Despite worries about the reliability of airport "puffers" that can detect explosives on passengers, the five machines at Salt Lake City International Airport have performed satisfactorily since they were installed in April, Transportation Security Administration officials say.
Even so, the agency has put off stationing more of the "explosive trace portals" at U.S. airports until it decides whether to alter them or wait until better puffers are available. Citing security concerns, the TSA will say only that software problems led the agency to suspend installation of more puffers.
Views outside the agency about the portals vary widely. Proponents say puffers make them feel safer. Critics claim puffers invade their privacy and slow security screening.
Many people still don't know the devices exist, even though 250,000 people pass through them at Salt Lake's airport every month.
"I don't really see much benefit," said Sandy Flieger, who flew from Seattle to Salt Lake City on business. "I don't think [puffers] will speed up the process, and that would be the only benefit I could see."
Andy Kuehn, who was preparing to fly home to El Paso, Texas, took a different view.
''Of course it slows it down," he said. "But I'd rather spend an extra 15, 20, 30 minutes so everybody can be checked."
The TSA began testing puffers in five airports in 2004 to see whether the devices could detect explosives without slowing down passenger screening. Since then, the agency has put about 90 puffers in 30 airports, spokesman Nico Melendez said. Roughly half were bought from Smiths Detection, a New Jersey-based firm; the rest were made by General Electric.
Each machine costs $160,000. None of them has ever discovered explosives on people attempting to board an airplane.
The puffers in Salt Lake City's airport came from GE. Two are at security checkpoints in Terminal One. Another pair is in Terminal Two. The fifth is in the international terminal.
"I think the jury is still out on just how effective they are," airport Executive Director Roy Williams said. "If they are defective, they should be pulled. But clearly it's desirable to get to some system that does accomplish the objective of detecting explosive traces."
Puffers don't replace walk-through metal detectors. Passengers selected for secondary screening step into a phone booth-size chamber where air is puffed onto them, starting from the bottom up. The air is drawn up in a plume to a sensor by way of a convection current created by the body, which eliminates the need for fans that could stir up contaminants.
The sensor compares the speed of molecules in particles knocked loose from the passenger to the speed of molecules of known threat substances. An alarm is triggered if there is a match. The process takes about 20 seconds.
Puffers are complex machinery, said Ron Malin, security director for the TSA in Utah. They shut down if a filter clogs, a part malfunctions or because they must be recalibrated. Despite that, puffers are as dependable as other screening equipment, he said.
"When it's working, it works as designed and it's nothing that I'm concerned with," Malin said. "It doesn't stop the process. It doesn't stop people from getting on airplanes. The failure rates are not outside the manufacturer's specifications."
Puffers aren't new technology developed in response to the Sept. 11, 2001, terrorist attacks. GE has sold more than 300 puffers since 1997.
Most aren't used in aviation security, said Steve Hill, a GE Securities spokesman; they are widely used at nuclear power plants. Prison puffers are calibrated to detect drugs. Tourists entering the Statue of Liberty must pass through puffers sniffing out bomb material.
"Our machines are in place in Salt Lake City and are apparently working well," Hill said. "We are confident that the [puffer] entry scans that have been built to fairly stringent specifications by the customer, TSA, work as approved."