My CF center told us on day 1 to never use one, even the new expensive ones. They easily grow pseudamonas and you don't want that! However, my pediatrician recently said he disagrees and that I needed one when my son had a cold. I'm not gonna take the chance though. We did a steam filed bathroom with his therapy when he was sick. Not sure what's best for your whole house, but I woudn't take the risk