Most of the things that burn
Most of the things that burn off in the kiln – most glues, shelf paper, fiber board/paper binder, etc. – produce only nuisance (i.e. non-toxic) fumes. Some people are more sensitive to them than others. When in doubt, request a MSDS (manufacturer’s safety data sheet) from the manufacturer. That will tell you if you need to be concerned.
As for the glass, that should not be a worry. Even lead crystal can be melted in a kiln without much concern (http://www.gafferglass.co.uk/technical/casting_main.htm).
Helios Kiln Glass Studio