In June 2005, the U.S. Environmental Protection Agency (EPA) finalized the Clean Air Mercury Rule (CAMR). As part of the rule, all coal-fired power plants were required to do continuous mercury measurements. Although CAMR has now been vacated by the courts, based on discussion with the EPA, it is expected that the mercury measurement requirements as written will be part of any future mercury regulations. This paper focuses on the process for certifying a continuous mercury monitor and conducting a relative accuracy test audit using EPA Method 30B. Based on the experience gained at the Energy & Environmental Research Center, a number of recommendations for conducting a RATA are provided. (C) 2009 Elsevier B.V. All rights reserved.