How do you used lasers to detect dangerous chemicals?

Question: How do you used lasers to detect dangerous chemicals?
- Keywords:
  chemical,
  dangerous,
  detect,
  laser
Asked by Perfect Particles to Luke, Philip on 16 Mar 2015. This question was also asked by 352terb32, rebel.
- Philip Moriarty answered on 16 Mar 2015:
  
  This is really Luke’s area – I’m certainly not an expert on this topic! — but one way of doing it is to use the laser light to detect the tiny vibrations of the molecules making up the chemical. There’s a technique known as Raman spectroscopy which detects those vibrations and gives you a “fingerprint” of the chemical that you can use to detect it.
  
  …but I suspect that Luke does something entirely different!

Question: How do you used lasers to detect dangerous chemicals?