The Amerithrax case of 2001, in which letters harboring Anthrax spores were delivered to media outlets and a pair of US Senators' offices, killed five people and sickened another 17. In the wake of these attacks, the US Postal Service (USPS) installed a system of electronic noses in mail processing facilities around the country designed to sniff out the deadly bacteria before someone else does.
Much like the IRS, the USPS is not constrained by the Fourth Amendment when it comes to the screening of mail. According to Postal Code § 233.11 Mail reasonably suspected of being dangerous to persons or property:
When the Chief Postal Inspector determines that there is a credible threat that certain mail may contain a bomb, explosives, or other material that would endanger life or property, including firearms which are not mailable under Section C024 of the Domestic Mail Manual, the Chief Postal Inspector may, without a search warrant or the sender's or addressee's consent, authorize the screening of such mail by any means capable of identifying explosives, nonmailable firearms, or other dangerous contents in the mails.
Development of the Biological Detection System began in 2002 when the USPS outlined the basic functions such a system would need, based on the agency's consultations with Joint Projects Office (JPO) and the SBCCOM (US Army Soldier Biological Chemical Command). No existing system was capable of what the USPS needed, so the postal service set about developing one that did. Or at least Northrop Grumman did, in coordination Smiths Detection. Northrop adapted aspects of more than 20 systems already in use by the US military for biological warfare tests to the specific needs of the USPS. The US Army Research Institute of Infectious Disease (USARIID) Navy Medical Research Center, NIST, Dept of Agriculture, and John Hopkins University all helped vet the system's performance before its initial test run in a Baltimore-area mail processing center in late 2002.
As mail travels through the Advanced Facer Caneler System, it travels under a small hood that draws in ambient air, transmitting it to an aerosol collector in the BDS cabinet. This collector concentrates the suspect particles in a sterile water solution and then automatically transfers it, along with a reagent to the PCR (polymerase chain reaction) unit. The PCR duplicates the biological sample's DNA and compares the result against a known sequences of Anthrax. If the test returns positive, the site controller is notified and the offending mail can be recovered for further inspection All this takes less than an hour and is performed on-site.
Since entering service in 2003, more than a thousand BSD units have been installed in mail centers around the country.
As of 2009, the BSDs had screened screened tens of billions of packages and completed a total of eight million tests—all without a false positive. That's an impressive figure, even if Anthrax is no longer the most fashionable pathogen.