NFPA 58, the LP-Gas Code, uses the term "important building" when stating where an LP-Gas container may be placed. This term is not defined in the code. There is information in the LP-Gas Code Handbook in the commentary after section 6.4.1.1. Being commentary, it does not carry the weight of law, but it gives you insight into the intentions behind the rules.

The following information is provided to help determine which buildings are important. Inspectors in North Carolina will use these criteria when performing inspections.
A building is an important building if any of the following conditions are met.

• The building is a place where humans live or work.
• The building and/or its contents are expensive or valuable.
• The building is made of combustible material.
• The building contains combustible material.
• The building contains a source of ignition.
• The building presents a hindrance to emergency responders to apply water to an LP-Gas container.

The term "important building" is used in the 2017 edition of the LP-Gas Code in the following sections:

   6.3.2 ASME Containers Not Connected for Use
   6.4 Container Separation Requirements
   6.24.3 Installation of Direct-Fired Vaporizers
   6.24.4.3 Installation of Tank Heaters
   6.30 Alternate Provisions for Installation of ASME Containers
   8.4 Storage [of Cylinders] Outside of Buildings