Screening mail for biological agents
The U.S. Postal Service indicates that these steps are in place to check for pathogens in mail, like ricin, sent to Congress and federal agencies. After irradiation, mail is returned to delivery facilities.
Air samples checked for pathogens
Transported to irradiation facility in New Jersey
Mail is heated
Containers of mail and packages scanned
At the nation’s more than 200 mail-processing facilities, as envelopes travel along conveyor belts to be scanned and bar-coded, a machine about the size of an office copier takes periodic air samples to track for biological agents.
Once mail with federal addresses is sorted at a Washington facility, USPS trucks it to a New Jersey irradiation facility operated by Sterigenics, a company known for its medical sterilization equipment.
Federally addressed mail are heated to temperatures often exceeding 150 degrees.
Large containers holding first-class mail and packages are scanned by a high-energy electron beam or X-rays to kill potentially harmful biological agents, including anthrax.
NOTE: According to postal inspectors: Magazines, catalogues and such mail as credit card solicitations are not screened further because the USPS considers the senders trusted sources. Priority mail and express mail packages — which require return addresses and tracking numbers and must be dropped off in person or handed to a letter carrier — are not run through biological detection machines, because threat assessments have deemed such inspections unnecessary.
Positive results are from preliminary tests. Further analysis and confirmation can take 24 to 48 hours.