My boyfriend used to be addicted to oxycotton.. I'd like to know what they smell like after they are smoked?

He used to be highly addicted to oxy's... and I catch him still every now and then....but each time I say something he will deny it. He used to smoke them from tin foil.. Id like to know if oxy's have a specific smell to them... because each time his mouth has a certain scent ( Which I always assume is Oxy's..) It'll be after he brushed his teeth and have a gum in his mouth. Im just curious if it's a way to cover the scent/taste from me. Cause I'm assuming he wouldn't want me to find out. It's so upsetting to me when he does it... HELP!