40 CFR § 60.2972
How must I monitor opacity for air curtain incinerators that burn only wood waste, clean lumber, and yard waste?
June 9, 2020
(a) Use Method 9 of appendix A of this part to determine compliance with the opacity limitation.
(b) Conduct an initial test for opacity as specified in §60.8.
(c) After the initial test for opacity, conduct annual tests no more than 12 months following the date of your previous test.
(d) If the air curtain incinerator has been out of operation for more than 12 months following the date of the previous test, then you must conduct a test for opacity upon startup of the unit.