after you have finished working.

bob1 on Thu Dec 15 20:01:00 2011 said:

Thank you!
I'm a new graduate student and my lab had been leaving the boxes stacked neatly in the hood. It worked well for a while (we have a very large hood, so they took up little space) but people started leaving other crap in there as well so everything's been stripped out. I've got my own stash of pipette boxes now but just wanted to check and make sure I wasn't going to contaminate anything.
Thanks again!

I remove my equipments every time (tip boxes, pipettes, etc). Just stick by this golden rule: sterilise everything which goes in and out. We use 70% Ethanol (w/w).
As long as you keep it sealed, it should be fine to reuse those tips.

Yes, we also wipe everything going in the cabinet (which we affectionately refer to as "the box") with 70% ethanol. Though we usually keep things belonging to the box (like pipettes and tips) inside. But when everyone leaves there everything once used inside, it becomes crowded, so I usually go mad and throw out all the unnecessities. And of course sometimes we need to completely clean it.

As long as they remain closed it should be fine, the problem with removing boxes and stuff from the hood is that if you leave the room, or leave them overnight, then you don't know if someone else has knocked them or opened them outside the hood or anything, rendering them unsterile. Personally we keep one box of each size of tip inside the hood and try and keep everything else outside, but if this is a problem then having your own box labelled and sealed with tape or something so they don't open if they get knocked should be ok to remove.