Yes, but only one SUNON 12V/0,5W low noise Fan with 40mm x 40mm at the Side. This Fan cools the Hard-Drive(s) and the Mainboard of the NVR. Without Fan the temperature will increase critically.
The NVR42xx-4ks2 has no CPU Fan like the old NVR42xx models.
Maybe the NVR42xx-4KS will work without Fan if you use ist vertically in combination with low Power consumption Harddrives (ex: 2,5"), since the natural air convection will reduce heat inside.
The attached Photo shows a new NVR42xx-4ks2 without POE and Hard drives. Look at this tiny CPU (SOC)! Do you really want it to work with up to 32Cams?
Remark: I would recommend a NVR52xx-4ks2 because of better Performance (and faster CPU). The old NVR4232-4k was a crab with a lousy CPU cooler and many Performance problems! The NVR52xx-4ks2 has the same Fan configuration as the NVR42xx-4ks2.