Many years ago, late 1950’s, I was making a large vat of sodium hypochlorite (think bleach) by bubbling chlorine gas from a chlorine gas canister through a solution of sodium hydroxide. It was super stuff, twice the concentration of store bought. We use it for water treatment in commercial cooling systems, and for swimming pool maintenance.
One day a line came off the tank and started filling a rather confined area with chlorine gas. I put a wet cloth over my face and went into the area to turn off the tank. Then cleared the air in the area. Chlorine is pungent, corrosive, and deadly. Not a good experience. Btw, I have no ill effects from my experience.
This system that almost killed me was chlorinating the cooling tower basin that cooled the condensers at a power plant. Oddly, we couldn’t seem to chlorinate enough to kill the algae. We sent a sample to the company’s lab, and they said this algae LIKED chlorine.