I brought this up before in other threads, but this bears repeating here.

What was passed by congress was a law that required the Secretary of DHS to “give a high priority to developing, testing, improving and deploying, at airport screening checkpoints, equipment that detects nonmetallic, chemical, biological, and radiological weapons, and explosives, in all forms, on individuals and in their personal property.” 49 U.S.C. § 44925(a).

The current equipment in use does not detect "nonmetallic, chemical, biological, and radiological weapons, and explosives". They image.