Dust in the Hen House

Extension has a post on poultry housing options.  From personal experience I can testify to the dusty conditions in a hen house (what they categorize as a barn).

Air quality is often poorer in alternative housing systems, and this can affect health and hygiene, which is relevant not only for hen welfare but also for food safety.
The large amount of litter and the greater bird movement in alternative systems result in greater concentrations of bacteria and fungi in the air and in greater dust concentrations compared with conventional and furnished cage systems. Greater dust concentrations have been associated with more serious pulmonary lesions, typical of chronic bronchitis, in cage-free birds (Michel and Huonnic, 2003).

As you might expect they've reservations about cage systems.  Whether or not they properly weigh the tradeoffs I won't judge, but there are tradeoffs.