My Maxx Air only expels air, as it's uni-directional. I wish it had a reversible motor, as it is sometimes useful to be able to draw cooler or warmer air from outside, in.
Mike. Comments are anecdotal or personal opinions, and worth what you paid for them.
2018 (2017 Sprinter Cab Chassis) Navion24V + 2016 Wrangler JKU (sold @ ????)
2016 Sunstar 26HE, V10, 3V, 6 Speed (sold @ 4600 miles)
2002 Roadtrek C190P (sold @ 315,000kms)