Once again, thanks for the wisdom of more experienced inspectors. I recently encountered a jump duct from master bedroom to a hallway, terminating inside the return air duct in the hallway. I understand it’s purpose, my question is; should it be filtered on both ends?
Does not need to be filtered at all. In fact, a filter would likely hinder the intended air pressure balance.
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Thanks Brian, I was thinking 2 filters was definitely too many, and wondered if even one was too much.
Absolutely not……the one filter is plenty. The jump return is simply to balance the air flow.
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I disagree. It does need a filter. Is the hallway where the main filter is installed? Or is the filter at the air handler?
If this is the filter location, then yes, it does need a filter on the jumper also. (just one end)
Because that return will also pull unfiltered air from the master, bypassing the hallway filter.
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Ha? So what would happen when the bedroom door is left open?
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Thats why I was trying to ask him if the filter goes in that large return, or if the filter is at the air handler. If that IS where the filter belongs, then the jumper would also need a filter in it, because it pulls air from the bedroom, and enters AFTER the main filter.
If the filter is at the air handler, than no filters are necessary here.
You have not answered my question.
Does not matter where it was or was not… what matters is where it should be. If it’s at the wrong location, as a home inspector, you should be able to point that out.
Thats why I was trying to get the OP to tell us if the filter was at the air handler or not… That would determine if that jumper should also have a filter.
In regards to your question, it wouldnt matter if the door was open or not. The placement of that jumper would be sucking air from the hallway AND from the bedroom at the same time, no matter what. If the jumper were installed in the wall or ceiling like normal, then it wouldnt be pulling air POST filter. It would just be serving to equalize.
HA, but now I just realized this is 4 months old 
The OP is in Texas. Not always but typically here for quite a few years they have been placing the filter at the unit. They will have multiple returns (i.e. some times in each bedroom) so they use the one filter at the unit.
What is interesting in this case is the return is an operable one (it can be opened/it is hinged) and appears capable of holding a 1" filter. I can’t recall one in some time where they used a more expensive return (not much but every dollar counts) when the filter is at the unit.
Another interesting item is look how clean those grills are on both returns! 
I’ll still “jump” back in even after 4 months. No, no filter at the air handler, there was a return plenum in the hallway, with a 1" filter behind a grill, AND a 1" filter inside the plenum at the end of the jump duct, as well as a 1" filter at the other end of the jump duct, located in the master bedroom. Grills were that clean, only because this was a new construction home, never occupied. Thanks again for all the input!