Make-Up Air Unit Filtration

If anyone can help, please. We are having issues with our make-up air unit, and our maintenance guy is pointing fingers at the filters. We are also looking at adding another one and we want to make sure we are doing it right. 

Through all of my reading, I have determined that we need at least a Merv 11, if not more, filter. This system is blowing outside air back into our oven room where finished, RTE product is stored open overnight. 

I would be happy to use a lesser filter if it is food safety is not a concern, they are certainly more affordable and I could stop having this conversation with maintenance. 

Does anyone have experience with MAU that can help steer me in either direction? I am not all that familiar with HVAC. 

Thanks in advance!

They function similarly to a heating/cooling system on your home

I think given that it's only pulling in outside ambient air a Merv 11 filter seems sufficient to me

Assuming your FG have a relatively short shelf life anyway, so any risk of yeast/mold wouldn't be impacted by the MUA