When did they install walk-through explosive detectors at the CN Tower? I was there in July 2001 and don't remember going through any machines.

Adding 10 seconds to the time it takes to go through the metal detector would severely restrict throughput given the lack of capacity to expand most security points (this is already a problem today). Add more time to go through the shoe scanner, plus more time to put one's liquid items through the liquid scanner, and you may as well just give up and close the airport.