Many of the monitoring tools - intended to detect guns, explosives, and nuclear and biological weapons - were bought during the blitz in security spending after the attacks of Sept. 11, 2001.
In its effort to create a virtual shield around America, the Department of Homeland Security now plans to spend billions of dollars more. Although some changes are being made because of technology that has emerged in the last couple of years, many of them are planned because devices currently in use have done little to improve the nation's security, according to a review of agency documents and interviews with federal officials and outside experts.
"Everyone was standing in line with their silver bullets to make us more secure after Sept. 11," said Randall J. Larsen, a retired Air Force colonel and former government adviser on scientific issues. "We bought a lot of stuff off the shelf that wasn't effective."
Among the problems:
¶ Radiation monitors at ports and borders that cannot differentiate between radiation emitted by a nuclear bomb and naturally occurring radiation from everyday material like cat litter or ceramic tile.
¶ Air-monitoring equipment in major cities that is only marginally effective because not enough detectors were deployed and were sometimes not properly calibrated or installed. They also do not produce results for up to 36 hours - long after a biological attack would potentially infect thousands of people.
¶ Passenger-screening equipment at airports that auditors have found is no more likely than before federal screeners took over to detect whether someone is trying to carry a weapon or a bomb aboard a plane.
¶ Postal Service machines that test only a small percentage of mail and look for anthrax but no other biological agents.
Federal officials say they bought the best available equipment. They acknowledge that it might not have been cutting-edge technology but said that to speed installation they bought only devices that were readily available instead of trying to buy promising technology that was not yet in production.
The department says it has created a layered defense that would not be compromised by the failure of a single device. Even if the monitoring is less than ideal, officials say, it is still a deterrent.
"The nation is more secure in the deployment and use of these technologies versus having no technologies in place at all," said Brian Roehrkasse, a spokesman for the Department of Homeland Security.
Every piece of equipment provides some level of additional security, said Christopher Y. Milowic, a customs official whose office oversees screening at ports and borders. "It is not the ultimate capacity," he said. "But it reduces risk."
Some critics say that even though federal agencies were pressed to move quickly by Congress and the administration, they made some poor choices. In some cases, agencies did not seek competitive bids or consider cheaper, better alternatives. And not all the devices were tested to see how well they worked in the environments where they would be used.
"After 9/11, we had to show how committed we were by spending hugely greater amounts of money than ever before, as rapidly as possible," said Representative Christopher Cox, a California Republican who is the chairman of the Homeland Security Committee. "That brought us what we might expect, which is some expensive mistakes. This has been the difficult learning curve of the new discipline known as homeland security."
Radiation at Seaports
One after another, trucks stuffed with cargo like olives from Spain, birdseed from Ethiopia, olive oil from France and carpets from India line up at the Port Newark Container Terminal, approaching what looks like an E-ZPass toll gate.
In minutes, they will fan out across the nation. But first, they pass through the gate, called a radiation portal monitor, which sounds an alarm if it detects a nuclear weapon or radioactive material that could be used to make a "dirty bomb," a crude nuclear device that causes damage by widely spreading low levels of radiation.
Heralded as "highly sophisticated" when they were introduced, the devices have proven to be hardly that.
The portal-monitor technology has been used for decades by the scrap metal industry. Customs officials at Newark have nicknamed the devices "dumb sensors," because they cannot discern the source of the radiation. That means benign items that naturally emit radioactivity - including cat litter, ceramic tile, granite, porcelain toilets, even bananas - can set off the monitors.
Alarms occurred so frequently when the monitors were first installed that customs officials turned down their sensitivity. But that increased the risk that a real threat, like the highly enriched uranium used in nuclear bombs, could go undetected because it emits only a small amount of radiation or perhaps none if it is intentionally shielded.
"It was certainly a compromise in terms of absolute capacity to detect threats," said Mr. Milowic, the customs official.
The port's follow-up system, handheld devices that are supposed to determine what set off an alarm, is also seriously flawed. Tests conducted in 2003 by Los Alamos National Laboratory found that the handheld machines, designed to be used in labs, produced a false positive or a false negative more than half the time. The machines were the least reliable in identifying the most dangerous materials, the tests showed.
The weaknesses of the devices were apparent in Newark one recent morning. A truck, whose records said it was carrying brakes from Germany, triggered the portal alarm, but the backup device could not identify the radiation source. Without being inspected, the truck was sent on its way to Ohio.
"We agree it is not perfect," said Rich O'Brien, a customs supervisor in Newark. But he said his agency needed to move urgently to improve security after the 2001 attacks. "The politics stare you in the face, and you got to put something out there."
At airports, similar shortcomings in technology have caused problems.
The Transportation Security Administration bought 1,344 machines costing more than $1 million each to search for explosives in checked bags by examining the density of objects inside. But innocuous items as varied as Yorkshire pudding and shampoo bottles, which happen to have a density similar to certain explosives, can set off the machines, causing false alarms for 15 percent to 30 percent of all luggage, an agency official said. The frequent alarms require airports across the country to have extra screeners to examine these bags.
Quick Action After 9/11
Because the machines were installed under tight timetables imposed by Congress, they were squeezed into airport lobbies instead of integrated into baggage conveyor systems. That slowed the screening process - the machines could handle far fewer bags per hour - and pushed up labor costs by hundreds of millions of dollars a year. At busy times, bags are sometimes loaded onto planes without being properly examined, according to several current and former screeners.
"It is very discouraging," said a screener who worked at Portland International Airport until last year, but who asked not to be named because he still is a federal employee. "People are just taking your bags and putting them on the airplane."
Equipment to screen passengers and carry-on baggage - including nearly 5,000 new metal detectors, X-ray machines and devices that can detect traces of explosives - can be unreliable. A handgun might slip through because screeners rely on two-dimensional X-ray machines, rather than newer, three-dimensional models, for example. The National Academy of Sciences recently described the trace detection devices as having "limited effectiveness and significant vulnerabilities."
As a result, the likelihood of detecting a hidden weapon or bomb has not significantly changed since the government took over airport screening operations in 2002, according to the inspector general at the Department of Homeland Security. Transportation security officials acknowledge that they cannot improve performance without new technology, but they dispute suggestions that no progress has been made.
"We have created a much more formidable deterrent," said Mark O. Hatfield Jr., a spokesman for the Transportation Security Administration. "Do we have an absolute barrier? No."
Counting machinery and personnel, aviation screening has cost more than $15 billion since 2001, a price that Representative John L. Mica, Republican of Florida, says has hardly been worthwhile.
"Congress is the one that mandated this," Mr. Mica said. "But we should have done more research and development on the technology and put this in gradually."
Concerns Despite Reliability
Some screening equipment has performed reliably. Machines that test mail at the United States Postal Service's major processing centers have not had a single false alarm after more than a year, officials said. But the monitors detect only anthrax, which sickened postal workers in 2001. And only about 20 percent of mail is tested - mostly letters dropped into blue post boxes, because they are considered the most likely route for a biological attack.
In about 30 major cities, equipment used to test air is also very precise: there have been more than 1.5 million tests without a single false positive. But only about 10 monitors were placed in most cities, and they were often miles apart, according to the inspector general of the Environmental Protection Agency. Detecting a biological attack, particularly one aimed at a specific building or area, would require perhaps thousands of monitors in a big city.
In addition, as contractors hurried to install the devices before the start of the war with Iraq - the Bush administration feared that Saddam Hussein might use biological weapons on American cities - they were often placed too low or too high to collect satisfactory samples, the inspector general noted. The monitors use filters that must be collected manually every day before they can be analyzed hours later at a lab.
"It was an expedient attempt to solve a problem," said Philip J. Wyatt, a physicist and expert on biological weapons monitoring equipment. "What they got is ineffective, wasteful and expensive to maintain."
Homeland security officials say that they have already moved to address some of the initial problems, and that they are convinced that the monitoring is valuable because it could allow them to recognize an attack about a day sooner than if they learned about it through victims' falling ill.
At the Nevada Test Site, an outdoor laboratory that is larger than Rhode Island, the next generation of monitoring devices is being tested.
In preparing to spend billions of dollars more on equipment, the Department of Homeland Security is moving carefully. In Nevada, contractors are being paid to build prototypes of radiation detection devices that are more sensitive and selective. Only those getting passing grades will move on to a second competition in the New York port.
Similar competitions are under way elsewhere to evaluate new air-monitoring equipment and airport screening devices. That approach contrasts with how the federal government typically went about trying to shore up the nation's defenses after the 2001 attacks. Government agencies often turned to their most familiar contractors, including Northrop Grumman, Boeing and SAIC, a technology giant based in San Diego. The agencies bought devices from those companies, at times without competitive bidding or comprehensive testing.
Documents prepared by customs officials in an effort to purchase container inspection equipment show that they were so intent on buying an SAIC product, even though a competitor had introduced a virtually identical version that was less expensive, that they placed the manufacturer's brand name in the requests. The agency has bought more than 100 of the machines at $1 million each. But the machines often cannot identify the contents of ship containers, because many everyday items, including frozen foods, are too dense for the gamma ray technology to penetrate.
The federal government will likely need to spend as much as $7 billion more on screening equipment in coming years, according to government estimates.
"One department charged with coordinating efforts and setting standards will result in far better and more efficient technologies to secure the homeland," said Mr. Roehrkasse, the Department of Homeland Security spokesman.
Some experts believe that this high-priced push for improvements is necessary, saying the war against terrorism may require the same sort of spending on new weapons and defenses as the cold war did.
"You are in a game where you are continually upgrading and you will be forever," said Thomas S. Hartwick, a physicist who evaluates aviation-screening equipment.
But given the inevitable imperfection of technology and the vast expanse the government is trying to secure, some warn of putting too much confidence in machines.
"Technology does not substitute for strategy," said James Jay Carafano, senior fellow for homeland security at the Heritage Foundation, a conservative think tank. "It's always easier for terrorists to change tactics than it is for us to throw up defenses to counter them. The best strategy to deal with terrorists is to find them and get them."
By ERIC LIPTON
Matthew L. Wald contributed reporting for this article.