...
Crystalline ammonium nitrate is a major form of nitrogen fertilizer. Lesser amounts are used to make explosives and nitrous oxide. It is also used as an anesthetic. Ammonium nitrate may enter the environment from industrial or municipal waste treatment plant discharges, agricultural runoff, or spills.
When heated, ammonium nitrate may explode, as it is a highly reactive chemical, posing a dangerous explosion hazard. It decomposes on heating or on burning, producing toxic fumes (nitrogen oxides). The substance is a strong oxidant and reacts with combustible and reducing materials.
Ammonium nitrate can affect you when breathed in and by passing through your skin. Exposure may irritate the skin, eyes, nose, throat, and lungs. Overexposure can cause nausea and vomiting, headaches, weakness, faintness, and collapse. Severe overexposure may lower the ability of the blood to carry oxygen. This can result in a bluish color to skin and lips, headaches, dizziness, collapse, and even death.
Scope
OSHA’s regulations for the storage of ammonium nitrate apply to all persons storing, having, or keeping ammonium nitrate, and the owner or lessee of any building, premises, or structure in which ammonium nitrate is stored in quantities of 1,000 pounds or more.
OSHA has not established an occupational exposure limit for ammonium nitrate. This does not mean it is not harmful. Safe work practices should always be followed.
Regulatory citations
- 29 CFR 1910.109 — Explosives and blasting agents
Key definitions
- Ammonium nitrate: A synthetic, inorganic compound that is produced in large quantities. It is an odorless, colorless to white solid that is found in various forms such as crystals, flakes, and grains.
- Blasting agent: Any material or mixture, consisting of a fuel and oxidizer, intended for blasting, not otherwise classified as an explosive and in which none of the ingredients are classified as an explosive, provided that the finished product, as mixed and packaged for use or shipment, cannot be detonated by means of a No. 8 test blasting cap when unconfined.
- Explosive: Any chemical compound, mixture, or device, the primary or common purpose of which is to function by explosion, i.e., with substantially instantaneous release of gas and heat, unless such compound, mixture, or device is otherwise specifically classified by the U.S. Department of Transportation.
- Explosive-actuated power devices: Any tool or special mechanized device which is actuated by explosives, but not including propellant-actuated power devices. Examples of explosive-actuated power devices are jet tappers and jet perforators.
Summary of requirements
All persons storing, having, or keeping ammonium nitrate, and the owner or lessee of any building, premises, or structure in which ammonium nitrate is stored in quantities of 1,000 pounds or more, must comply with the following general requirements:
- Sensitive mixtures. The storage of ammonium nitrate and ammonium nitrate mixtures that are more sensitive than allowed by the “Definition of Test Procedures for Ammonium Nitrate Fertilizer” is prohibited.
- Large quantity storage. Approval of large quantity storage shall be subject to due consideration of the fire and explosion hazards, including exposure to toxic vapors from burning or decomposing ammonium nitrate.
- Storage buildings. Storage buildings shall not have basements unless the basements are open on at least one side. Storage buildings shall not be over one story in height.
- Ventilation. Storage buildings shall have adequate ventilation or be of a construction that will be self-ventilating in the event of fire.
- Walls and roofing. The wall on the exposed side of a storage building within 50 feet of a combustible building, forest, piles of combustible materials and similar exposure hazards shall be of fire-resistive construction. In lieu of the fire-resistive wall, other suitable means of exposure protection such as a free-standing wall may be used. The roof coverings shall be Class C or better, as defined in the Manual on Roof Coverings, NFPA 203M-1970, which is incorporated by reference as specified in 1910.6.
- Flooring. All flooring in storage and handling areas, shall be of noncombustible material or protected against impregnation by ammonium nitrate and shall be without open drains, traps, tunnels, pits, or pockets into which any molten ammonium nitrate could flow and be confined in the event of fire.
- Water seepage. Buildings and structures shall be dry and free from water seepage through the roof, walls, and floors.
- Electrical installations. Electrical installations must conform to the requirements of Subpart S of Part 1910, for ordinary locations, and must be designed to minimize damage from corrosion. In areas where lightning storms are prevalent, lightning protection must be provided.
- Fire control. Not more than 2,500 tons (2270 tonnes) of bagged ammonium nitrate shall be stored in a building or structure not equipped with an automatic sprinkler system. Sprinkler systems must be of the approved type and installed in accordance with 1910.159. Suitable fire control devices such as small hoses or portable fire extinguishers must be provided throughout the warehouse and in the loading and unloading areas, and must comply with the requirements in 1910.157 and 1910.158. Water supplies and fire hydrants must be available in accordance with recognized good practices.
The regulations at 1910.109 also contain specific requirements for:
- Storage of ammonium nitrate in bags, drums, or other containers — 1910.109(i)(3)
- Storage of bulk ammonium nitrate — 1910.109(i)(4)
- Contaminants — 1910.109(i)(5)