http://ohioline.osu.edu/vme-fact/0018.html
This link describes the use of sevin dust.
I wouldn't dust the yard, myself.
Also, here is a link for sevin dust egg withdrawal time:
https://www.backyardchickens.com/forum/viewtopic.php?id=491429&p=2
If you are just doing maintenance, keep in mind that a lot of people use DE (which you also shouldn't breathe, as it is fossil shell flour) on the chickens and in the coop. I do this several times a year on the chickens.
But when I get an active infestation AND seasonally just to be safe (because I repeatedly get mites in my flock from the songbirds) I treat with poultry dust (sevin and permethrin).
If your chickens inhale a lot of the dust they will wheeze. Happened to me when I was careless. The wheezing was gone in 24 hours. Heck, even I felt like wheezing. It was like swimming in the dust inside the coop. So wear a mask, long sleeves, take shower afterward, etc.
I always dust my girls outside now because of that experience. I take an old sock and tie off the top (you can use stocking too) to use it as a powder puff.
The stuff is toxic, but works well at killing bugs. Just use precautions and I wouldn't broadcast it everywhere.
Alternatively, you can make a dust bath for them with it in it so they put it on themselves (mix with sand).