Fresh air intake

lowercanada

I've been asked to help a local non-profit ( a peer -mentoring mental health organization) get ready for winter by surveying their several (7 in one 2-story ~50'x20' building !!) furnaces and replace filters as required. I've done a fair amount of minor work for them, so it's not my first time in the building. The building has been re-muddled many times…there are 3 different ceilings in some places, each layer lower than the one above and the in-between spaces filled with live, dead and somewhere in between "stuff".

Two of the units, both ceiling hung, one above the drop ceiling, one exposed, included short duct runs** from outdoors directly into the return air trunks. These were NOT part of a modern HRV system, and there were no dampers in the outdoor intakes. Thankfully, one of these systems was removed as part of a recent remodel. The remaining one —-it's actually not a furnace but is an air handler for a roof mounted heat pump, part of an SDHV HVAC system—-is mounted above a drop ceiling, no drop down access door and a very tight fit to the grid, and popping panels sucks (sucks as in, the fit is so tight that somewhere in the past someone substituted acrylic diffuser panels because you can flex those out). On this unit, the short outside air intake is flex-ducted from the thru-wall exterior grill to the air handler return plenum, just ahead of the filter rack. But, the flex duct has no slack, and absolutely prevents getting a correctly sized, unbent filter into the filter rack. The building owners (the org. owns the building) have had a few different HVAC service co.s over the years I've known them, and let's just say the techs haven't been the A-team….I've seen bent filters, doubled filters, cut filters…

Which brings me to why I'm posting….Given that these fresh air intakes are NOT combustion air, and NOT part of a modern HRV system —this is NOT an airtight building—is there any reason I shouldn't just remove the fresh air intake? Was it code at some point? An early attempt at air quality management? I'd like to be able to actually get the right filter installed..right now there's a 14x25 kitty-cornered into the 16x25 (I think) rack because that's all the last guy up there could get in.

** I've been told that not long after the exposed ceiling hung unit was installed in an attempt to get heat to that section of the building, the fresh air duct run was also a squirrel run…guess the installer didn't have an intake with a grill on the truck that day…