2012 International Fire Code, Section 307.4.3 - Portable Outdoor Fireplaces (the kind you can purchase commercially) are allowed for use within the District and shall be used in accordance with the manufacturer's instructions. They shall not be used within 15 feet of a structure or combustible material. Screening shall be constructed of woven or welded wire screening of 12 USA standard gage wire having openings not exceeding½ inch in order to prevent embers from escaping.
2012 International Fire Code, Section 307.3 - Extinguishment Authority: TMFPD has the authority to extinguish, or require the extinguishment of, any open burning or use of a portable outdoor appliance when it creates a hazardous situation.
2012 International Fire Code, Section 3071.1 - Prohibited Open Burning: Open burning shall be prohibited when atmospheric conditions or local circumstances make such fires hazardous. Check here for Red Flag conditions in your area.