Ammonia is a colorless, corrosive, alkaline gas that has a very pungent odor. It is one of those chemicals that just exists on earth as part of everyday life so there is really no way of getting away from it. Honestly, as part of nature, the quantities are so minute (1-5 parts per million in air, soil, and water) they pose no risk. Ammonia enters our body through breathing or ingestion, is in our bloodstream in seconds, and leaves through elimination a couple days later. We aren't really worried about the natural ammonia present in the world here... we are very worried about the concentrated, manufactured ammonia.
According to the CDC, the safe limit for worker exposure is under 50 parts per million. Standard cleaning solutions for home are 5-10% ammonia. For commercial use, they are 15-25% ammonia. Have you looked at your home products recently? If we look at a calculation of 10% pure ammonia in a product and utilize an online ppm converter, we see that 10% of a solution would be 100,000 parts per million.
Why, then, is this allowed? Well... you are breathing it in in unison with fresh air, so on a lung standpoint, you should be getting around or less than the parts per million acceptable safe level -- providing you are in a well ventilated space. Oh, and of course... they are assuming you are wearing gloves when you clean with a caustic and corrosive agent like ammonia.
"Funny, I remember spraying Windex on the windows as a kid and no one ever telling me I shouldn't breathe it and I should put on gloves. I cannot tell you how many times I have touched ammonia. When my hands would get all red and irritated, I KNEW it was because I was doing a darn good job cleaning everything. Needless to say, older and wiser, we skip this one in our house... my kids couldn't identify Windex in a line up (and this makes me one proud mama)."
-Amanda Uribe, YL Diamond