From one of the manufacturers: https://support.farberwarecookware.com/support/solutions/articles/65000168119-is-nonstick-cookware-harmful-to-my-pets-

Long story short, accidentally burning a PTFE coated pan will release chemicals that are bad for you and your pet. No matter how that manufacturer softballed the answer, it’s right there: the fumes of overheated plastic are harmful.

You weigh much more than your pet, so the time it takes for the resulting toxins to approach LD50 for a human are quite long.

Zipping a smaller, faster breathing pet’s blood levels up to fatal are unfortunately much easier, almost by an order of magnitude depending on the pet. That article references birds as most sensitive (see: canaries in coal mines), but dogs and such being close to the floor will also get a lot of exposure to the heavy gas particles.