This happened about 2 years ago.

I had graduated from university the year before and some of my friends were still there. They were renting a house to stay in and I was visiting for a few weeks (long story, I was evacuated from the city I lived in). This happened at the beginning of summer and no one really had any responsibilities so we decided to set up a portable pool in the back yard. We filled it with the hose and bought a container of solid chlorine tablets to disinfect the water. We attempted to heat it up by boiling water on the stove but it didn’t really work (water takes a LOT of energy to heat up) so we just had a cold pool. We had a bunch of friends in the city nearby so there were always a bunch of people over hanging out. It was a great time.

After about a week the landlady showed up saying the water bill was astronomical and demanded we get rid of the pool immediately. Apparently they guys who rented the house didn’t pay for water so this was fair. I don’t think there was anything explicit in the lease agreement forbidding having a pool but it wasn’t unreasonable for her to be upset. Anyway we drained the pool but didn’t clean everything up right way because it started to rain pretty hard and we were all lazy. We just left all the pool stuff in the back yard for 3 or 4 days.

Unfortunately by the time the weather cleared up I was the only one left at the house so I had to clean everything up myself. As I was picking up empty cans from the corner of the yard I found the container of chlorine tablets. It had been left out for two weeks and gotten rained on. It kind of looked like the lid wasn’t screwed on properly and I wanted to make sure no water had gotten in (I was hoping to use them again later). I took off the lid, and ignoring proper lab safety, I brought the jar up to my face and looked in.

Immediately it felt like my lungs were on fire. I dropped the jar and fell to my knees coughing. I spent about 10 minutes on the ground feeling like there was lava in my chest, and it was about an hour before I stopped coughing every 30 seconds. I looked up what to do and it said to seek medical attention if you start coughing up blood. Luckily that didn’t happen to me so I figured I was fine. I did have a semi bad cough that lasted for about 6 months.

TLDR; I let water get in a chlorine bottle and accidentally broke the Geneva Convention on myself.