On tonights ride I was passing a farmer when I smelled Ammonia. I was well into my 80% range of maximun heart rate and had taken two breaths before I realized I was breathing anhydrous ammonia. A farmer was spraying a field about 70 yards north of me. As soon as I realized it was anhydrous ammonia, I held my breath as long as possible, but this proved to be difficult at this rate of physical excertion. I forced to take many short breaths until I got upwind of the farmer.
I had decided to keep riding to pump as much fresh oxygen into my system as possible. In less than a half-mile my lungs and legs began to burn, so I stopped for a drink. I still felt it was best to keep riding and provide maximum oxygen to my cells. After a two minute rest, I continued on because there was no indication of feeling light headed or dizzy.
It seemed silly at the time, but while I was holding my breath, I wondered how many other riders have attempted this. The reasons could be countless, such as sewers, road kill, or other nasty odors. Anyway, my research suggested that there should be no long term effects.