"what is TATP made of that he could have stepped in to trigger the false positive?"
Almost all explosives are nitrates. If you've been to a farm and stepped in manure or artificial fertilizer, you'll set off any decent chemical sniffer looking for nitrates.
What are nitrates? Cheaper than day rates. :)
Almost all explosives are nitrates. If you've been to a farm and stepped in manure or artificial fertilizer, you'll set off any decent chemical sniffer looking for nitrates.
Or step into any local Mosque and walk away with nitrates.
TATP is made from acetone and hydrogen peroxide, if I understand correctly. It is cheap to make but unstable, and can blow up accidentally (like on a bench outside a stadium in Oklahoma, for example.)