I have a SWG. Needless to say, outside of a green pool opening, I rarely have to deal with chlorine. When I do, I typically use liquid bleach. Last week I was sick with a stomach virus on top of being 6 months pregnant, so I was not able to monitor my water chemistry for about 5 days. I also forgot that my SWG was only set to 10%. That, coupled with several days of on/off rain, caused my FC to tank. By the time I was well enough to check it, I was at zero and I knew an algae bloom was looming. I cranked the SWG but I knew I needed an alternate source to get things up quickly.
Not realizing I had liquid hiding in the shed, I went for a container of mini chlorine tablets so I could get something in there before I went to the store. It was a container from the end of last season. Something had taken place inside, and when I opened it (not near my face), I was met with a very powerful gush of chlorine gas. Let me tell you, I would not wish it on my worst enemy. The burning in my eyes, nose, and chest was so violent. I was very close to having my niece call 911, but calmed myself enough to call poison control. I could only get 2-3 words out at a time between coughing. They reassured me that an inhalant injury probably would not harm baby, and we discussed when or if it would be appropriate to go to the ER. After about 30 minutes in fresh air I was able to calm my breathing, but continuously coughed for 2 more hours before finally passing out from exhaustion and sleeping for an hour. After that, things were much better but I had discomfort with deep breathing for the next day or so.
After allowing the open bottle to aerate, I cautiously examined it and noticed that some of the tablets appeared charred, but there was no indication of an abnormality on the outside. I am upset with myself for taking for granted that these are powerful chemicals--it was not properly stored and old. I should have known better. Please, if you are a pool care amateur, learn from me and be careful!!