Only seen it in one China airport, and think it should be the standard everywhere.
We have all seen/experienced the "swab" for explosives, but it is random and arbitrary.
One airport in china - after the initial screening, before the "official" screening - EVERYONE GETS SWABBED, but, with the same swab. After which, you are put in a "holding pen" with about 20-30 people. Then they check the swab, which of course always comes up clean. Then all 30 people are released.
While the swab check is being performed on the group in holding pen A, people are still being swabbed, but put into an holding pen B.
The net is - everyone gets screened, and it adds maybe 30 seconds to the process.
Possibly effective and near zero cost in time or inconvenience to the traveller.
Maybe that explains why TSA doesn't do it.
