Problem with oil drums is you never know what they have been used for, not always what it says on the tin.
Few years ago one of our customers rented an extra bit of land at the end of his for parking trucks.
he got some driver to clean all the crap off so it could be leveled.
One driver got this drum and shook it and they was something in it, so like 99% of all of us he unscrews the bung and took a sniff.
Bang out like a light, it was only the fact that he was literally 3 minutes away from a main hospital that he survived as they threw in in a pickup and rushed him straight in, no waiting for an ambulance. Turns out this drum had some waste cyanide in it from somewhere.
Frightening thing was he didn't do anything that any one of us would have done at the time.