Plastics tend to consists of carbon and hydrogen chains. See for example polycarbonate [1], polyetene [2] and ABS [3] (contains nitrogen). They might however contain all sorts of additives. In order to produce just water, carbon dioxide and nitrogen the burning must be carefully controlled [4] - in your experiment the burning was probably not complete, which explains the fumes (that might have been carcinogenic [4]).

[1] https://en.wikipedia.org/wiki/Polycarbonate

[2] https://en.wikipedia.org/wiki/Polyethylene

[3] https://en.wikipedia.org/wiki/Acrylonitrile_butadiene_styren...

https://en.wikipedia.org/wiki/Plastic#Incineration_of_plasti...

You generally don't want to burn halogenated plastics like PVC though. As I understand it that will release highly toxic dioxins (which cause cancer and birth defects among other things) unless they are incinerated at high temperatures.

I don't know why this is downvoted, it's correct - incineration of plastics is needs to be done at high temperatures to avoid this problem.

Maybe it was PVC. That releases plenty of nasties when you burn it.

Ditto, the sibling posts seem to cover it except for printed plastics, even if the plastic is good the printing probably wasn't/isn't.

"the fumes sure smelled like maybe I should be sterile by now"

You, sir, have just enriched the English language.