"An envelope that tested positive for the deadly poison ricin was intercepted Tuesday afternoon at the U.S. Capitol's off-site mail facility in Washington, congressional and law enforcement sources tell CNN. Senate Majority Leader Harry Reid said he was told the letter was addressed to the office of Sen. Roger Wicker, R-Mississippi. After the envelope tested positive in a first routine test, it was retested two more times, each time coming up positive"
Envelope tests positive for ricin at Washington mail facility
When I worked for the USPS, they had installed extremely sensitive air sampling equipment over the high-speed mail-sorting machinery, that could detect anthrax spores if any escaped envelopes or packages containing it, and would immediately sound alarms, both visual and audible. Dunno if they could also detect ricin, but if not, most likely they soon will be after this incident.
Of course the detection equipment would not help a mail-carrier in his or her vehicle, if he or she happened to come in contact with, or breathe in the spores after collecting the tainted mail (or package) to take to his or her PO for eventual shipment to a mail processing facility. Postal management let us wear cheap paper-filter face-masks on the job, soon after the anthrax scare of '01, but they were already known to be completely useless in filtering out the microscopic spores.