October 8,
2018 1308 
When crime lab chemists handle evidence that contains illegal drugs, trace amounts of those drugs are inevitably released into the laboratory environment. When chemists scoop a bit of powder to test it, for instance, microscopic particles can become airborne and later settle on nearby surfaces. Particles can also be spread by touch. To some degree, this is an unavoidable byproduct of the testing process, and it can result in detectable background levels of drugs in the lab.
Now, scientists at the National Institute of Standards and Technology (NIST) and the Maryland State Police Forensic Sciences Division have developed a protocol for measuring those levels and used their new protocol at three forensic chemistry labs. Their findings were published in Forensic Chemistry.