Oil Blackening and other Oil Issues | Model Engineer
On a small scale I wouldn't worry about lethal smoke when quenching in oil. The odd job done in a well ventilated space won't do any harm unless you have a pre-existing medical condition like Asthma. Fire is a much more likely hazard. Unpleasant fumes and the risk of a flash fire (when hot oil vaporises and then the whole cloud ignites) make it unwise to quench in a confined space. Avoid. The risk rockets with size; a red-hot hammer head is far more dangerous than a tiny clock part. Not tried it, but blackening with oil requires the metal to be hot enough to carbonise the oil. That's enough t...
Source: model-engineer.co.uk