Before there were full-body scanners, there were puffers.

The Transportation Security Administration spent about $30 million on devices that puffed air on travelers to "sniff" them out for explosives residue. Those machines ended up in warehouses, removed from airports, abandoned as impractical.

The massive push to fix airport security in the United States after the attacks of Sept. 11, 2001, led to a gold rush in technology contracts for an industry that mushroomed almost overnight. Since it was founded in 2001, the TSA has spent roughly $14 billion in more than 20,900 transactions with dozens of contractors.

In addition to beefing up the fleets of X-ray machines and traditional security systems at airports nationwide, about $8 billion also paid for ambitious new technologies. The agency has spent about $800 million on devices to screen bags and passenger items, including shoes, bottled liquids, casts and prostheses. For next year, it wants more than $1.3 billion for airport screening technologies.

But lawmakers, auditors and national security experts question whether the government is too quick to embrace technology as a solution for basic security problems and whether the TSA has been too eager to write checks for unproven products.

"We always want the best, the latest and greatest technology against terrorists, but that's not necessarily the smartest way to spend your money and your efforts," said Kip Hawley, who served as the head of the TSA from 2005 until last year. "We see a technology that looks promising, and the temptation is to run to deploy it before we fully understand how it integrates with the multiple layers we already have in place like using a watch list, training officers at every checkpoint to look for suspicious behavior and using some pat-downs."

Some say the fact that the United States hasn't had another 9/11-level terrorist attack shows that the investment was money well spent.

But government auditors have faulted the TSA and its parent agency, the Department of Homeland Security, for failing to properly test and evaluate technology before spending money on it.

The puffer machines, for example, were an early TSA attempt at improving electronic screening in airport security lines. Designed to dislodge explosive particles by shooting air blasts at passengers, the detectors turned out to be unreliable and expensive to operate. But they were deployed in many airports before the TSA had fully tested them, according to the Government Accountability Office.

The puffers were "deployed even though TSA officials were aware that tests conducted during 2004 and 2005 on earlier [puffer] models suggested they did not demonstrate reliable performance in an airport environment," according to a GAO report from October 2009.

TSA officials told the GAO that they had deployed the puffers to "respond quickly to the threat posed by a suicide bomber" after incidents on Russian airliners in 2004.

The agency stopped buying and deploying the puffer machines to airports in June 2006. The GAO said in its October 2009 report that 116 puffers were in storage. A TSA spokesman said the agency had "since disposed of" the machines or transferred them to other agencies.