What are recommended clearances for a portable electrical generator?
The general advice seems to be 


3 feet (1 meter) from buildings, equipment, and combustible materials.
10 feet away from bystanders, children, and pets.


But the only way to know for sure, is to read the manufacturer's documentation for your specific unit.



This service manual says "Keep the generator at least 1 meter (3 feet) away, including overhead, from any structure..."


  


This owner's manual says "Operate generator at least 3 feet (1 meter) away from buildings and other equipment."


  


This operator's manual says "Keep the generator a minimum of 3 feet away from all types of combustible material."


  


and also says "Keep all bystanders, children, and pets at least 10 feet away."