Figure 10 shows a schematic representation of current generated by electrons crossing the gap from the cathode to the anode. The current increases until a time Te and decreases afterwards. The rise is due to increasing arrival of electrons at the anode. The steep drop at Te is due to the arrival of the head of the electron avalanche at the anode. After time Te, the electron current does not drop to zero and a decreasing ramp is present until a time T. The decreasing ramp is caused by electrons that arrive after the avalanche head. These delayed electrons are those that have been detached from unstable ions in the gap. Due to the time required for detachment, their arrival at the anode is later than that of the free electrons. This secondary ramp is referred to in the literature as an after-current [9]. With increasing humidity a reduction in the after-current has been reported. This is caused by a decreased number of electrons that have detached in the gap [9]. The reduction in the number of detached electrons is attributed to conversion reactions that have incorporated these electrons into non-detaching ions. The electron detachment processes are independent of the electric field. The amount of conversion reactions on the other hand, is a function of the partial pressure of water vapor. The times involved in detachment and conversion processes are different, with the detachment time being virtually constant. Conversion reaction times are a function of humidity and are shortened substantially for humid air when compared to the value at less than 1% RH [9]. It has been reported that at humidity level of 65% RH at 20°C, the number of free electrons and unstable negative ions are reduced by a factor of 5.8 and 2.7, respectively, when