Not certain of what you are working on, but I suspect it is a Norlake walk in cooler. The guard over the fan is a fan guard or air deflector. Some have air directional fins to send the air flow to still areas of the cooler. They are part of the evaporator and are supplied by the evaporator vender. There will be a plate with the make and model on the evaporator. Usually on the end or rear corner.near the electrical connections. Most common out their is Heatcraft, Bohn, Larken and Trenton.