Many fan manufacturers and inspector like rain caps on the discharge side of the grease exhaust fans to keep much of the rain out of the fan bowl. This can reduce the effluent in the small catch pans. However, the down side that we can clearly see in this pictures is that the rain caps actually act as an impact point and often divert the grease back down onto the roof in other areas including into the fan motors and surrounding rooftop areas. We can see the impact on the first picture of the the rain cap and the heavy diverted grease on top of the fan and fan motor housing. A robust listed rooftop containment system under the fan with the rain cap removed will in most cases eliminate this issue. Also, I am not a fan of cage fans with heavy grease loads as we call them grease slingers. Best is an upblast style fan with lower RPM's (Requiring larger fans) that impact the grease plume into the surrounding sides of the fan before it exits the system. With cage fans, there is a gap that is never impacted thus allowing larger particles of grease to discharge onto the rooftop areas around the fan. This is only an issue with high or medium grease loads.
