40 CFR §62.15090

1. (a)If you close your municipal waste combustion unit but will reopen it prior to the applicable final compliance date in table 1 of this subpart, you must meet the increments of progress specified in § 62.15040.
2. (b)If you close your municipal waste combustion unit but restart it after the applicable final compliance date in table 1 of this subpart, you must complete the emission control retrofit and meet the emission limits and good combustion practices on the date your municipal waste combustion unit restarts operation.