andyjm said:
			
		
	
	
		
		
			Measuring equipment is far, far more sensitive that any human sense.
		
		
	 
That's true of sight and hearing, but not of smell.
Did you not watch the recent docs on TV about Quantum modelling? Very intersting explanation about how we smell things, and why we wosmetimes confuse two different chemicals, yet they smell the same. It's more complicated than simply th chemical lock and key model that we thought was the case. Ergo, our sense of smell is pretty flawed, and you could argue that the simple fact that we can easily consuse odour that it's way beind the "science". A dog or a cat have way way more sensitive olfactory response, so measuring equipment can probably detect down to molecular level, we can't.