More than 200 machines once touted as a high-tech response to keep the skies safe have been removed from service.

The 207 Explosive Trace Detection portals purchased by the Transportation Security Administration are now sitting in a government warehouse.

The $150,000 machines were designed to blast passengers with a puff of air and then analyze the particles it shook loose searching for any sign of explosive materials.

"When they worked well, they were outstanding," said Larry Wansley, the former head of security for American Airlines.

But the units rarely worked.

"With the testing that was done in the labs, they really couldn't simulate an airport environment, and that was the joker in the deck," Wansley said.

The TSA would not agree to an interview, but a spokesperson confirmed that dirt, debris and humidity commonly found in most airports rendered the units useless.

The agency acknowledges that it spent nearly $30 million to purchase and maintain the so-called "puffer machines." But less then half of the units were ever deployed.

In 2008, the TSA started to quietly remove the 94 units that were deployed across the country. The last remaining machines were removed from service last year.

Critics say the TSA wasted $30 million in a rush to put untested technology into service instead of doing the necessary research.

"When you're talking about spending millions of dollars in taxpayer money, you have to wonder why these things have not been tried and tested and trued up in some form or fashion," said Katrina Pierson, co-founder of Tea Party Review Magazine.

"There is so much government waste," Wansley said. "This is just another example of the $500 crescent wrench -- same thing."