The Department of Homeland Security’s new biological threat detection and warning program faces limitations with the key systems and technologies it hopes to use although Biological Detection for the 21st Century (BD21) program officials are taking actions to mitigate risks to the program, the Government Accountability Office (GAO) says in a new report.

The BD21 program is in the early stages of the acquisition cycle and is aimed at replacing the current BioWatch system, which essentially consists of hundreds of aerosol collectors deployed in around 30 major urban centers in the U.S. that constantly sample the environment for the presence of biological threats. The samples are collected daily and transported to local laboratories for analysis to determine whether a deadly biological agent is present, a process that can take 12 to 36 hours from the initial collection to result.

The goal of the BD21 program is to eventually shorten the time from sample collection to result to between four and nine hours through the use of advanced, networked sensors and software.

However, GAO said some of the technologies planned for BD21 still need work. For example, the report the machine learning-based anomaly detection algorithms that the DHS Countering Weapons of Mass Destruction Office plans to use for BD21 haven’t been developed or used for biodetection in the planned indoor and outdoor settings.

Currently, the initial plans for BD21 are to continue manual sample collection just like with BioWatch to allow the anomaly detection algorithm to be tested alongside the current detection protocol that is based on laboratory analysis of the air sample.

Initially, the anomaly detection algorithm would analyze data from a single sensor but eventually the program hopes to use the algorithm to process data from sensors deployed to multiple locations, thereby enhancing the accuracy of the detection protocol, GAO says.

Another technology limitation that GAO cites is the trigger technology, which are the aerosol sensors that monitor the air for biological material.

“According to officials from the BD21 program office and DoD, the trigger technologies currently available are known to produce frequent false positives and false negatives,” GAO says. The report cites Defense Department use of triggers for an early warning bio-threat detection system that suffer increased false alarm rates from “common environmental material such as pollen, soil, and diesel exhaust.”