I was browsing the topics on incubators and didn't quite find what I was looking for elsewhere. In the past, I've used a fish aquarium/water at the bottom/aquarium heater/tupperware box filled with vermiculite/seran wrapped lid. This worked alright for me, but I did lose probably more eggs than I care to admit. 
Now, I know about Hovabators, but haven't purchased one because I was giving my female leos a break from egg-laying(1 year break since when they last laid). Reading up on them, I think I don't understand how they work. Some that I read on have vents to allow fresh air to flow through the incubator. How does one maintain a 80% humidity inside one with this happening - or can this feature be sealed up?
The next time I have leo eggs, I didn't want to kill 50% of them. It was depressing when it happened in the home-made version, so I wanted some feedback on what everyone here thinks is best to use and how it is used properly.
Thanks everyone.

