Yes, he had mentioned the fox urine solution!
And then...he'd added the "mock up" of his very own solution (pictured in his blog). Silly man! (He has a good sense of humor!)

I am quite sure I can locate the "fox stuff" locally, as there are many retail places in this region with stuff like that! Yet, it will definitely not be my first attempt at a solution!

Thanks for the link to "liquid fence." I will take a look at it!

I cannot imagine using ammonia in your home/ductwork.
I hope it does not come to that for you!

Hope you can stay cool enough until all air conditioning, in your castle and in your chariot, are running well.