Homemade, Cheap and Dangerous

'Nobody Ever Stops Me'

The risky side of TATP is that it is highly unstable. A spark or light friction can detonate the explosive, making it extraordinarily difficult to handle. Experts and police said there have been numerous cases in which suspected terrorists -- as well as foolhardy amateur chemists -- have set off accidental explosions, resulting in death or severe injuries.

"You need to concentrate the chemicals," said Hans J. Michels, a professor of chemical engineering at Imperial College in London. "It's a filthy job and it's dangerous, but it can be done."

Despite the dangers, al-Qaeda cells have used peroxide-based explosives in more than a dozen plots in the past decade, including the July 7 and 21, 2005, London incidents, as well as attacks in Casablanca, Istanbul and the Indonesian island of Bali, according to counterterrorism officials. Danish police also discovered TATP in September during the arrest of seven terrorism suspects in Odense.

In crystalline form, TATP looks like powdered sugar and is difficult to detect in airports; security officials need to examine an exposed surface with a swab kit or other tester to determine its presence.

"TATP and peroxide-based explosives are concern number one for the aviation industry," said Ehud Keinan, a chemistry professor at Technion-Israel Institute of Technology and a leading researcher on the substance. "It will take some time before we are protected. Right now, we are not."

Reached by telephone in Paris, where he was scheduled to give a lecture about TATP on Wednesday at an international conference, Keinan said he often carries a small sample of the volatile compound in his carry-on luggage when he flies -- just to test airport security. "Nobody ever stops me," he said.

When asked if it might be dangerous to sit next to him on a plane, he said, "If you know how to take care of it, it's okay. If you don't know what you're doing, you're in trouble."

U.S. Homeland Security officials have said terrorism suspects arrested last August in Britain on charges that they were plotting to blow up several transatlantic airliners might have been planning to smuggle on board TATP or a related compound, HMTD, hexamethylene triperoxide diamine. Experts said it would take as little as one or two quarts of those explosives to down a large plane.

TATP was discovered in the late 19th century but was deemed to have no industrial or commercial applications because it was so unstable. Researchers generally ignored the substance until 1980, when Palestinian fighters used it for the first time in a bomb in Israel.

Palestinian bombers have used it ever since. TATP was used for the first time in an attack in Europe in July 1994, when Palestinians exploded a car bomb outside the Israeli Embassy in London.

U.S. and European counterterrorism investigators paid limited attention to the explosive until the July 2005 bombings in London. Afterward, the New York City Police Department built an exact replica of the apartment in Leeds, England, that the July 7 conspirators allegedly used to manufacture their backpack bombs.

Hugh O'Rourke, deputy inspector of the NYPD counterterrorism division, said the police department wanted to show beat officers what a kitchen-counter TATP production line would look like. He said it is easy to mistake the white powder and its cooking tools -- such as pool cleaners, large tubs or commercial-size fans -- for a common drug lab.

"Patrol cops see a lot of white powder, think it's crack, and want to touch it and package it," which could easily result in an explosion, he said. "We don't want them doing that."