Closets: Venting closets becomes necessary when components are installed the closet where ventilation is limited. Heat in a closet will accumulate very quickly and potentially cause heat-related problems.
Rooms: Rooms where a significant amount of equipment is installed can be 5+ degrees warmer than other rooms in a house. This is especially troubling if this is a home theater or other primary area in the house where the desire may actually be to keep the room cooler, not warmer than the rest of the house.
HiFlo Vent System. This system was specifically designed to quietly and effectively cool rooms and closets. It includes everything needed including a Temperature Controller and Power Supply. This product is intended to vent from room to room or closet to room. The ideal situation is to vent from the closet or room to a larger or more common area in the house where the warmer air will mix and be re-circulated through the HVAC system.
Return Vent System. This system is primarily intended for new construction projects but it can also be retrofit if there is accessibility to the room or closet through an attic. This system is intended to be connected to the home's HVAC system or it can also be connected to a remote duct for venting from the one room or closet to a room or hallway to promote better circulation in the home.
It is important to NEVER vent air out of the home. The only exception are bathrooms and kitchen vents as that air is considered 'undesireable' where air that is simply heated by components should be recirculated through the house. HVAC systems are designed to recirculate air and in the summer, warm air from the house is simply reprocessed into cooler air. When venting out of the home, that air is replaced by air from either the attic or outside which can be hot, humid, dusty, smelly, etc. It takes more time and energy for the HVAC to 'condition' that air than air simply heated by components. In addition, in the winter, why not utilize the warmer air thoughout the rest of the house as well?