A program meant to keep Americans safe from airborne threats could be grounded if the Department of Homeland Security can’t convince Congress that the next generation of technology will produce useable results.

Lawmakers last week questioned whether the BioWatch program—a network that collects airborne particles and conducts daily tests for pathogens—should attempt to move forward when previous efforts have garnered such tepid results, according to the Los Angeles Times.

“How can we proceed with procurement of a new system when we don't fully understand the capabilities of the current system?” the Times quotes Rep. Gus M. Bilirakis (R-Fla.) as asking at a joint subcommittee hearing on September 13. “Where is the cost-benefit analysis that proves this next-generation system would be a sufficient improvement over the existing system? Where is the analysis of alternatives?”

The nearly 10-year-old program first installed a series of air sensors in about 30 U.S. cities to check for threats such as anthrax or plague bacteria. Those sensors—which had to be collected and tested by hand with a 30- to 36-hour turnaround on results—were considered too cumbersome for early warning.

In 2007, a second generation of the sensors that could collect and transmit data hourly were installed in some locations. By 2009, that program was scrapped because of technical problems and DHS began plans for a third generation. These so-called labs-in-a-box would be able to collect and analyze particles and notify authorities of a threat almost immediately.

The department had hoped to fully deploy the third generation by this year, but according to the Los Angeles Times, field tests have shown that the prototypes have durability and sensitivity issues. The newspaper (one of the few mainstream news sources to report on the program’s recent challenges) published an article in July calling the system “the biodefender that cries wolf,” citing state health department officials frustrated with BioWatch false alarms. DHS Assistant Secretary for Health Affairs Alexander Garza has disputed those claims.

Even if the functionality of the current system is ignored, the financial aspects aren’t likely to be. Cost estimates for the program have grown from what was initially projected in 2011—from $2.1 to $5.7 billion—according to a Bloomberg article. Only about $800 million has been spent by the U.S. government so far, according to the article.

At least some of the cost increase can be attributed to poor resource management and DHS's failure to follow its own acquisition guidelines, according to a Government Accountability Office report released last week. The report recommended that DHS “reevaluate the mission need and alternatives and update associated performance, schedule, and cost information” before moving ahead with the third generation of BioWatch.

In the meantime, support for the program—or biosurveillance in general—could be waning. As an editorial in New Scientist points out, “Since the U.S. anthrax attacks of 2001 there has been no bioterrorism anywhere in the world. Unlike conventional explosives, germs pose a minuscule terror risk.”

That sentiment was also expressed by subcommittee member Rep. Bennie G. Thompson (D-Miss.) during the hearing. “We must understand that we are on Generation 3 because Generations 1 and 2 did not work,” he was quoted as saying in the Times. “It is time to reconsider the likelihood of the risk [of a biological attack] and adjust our priorities.”