Abstract
The influence of electrostatic field of a video display terminal (VDT) upon the ion concentration of the surrounding air was measured. A three-day continuous measurement was made in a room with mechanical ventilation at the distance of 0.4 m from the VDT. The electrostatic field of the VDT reduced the concentrations of light air ions. When the VDT was unenergized the ion concentration varied between 55-2600 ions/cm3 for positive and 125-2100 ions/cm3 for negative ions. When the VDT was energized the corresponding levels were 35-100 ions/cm3 for positive and 30-90 ions/cm3 for the negative ones. Measurements of the ion current showed that switching the VDT on decreased the ion concentration very rapidly.