On June 1, 2006, the EPA issued final corrections to a rule issued in August 2000, revising the monitoring requirements in Performance Specification 1 (PS-1). The rule is intended to correct certain errors in the rule. Specifically, the revisions updated requirements for source owners and operators who must install and use continuous stack or duct opacity monitoring equipment. The revisions also updated design and performance validation requirements for continuous opacity monitoring system (COMS) equipment in PS-1. The final rule established differences between gaseous continuous emissions monitoring systems and COMS. Apparently, the final rule contained a minor error in wording and the action issued on June 1 is intended to correct the error. The rule was immediately effective.