Storage building for LP and filling of tanks

[Wally's World]

What are the classification boundries for a cold storage building that houses LP gas in less than 100 lb tanks and also has an area inside where these tanks are filled from a bulk tank that is 35 feet away. The building has rectangular 12"x15" holes at the top and bottom around the buildings 10 foot high walls. The walls are made of precast concrete. The holes are for natural ventilation and are on 3 sides of the building with the 4th side having 8 foot garage doors. I realize the inside has at minimum a Class 1 Division 2 classification and the area around the tank filling is a Class 1 Division 1 clasification. My main concern is if the area around the outside of the building has a classification and if it does where are the boundries?

 

[Smart $]

Most likely the area immediately outside the building nearest the bottom vent holes will be classified. LP gas is heavier than air. Can't say exactly how far or high. The classified areas should be documented. Check with owners and AHJ.