A method for self-cleaning of a photo-ionization detector for volatile gases

摘要

The PID includes an ultraviolet lamp for transmitting UV light through an optical window into an ionization chamber to ionize volatile gases. The UV lamp comprises a sealed envelope containing inert gases and a pair of driving electrodes disposed outside the sealed envelope to induce a glow discharge of the inert gases. An ion detector is disposed in the ionization chamber to detect the produced ions. During operation of the PID, the effectiveness decreases due to contamination formed in the ionization chamber. To remove the contamination, the pump is turned off while maintaining the transmission of the UV lamp. Thus the UV light creates an ozone discharge which accumulates in the ionization chamber. Ozone is a strong oxidant which etches and removes the contamination from the ionization chamber. <IMAGE>