EXOTIC OPTIONS TESTED FOR AIRPORT SCREENING

WASHINGTON - JUST as travelers may be getting used to the familiar and
ever-more-sensitive metal detectors at airport checkpoints, the
Transportation Department is evaluating more sophisticated and exotic
equipment to screen the one billion or so people who go through such
portals in the United States each year.

Contractors, sensing a lucrative new market, have built prototypes of
scanning systems that will sense tiny particles of explosives as well as
drugs. The sensors can register as little as a nanogram, or one billionth
of a gram.

Trace detectors, as such machines are called, are in use at about 50
airports, but for carry-on bags, not people. In their present form they
would be awkward to apply to people, even more awkward than current
security procedures. Trace detectors are commonly used on laptop computers
and other fairly large objects that could conceal a bomb that X-rays cannot
detect. A technician runs a muslin cloth over the object, then feeds the
cloth into a machine that looks for telltale chemical compounds.

A new machine being tested at the Federal Aviation Administration
laboratory at Atlantic City International Airport in Egg Harbor, N.J., has
passengers walk through a portal somewhat bigger than a metal detector,
with a chimney on top. A red light tells the passenger to stop and a
recorded voice announces, "Air puffers on." A little puff of air -
resembling a glaucoma test, but for the whole body - shakes particles loose
from the skin and clothing, then rises up to the chimney for analysis. If
the sample shows nothing suspicious, a green light tells the passenger to
move on.

The manufacturer, Xtek, of Wilmington, Mass., says that the machine, which
it calls EntryScan, can pick out explosives such as C4, Semtex and
dynamite, and cocaine, marijuana and other substances, all of them
"effortlessly detected and identified in a nonintrusive manner."

Nuclear power plants have used such systems for years to test for signs of
explosives. But those systems are much too slow for airports. Power plants
can take a minute or so for each person; the units being tested in Atlantic
City take a few seconds.

Presumably a trace detection system would tip off screeners to passengers
like Richard Reid, the man who officials say had a bomb in his shoe and was
trying to blow up an American Airlines flight from Paris over the Atlantic
in December.

Another company, the Thermo Electron Corporation, builds a portable system
called Egis, used in airports overseas, that works on the same principle.
It can be moved around in a van. The company's Web site says the device can
be used after a bomb blast to analyze the explosive used, and has a picture
of a site where that was done: the World Trade Center after the 1993 bombing.

Such systems have several challenges. One is to run reliably in the field;
much of the equipment installed by the airlines and by the new
Transportation Security Administration has a tendency to break down,
according to airline officials.

Another is that at present, there is no performance standard by which the
equipment would be certified for use. And some people could set them off
for innocent reasons - after having come from a firing range, for example.

But trace detection is promising, according to Dr. Susan F. Hallowell, the
manager of the explosives and weapons-detection research and development
branch at the Atlantic City lab, because nearly any bomb builder would
carry traces of explosives afterward. "I can make a clean bomb, but I have
27 years' experience," she said. A bomb maker who washed his hands
afterward would recontaminate his hand when he turned off the water faucet,
she said. And people who wash their hands may not have washed their clothes
or their wristwatches.

Dogs could do the same work, but security officials say that the dogs tire,
lose interest and stop working, without indicating that they have done so.

Trace detection has the advantage of requiring minimal judgment by the
screeners, who can also lose focus on their work. A reliable system would
also be embraced by the airlines, which fear that the intrusive searches at
checkpoints now are driving away passengers. But some airlines would like
even better inspections at the checkpoints. Don Carty, chief executive of
American Airlines, said recently that if the universal searches were more
thorough, the Transportation Security Administration might be able to skip
the second round of searches at the gates.

Another technology undergoing tests here is body scanning using backscatter
X-ray, in which tiny doses of X-rays are bounced off the person to be
scanned, giving a view through the clothing. The Transportation Security
Administration does not use the machine, but officials said that the
Customs Service offers it in lieu of a strip search. "There are obviously
some issues with deploying this," Dr. Hallowell said.