DO NOT use old coconut oil!
This just happened tonight, but let this be a lesson for you all.
I opened and used some louana liquid coconut oil. Still within the expiration date, but I must have had it a bit longer than I thought or something. It didn't smell off before cooking, and it didn't look any different, but when I put in a bit and turned on the kettle, the difference was immediate and painful.
The smoke that comes from rancid oil is insanely potent, it burns your throat and lungs. It tasted like the same acidic taste you get after getting sick, but times 100.
The house absolutely reeks and I have fans going with candles and incense. Not much has fixed it.
I plan on doing a deep clean on my machine tomorrow (8oz lincoln machine) after the smell dims a bit.
If you are worried about old oil, even if its in the expiration date, just put a tiny amount in, and turn on the kettle.