Wow, what I coincidence!  I work in a clean room too, doing medical assembly work.  I don't have to wear a hood like yours, though, just a little bouffant cap.   

My hair isn't very long yet.  It only reached the tops of my shoulders in September, so really all I can do with it is pull it into a ponytail, or hold it back with a headband.

On the one hand, the cap doesn't move all that much, so I haven't been too worried about how it might affect my hair.  But lately I have noticed that my hair does look a little 'frizzed' when I remove the cap.

To remedy this, I've been considering maybe wearing a bandanna made of a hair-friendly material.  I don't know if you have any restrictions on what you can wear underneath your clean room gear, but you might consider something similar.  I hope this helps.   

Thanks!
No, there are no restrictions to what we can wear under the hoods.  A few muslim women I work with can wear their hijab with no problem.
I think I may stick with a loose bun covered with a bandana.  Do you think it would be better to let my hair down during breaks, or just leave it up?  I'm not sure what would be more damaging: leaving it in a bun, or taking it up & down several times throughout my shift.

Thanks again!