For international transportation by vessel or by air, the requirements of the International Maritime Dangerous Goods Code (IMDG) or the International Civil Aviation Organization Technical Instructions for the Safe Transport of Dangerous Goods by Air (ICAO TI) apply. In instances where transportation of hazardous materials in accordance with these standards is not possible or practicable due to extreme urgency, or when other forms of transportation are inappropriate, or full compliance with the standards is contrary to the public interest, exemptions to these standards may be granted. Additionally, if either of these standards provide provisions for approval by the competent authority, then the Office of Hazardous Materials Safety serves as the United States competent authority for granting such approvals.