Coffee Break Training: Fire Protection Series: Hazardous Materials: Indoor Parking and Servicing of Liquefied Petroleum-Gas Transport Vehicles [open pdf - 481KB]
"When LP-Gas [Liquefied Petroleum Gas] transport vehicles are parked or serviced in separate structures indoors by the owner/operator, the building must meet the construction requirements of National Fire Protection Association 58, 'Liquefied Petroleum Gas Code'. A 'separate' structure is one that is not attached to any other buildings or structures on the site."
Coffee Break Training - Fire Protection Series No. FP-2013-14
United States Fire Administration: http://www.usfa.fema.gov/