A long time ago, some one "accidentally" discharged a dry-chem fire extinguisher at the station. Didn't make much of a mess, but there was still one. Went and got the mop bucket, made up a bleach solution in the bucket that had some "water" in it still. Later during the day, a few of us started to get dizzy and noticed a nice greenish haze coming from the bucket. Went outside to get fresh air, felt better. Right around that time, someone else had showed up and asked what were doing outside. We explained it to him and his reply "you didn't use the blue bucket did you?". Well, long story short, he had used the blue bucket the day before using an ammonia solution. We had called up chemtrec (a poison control place), and inquired with them what would happen. Luckily, no one was harmed from this. Accidents can happen so quickly and easy. Often, VERY dangerous.
Congrats to the FD and EMS for a quick and safe evacuation.