of the barrier 22 the installation length of the barrier 22 can be selectively sized to correspond to a first dimension of the condenser unit 24 for example the widths that can be seen in fig4 and 5 of the condenser unit 24 by cutting transverse to the length of the barrier 22 in preferred embodiments the width of the barrier 22 transverse to its length can be pre sized to correspond to the dimension of the condenser unit 24 transverse to its first dimension for example the particular height of the condenser unit 24 visible in fig4 fig6 illustrates a method by which the contamination barrier 22 may be attached to the condenser units 24 of fig4 and 5 fig6 is a cross sectional view showing one of the parallel edges 38 of the contamination barrier 22 and a clip 26 that preferably extends the entire width of an opening 36 of the condenser unit 24 through which the tube and fin assemblies 12 not shown are exposed to incoming air the clip 26 is mounted to a wall 34 of the condenser unit 24 that defines the opening 36 of the condenser unit 24 the clip 26 can be manufactured from various materials for example extruded.