Sodium Hydroxide is what is in Drano - definitely dangerous.
Some number of people had the misfortune to pick up one of these pressurised cans. When they went to open it, they experienced a pneumatic blowback and were sprayed, typically on the hands, arms and face, with Drano.
The lawsuits were hugely expensive...and from that date, Drano is formulated differently and is sold in cans with a plastic cap which will pop open automatically if the internal gas pressure becomes too high. '