Fact 1 - one ceases to smell something that is there all the time at about the same level.
Fact 2 - adding more scent can let you then smell it again.. for a while.
Fact 3 - after some indeterminate period of this escalation, you will be able to stun an elephant at a hundred paces.
Now she's gone and I can breathe again. Glad she doesn't work in my area.