Depends on the definition of "fire zone"
Following NEC and NFPA 30 there are definitions of some required "distances" that can be useful for some purposes.
Considering the exposure to fire heat there are several rules and formulas oriented to obtain a safety distance where heat exposure is limited to a safe value, which you can find on books,I reckon that the NFPA Journal had on article on this issue some years ago. There are also software that can model the effects of wind, the type of smoke, the height of flames to get more reasonable values.
Look also on FMGlobal data sheet 7-32 and 7-88 (flam liq. ops and tanks).