40 CFR §60.2966

1. (a)Yes, if you are subject to this subpart, you are required to apply for and obtain a title V operating permit unless you meet the relevant requirements for an exemption specified in § 60.2887, or unless your unit is an air curtain incinerator exempt under paragraph (b) of this section.
2. (b)If you own or operate an air curtain incinerator that burns only wood waste; clean lumber; yard waste; or a mixture of wood waste, clean lumber, and/or yard waste and that is subject only to the requirements in §§ 60.2970 through 60.2973, you are exempt from the obligation to obtain a title V operating permit, provided that your air curtain incinerator is not otherwise required to obtain a title V operating permit.