toxic gas

I was riding a bicycle along 5th and I Street and experienced a choking sensation that I felt from experience had to be an odorless, toxic gas coming from the direction of the Suarez building. This was about 12 15 in the afternoon, and I sensed it again shortly after 1 pm, an hour later. It choked at the time, so I instinctively held my breath, and I felt an unusual irritation even later, as the sensation disappeared a block further - each time.

This is very dangerous, right?