Fig.16 shows the variation of collection efficiency with collection voltage at different ion flow rates. Generally, an increase in collection voltage produced an increase in the ion collection efficiency of the collector for both negative and positive ions. It was shown that the ion collection efficiency of the collector increased to 100% at a collection voltage larger than 5 and ion flow rate of 1 L/min, for a collection voltage larger than 20 V the ion flow rate needed to be 3 L/min and for 40 V the ion flow rate of 5 L/min also gave 100% collection. This shows that the ion collector proved to be particularly useful in collecting positive and negative ions.