I am assuming that the oil company who supplies us would have to meet NFPA standards, wouldn't they?   There is probably 5000-10000 gallons in IBC's and other plastic containers in their warehouse.  The same applies to the herbicide distributor.  

I'm not advocating having fires and I do not take the threat of fire lightly, but this must not be so simple because I do not think using IBC's for combustible liquids is outside the realm of normal practice.