P404 Air Sampling of Asbestos and MMMF and Requirements for a Certificate of Reoccupation Following Clearance of Asbestos is the industry standard qualification for those whose work involves air sampling and clearance testing, such as asbestos analysts. In addition to holding the qualification, they are required to undertake and provide evidence of annual refresher training. RP404 Refresher is a new course, specifically designed to meet this requirement. RP404 Refresher enables candidates to revise and update their knowledge on air sampling and clearance testing techniques, and to receive a certificate of course completion by passing a written examination, which covers both the theory and practice of air sampling and clearance testing.