It is possible, and in many cases likely, that a facility may have the option of choosing from a range of configuration types under which to to report emissions. However, it is also possible that only one configuration type would be a valid selection. The reporter should review 40 CFR 98.36 to determine what configuration types are appropriate. If more than one configuration is valid for a group of units, the reporter may freely decide which configuration type to use. For example, if a group of units combusts natural gas fed by a common pipe, and all units are smaller than 250 mmBtu/hr, the reporter could select to report the group of units under the common pipe or aggregation of units configuration types.