Explosives at forefront of airport security measures.

• Author: Jean, Grace
• Position: HOMELAND DEFENSE

THE TRANSPORTATION SECURITY Agency modified its list of prohibited items in carry-on luggage in December. This marked a shift from the post-9/11 focus of preventing terrorists from taking over airplanes to thwarting would-be bombers.

"I am convinced that the time now spent searching passengers' bags for small scissors and tools does not add to our security. These are not the tools of the terrorists. We must focus our attention on the far more dangerous threat of explosives," said the Transportation Security Administration assistant secretary Kip Hawley.

The popularity of improvised explosive devices as a weapon of choice for terrorists has prompted the TSA to continue installing screening machines that can detect explosives.

Darrin Kayser, TSA spokesman, said 59 explosives trace portal machines have been installed at 24 airport security checkpoints across the country.

Slightly larger than the walk-through metal detectors, these portals require passengers to step inside one at a time and stand still for a few seconds as puffs of air blow particulates off their clothes from head to foot. Within a matter of seconds, the machine analyzes any microscopic particles knocked loose for traces of explosives. If none are found, a computerized voice will tell passengers to exit the portal. But if it discovers any positive results, the machine will immediately alert screeners.

Kayser said the agency is in the process of...