For property that is held for internal use or transferred to another Federal agency, it is the fair value of the property less a valuation allowance for any liens or third party claims.
You can deduct liens and third party claims from the fair value of the property in order to determine a certain figure pertaining to the property held for internal use.
In addition to recognizing the complex atmospheric chemistry relevant for some pollutants, air quality modelers also must deal with uncertainties associated with variable meteorology and the spatial and temporal distribution of emissions.