You need space for the water and electric connections behind the washer and dryer, and enough space for the sliding door in front of them. I have had washers and dryers for over fifty years (several sets, of course) and never left either door open to "dry" the insides. No problem with mold or smell or mustiness.
If you have had that problem, there must be something wrong with your machine's emptying system.

Thank you Couzzjo for your question! The washer and dryer are set on tiles in case anything were to happen with the machines. If the homeowners would like to air the washer out, the door would be left open as in this photo for a short time. The pocket door is dually for hiding the noise and the washer/dryer from view.

Do you ever have problems with the pocket door vibrating and making noise from the vibration of washer and dryer?
Thanks

Devin Darnell,

The washer and dryer are on a different [tile] floor than the rest of the hallway which also helps lessen the noise. There is also enough space provided to eliminate any vibration that may occur, but the washer and dryer units are already pretty quiet.