Another question: How many of these scientific tests of teflon's safety have involved direct inhalation in order to determine safety standards.
There's some misunderstanding going on here. Safety testing (involving rats typically) establishes several levels of concern. You find these listed on MSDS sheets. OSHA type numbers. Safe for 8 hours, one time exposure, various 'uptake' methods, and so on. These are typically levels where half the population suffers (there really is no 'drop dead' line). It's 'aimed' at humans, not birds (or insects). That's one set of tests.
It's my understanding that such tests involve a modest (but reasonable) number of animals. The important issue is such data is (once again) 'peer reviewed'. It passes 'reasonableness tests' by experts and is open to confirmation.
I'm pretty sure nobody made lab rats vape from PTFE........
An entirely different set of tests determines what level of those substances is being produced under varying conditions. As you point out, for teflon that's usually a number way way past the temperatures we're working at. Not even the most dedicated naysayers claim problems at say 450 degrees AFAIK?
These are
materials tests, not safety tests. You have to link the two to determine health risks. To find out if your gas stove is safe you need to test the stove to get data then compare that data to established (in other tests by different groups) to get 'the big picture'.
Bottom line is, at the temperatures we're working with here, basically
zero 'toxic fumes' happens. The best scientific instruments available cannot measure it. "Empirical evidence" (in this case sensitive equipment that would not tolerate extremely small levels to function) says there's nothing there from the teflon or anything else in the vacuum.
CO2 is toxic at high enough levels. Your breath contains a few percent. Your breath is not toxic....well not by those standards anyway. In the PTFE case it's not a matter of 'a few percent' the number for all practical purposes is zero. Doesn't happen.
Believe what you want (or just prefer glass for any other reason), but by traditional measures there is no scientific reason for concern (by that I mean no experiment has shown it, including those designed to do so).
OF