We have developed a new gas purifier for ArF excimer lasers that can remove all the impurities from degraded ArF excimer laser gas. We found that cooled activated charcoal at temperatures below −50 °C effectively removes CF4, which is the preponderant impurity generated in ArF excimer laser gas mixtures. We also demonstrated that the new gas purifier can regenerate the ArF excimer laser gas up to its initial purity level after about 1×109shots of operation. ©1996 American Institute of Physics.