All activities shall only be conducted in buildings classified as fireproof by Chapter 31, Article II, Building Code, and Chapter 31, Article III, Residential Code, of the City of Havre de Grace, and the Fire Prevention Code and other applicable codes as established by the Department of Inspections, Licenses and Permits of Harford County, Maryland, as well as the International Property Maintenance Code, in accordance with § 31-1, Article I, of the Code of the City of Havre de Grace. Operations shall be conducted in such a manner and with such precautions as to prevent fire and explosion hazards. All raw materials and finished products shall be stored within an entirely closed building. Liquids may be stored in underground tanks that have been permitted and approved by the appropriate regulatory agency.