Thanks Paul,

The instrument is a TIF 8800 gas detector...I own one. These devices "click" and the clicking speeds up when gas is detected. The clicking turns into a "scream" when the sensor is saturated with combustible gas. His detector was "screaming" which means "danger".

I just found this video which reports a gas leak at the high school across the street from the towers. Everyone was safely evacuated. Very suspicious. IMHO.

http://www.youtube.com/watch?v=R_fg7eashn0&feature=related