EPA has adopted standardized training and certification procedures in 40 CFR Chapter I, Part 60, Appendix A, Method 9. Smoke school involves basic education and certification using these procedures. For certification, black and white smoke is generated at different opacities for a total of 50 separate visible emission readings. Opacities must be within a certain percentage of accuracy, for both types of smoke, for certification to be obtained. Certification expires after six months.