By Leslie Miller
The Associated Press

WASHINGTON - Anyone who plans to set off fireworks on the Fourth of July, be forewarned: your pyrotechnics may delay you at the airport later.

Ultrasensitive equipment that can detect minuscule traces of explosives on suitcases and skin might raise suspicions at the security gate.

If there's Roman candle residue on a carryon bag, a government security agent probably will want a chat before the bag is taken aboard.

Ever since federal security screeners began checking baggage for weapons and bombs at airports last year, they've been discovering suspicious substances used for innocent purposes on air travelers' luggage.

Fertilizer, for example, can activate an alarm. That's why the Transportation Security Administration warns golfers to clean their shoes and clubs before heading to the airport.

Susan Hallowell, director of the TSA's security laboratory, said the equipment has detected residue on police officers after they've come off firing ranges, on people who set off avalanches for a living and on heart patients who take nitroglycerin tablets.

"The bad news is you get nuisance alarms," said Randal Null, the TSA's chief technology officer. "The good news is the equipment is doing what it's supposed to do."

This is the first Independence Day that the government will be inspecting all checked baggage. Carrying or shipping fireworks, sparklers and other pyrotechnics aboard airplanes has been illegal for years because of the fire threat.

The penalty can be severe: up to five years in prison and fines of as much as $250,000 for individuals, $500,000 for corporations.

"We need people to think before they come to the airport what they're bringing, what they're packing and how much time they're allowing," TSA spokesman Robert Johnson said. "All these procedures are in place to prevent weapons from getting on board aircraft and to keep bombs out of suitcases."

Residue from substances used in bomb making and other explosive pursuits can dissolve into the skin and stay for days. Particulates then can be transferred through touch to credit cards, clothing, watchbands and luggage.

Partly because of the new technology, the Federal Aviation Administration is anticipating more people will get caught this year carrying fireworks aboard airliners.

In many airports, screeners use trace detection systems to check for explosives on checked luggage. They also use trace detection on carryon bags that arouse suspicion when they pass through X-ray machines at passenger checkpoints.

The trace detection systems include wands that knock loose particulates from surfaces. The particulates are then analyzed by countertop equipment that detects traces of explosives.

The TSA is testing walkthrough units that detect traces of explosives faster than the wand systems.

Document scanners that would detect explosives transferred to boarding passes are also being tested at the agency's laboratory.