The terrorists who set off suicide bombs during the Paris attacks used an explosive, triacetone triperoxide (TATP), that is relatively easy to synthesize at home using chemicals sold in pharmacies and hardware stores.
It's also relatively easy to sniff out, say chemists developing sensors that can detect TATP and help to prevent similar attacks. Suicide bombers all over the world have used TATP, from Palestinians in the West Bank to the "shoe bomber" Richard Reid.
The secret to the new sensor, writes Alex Berezow in the BBC, is vapor pressure, how readily a compound converts from the solid to the gaseous state. Because TATP has a relatively high vapour pressure, it easily becomes a gas, so a suicide bomber wearing a vest containing TATP should emit enough gaseous particles to set off the alarm on a sensor.
Multiple labs are working on sensors than can detect TATP and other chemicals common in terrorist attacks, Berezow notes.