Question: I have a process that runs from 7 a.m. to 7 p.m daily. I want to use emission factors to specify when AERMOD should calculate output concentrations. In BEEST, I select the HROFDY emission rate flag. Which hours need to be enabled for this time period?

Answer: You will need to put the emission factor 1 into the enabled hours and 0 into the other hours. As for the hours, different regulatory agencies have different guidelines for which hour should be the first hour for a modeling period. You should ask your regulatory agency, as it could be either hour 7 or hour 8 in your case.