your chickens are breathing that in all the time. How are their lungs?
don't your chickens scratch in the coop? How far are their nostrils from it?
as it does when a chicken scratches. Doesn't the deep litter method rely on chickens scratching in it?
I poo pick every day so bad air issues don't arise.
If you need to wear a mask or other face covering when you're in the place you keep your chickens, spare a thought for your chickens having to breathe it in all the time. Small wonder there are so many posts about respiratory issues here...