Hello.. I’m switching from my old wood stove to a England pellet. I’m venting via 4” liner out of an existing flu from the first floor (approx 13’). My stove requires an outside air kit. The issue I’m running into is the total run of a fresh air tube would be about 12’, is that okay? I was planning on using a piece of exhaust pipe as a union because I can only find a tube at 10’ total length. Is there any clearance to combustibles for fresh air intake tube? Thanks.