The House Homeland Security Subcommittee on Emerging Threats, Cybersecurity, and Science and Technology approved on March 29, 2007, legislation (H.R. 1680) that would give DHS the authority to regulate the sale and purchase of ammonium nitrate to prevent its use by terrorists. The Secure Handling of Ammonium Nitrate Act would require DHS to establish a threshold percentage for ammonium nitrate in a substance within 90 days of the bill's enactment. Under H.R. 1680, owners of ammonium nitrate facilities and purchasers of the substance would be required to register with DHS. Owners of facilities engaged in selling or transferring ammonium nitrate would have to maintain for three years a record of each sale or transfer of ownership. DHS would have to establish a process for the periodic inspection and auditing of these records. Those who are licensed to produce, sell, or purchase ammonium nitrate exclusively for use as an explosive material would be exempt from the bill's provisions.