A gas burner unit for a cooktop having a spreader positioned above the top surface of the cooktop. The spreader has a plurality of gas outlets. A venturi is in fluid communication with the gas outlets. An orifice holder secures a gas orifice in position in a main body of the orifice holder and has a plurality of protrusions extending upwardly and defining a plurality of upwardly directed primary air inlets. The plurality of primary air inlets are in fluid communication with the main body of the orifice holder, and the main body is in fluid communication with the venturi. A general primary air inlet allows ambient air from outside the cooktop to enter the area below the cooktop, and the main body of the orifice holder includes openings allowing fluid communication between the area below the cooktop and the main body of the orifice holder.