Great point. You don't source from the same spot you source combustion air - you run a separate fresh air intake. This system has HEPA, fresh air intake and hum

Great point. You don't source from the same spot you source combustion air - you run a separate fresh air intake. This system has HEPA, fresh air intake and humidity control packaged/integrated together well. The fresh air wouldn't come from a garage or crawl space, but from the outdoors via a dedicated (small) duct.