Fan trays move the heat out of enclosures that equipment moves in: rack-mount fan panels that pull air through a cabinet, top-mount trays that exhaust a closed enclosure, and the replacement fan assemblies that keep switches, chassis, and cabinets inside their thermal limits. Heat is the quiet killer of electronics; a fan tray is the cheap insurance against it.
Match the tray to the enclosure first - rack-mount trays are sized in rack units, top-mount trays to a specific cabinet family - and place it where the airflow actually helps, completing the enclosure's front-to-back or bottom-to-top path rather than fighting it. Replacement fan trays for network chassis are model-specific and worth stocking as spares, since a chassis that loses cooling will throttle or shut down on its own schedule, not the maintenance window's. Sealed and filtered options exist for dusty rooms. COLAMCO quotes fan trays and enclosure cooling for business, government, and education equipment rooms.