This thread is from 2014. This member seldom posts anymore and is unlikely to see your question.Isn't it bad to have a perfectly closed chamber because then you have to worry about bacteria growth and the health affects associated with poor ventilation
A closed chamber is not airtight. There is plenty of air movement, but not so much that your heat and humidity are wicked away. A closed chamber allows you to reduce ventilation to workable levels, not eliminate it.
Bacterial growth is not an issue if you spot clean daily and use the recommended substrates that resist bacterial and fungal growth.
As far as health effects, the effect of a closed chamber on baby tortoises is that they thrive. This type of environment most closely simulates what we speculate they experience in the wild hiding in the thick undergrowth in a humid, rainy, hot climate. I say "speculate" because very little is known about where they go after hatching. The lost years... Since we don't really know what happens in the wild, we are left with what we see in our own enclosures every single day. The dry routine results in one outcome, and the closed chamber routine result in a different and much better outcome, time and time again.
What species and size tortoise are you housing? We can link the correct care info for you.