I would imagine, during pilgrim season, most albergues are sprayed each day when people leave and it's probably part of the cleaning.
So if you're trying to avoid chemicals completely, I think you're probably out of luck.
When I spray a bed (on those rare occasions I stay in albergues these days), I use a pump spray and I spray a few inches above my OWN bed.
I do my best to be sure nobody else is in the room, or at least near my bed.
But the sprays I use are heavy and fall directly on my bed, not into the air around me.
Since Falcon convinced me to use permethrin on the outside of my pack and my sleeping bag, I don't spray at all.
I am on disability for Multiple Chemical Sensitivities and I can not tolerate most chemicals.
But the permethrin, once dry, has no odor and I have no reaction to it because my body never touches it.
It is on the OUTSIDE of my sleeping bag, not on any part that touches me.
I also do as my blog says, and I carefully watch for signs of bedbugs.
If I find signs, I don't stay in that albergue, and I've never had anyone refuse a request for money back.
There is simply no way you are going to be able to control what people wear or spray in albergues. There is also no way you are going to make them polite if they have not been trained to be polite.
If you are bothered THAT much by fragrances or chemicals (as I am) or by rude pilgrims, you would be smart to find yourself a walking partner (or 2-3) who is/are willing to share a private room with you.
Often, you can rent a double or a quad for as little or even less than you will pay for a dorm bed.
That way, you can have better control of your environment.
Except for that, you can complain until God comes, and it isn't going to change the fact that when you are sharing space with a group of people somebody is probably going to do something you don't like. I gripe all the time about headlamps in my eyes and rustling plastic bags, but it hasn't stopped their use on the Way
Being able to accept that and live in a different way for 6 weeks or NOT being able to accept it can make or break your Camino.
::shrug::