So the Mayor knows it all?

I arrived to work this morning and within a half hour had a very bad headache. There was an odor of gas and the building was temporarily evacuated. I already didn't feel well and no one seemed to know what was really going on so I left and I'm working from home. This is what the mayor was saying on the news.

"It may just be an unpleasant smell, but at this point we don't know anymore than that," New York Mayor Michael Bloomberg said at a press conference Monday. "One thing we are very confident of is it is not dangerous, but how long and what the sources are, we just don't know."

If they don't know what it is, how does he know it's not dangerous? I wasn't taking any chances.