If one Fan (Reference) "blower" removes heat from the back, away from the other components. The disadvantages are cooling and fan volume which is noisy. If Dual Fans is almost silent and performs much better. The downside is they throw all the heat into and potentially affect the heat of other components. You will then need a case of high airflow to avoid heat on the chassis. It's the best way to add outdoor equipment that can help cool or reach normal temperatures.