“Unobstructed” as applied to exhaust stacks for purposes of modeling means that:

1. (a) There is no impediment to vertical flow from the exhaust stack; and
2. (b) The exhaust stack extends at least 2 feet higher than any roofline within 10 feet of the exhaust stack exit, measured horizontally.

Source. #10549, eff 4-4-14; ); ss by #13105, eff 9-25-20 (formerly Env-A 101.210) (see Revision Note #4 at chapter heading for Env-A 100)