Ammonium nitrate

Ammonium nitrate is a hazardous chemical that has many grades and is used in fertiliser and explosives products because of its unique properties.

Find out more about its hazards and safe management.

Ammonium nitrate is an odourless material, which is usually granulated (if a fertiliser) and white in appearance. Crystalline ammonium nitrate is not usually found outside a laboratory.

Ammonium nitrate can be classified as both a:

• Class 5.1 Oxidising agent under the Australian Dangerous Goods (ADG) code
• hazardous chemical under the Globally Harmonised System (GHS).

It is a strong oxidizer and can react violently with other incompatible materials, so it is very important to store and handle ammonium nitrate correctly.

Similar names for ammonium nitrate include:

• nitric acid ammonium salt
• detapril
• nitropil.

The storage of liquid ammonium nitrate (UN 2426) or materials classified as Class 1 explosives (such as ammonium nitrate with more than 0.2 per cent combustible substances (UN 0222) is not covered here. Seek expert advice to deal with these materials.

What is it used for?

In Queensland approximately 99% of ammonium nitrate is used as an explosive in mining operations. The remainder is used for making fertiliser.

Security sensitive ammonium nitrate

Security sensitive ammonium nitrate (SSAN) is specifically covered by the Explosives Act 1999 and includes:

• ammonium nitrate
• ammonium nitrate emulsions
• ammonium nitrate mixtures containing greater than 45 per cent ammonium nitrate.

Solutions and ammonium nitrate products that are classified as class 1 explosives are excluded. SSAN may also include non-dangerous goods.

More information about ammonium nitrate, including siting and security requirements for security sensitive ammonium nitrate are available from Resources Safety and Health Queensland.

What are the hazards?

Stability and explosion

Ammonium nitrate is stable in solid, molten or in solution. However, it can become less resistant to detonation/initiation due to the presence of contaminants or on exposure to high temperatures (e.g. fire or radiant heat).

The following can cause ammonium nitrate to become less stable and at greater risk of detonation:

• exposure to contaminants including:
• chlorides
• metals such as chromium, copper, cobalt, and nickel
• a decrease in pH (increased acidity)
• if bubbles are permitted to form in molten ammonium nitrate or solutions of ammonium nitrate.

Once ammonium nitrate becomes molten (particularly if confined) the risk of an explosion increases. This risk increases dramatically if the pH of molten ammonium nitrate falls or if it comes into contact with oxidisable material for instance organics such as oil, diesel, paper, rag, or straw.

Ammonium nitrate may explode due to the following factors:

• exposure to strong shocks (e.g. from shock waves of nearby explosions
• exposure to high temperatures under confinement (e.g. in a closed pipe)
• a smaller detonation can trigger an explosion in larger quantities stored nearby.

Heat, fire and combustion

Ammonium nitrate does not burn. However, it will support and increase the rate of combustion in the presence of flammable or combustible materials even in the absence of oxygen.

When heated it will melt, decompose and release toxic gases including nitrogen oxides (NO_x) and ammonia gas (NH₃). When heated excessively (e.g. as in a fire) it can cause an explosion in an enclosed space and closed containers or vessels may rupture violently.

Physical properties

• Melting point: 170°C.
• Decomposition temperature: < 210°C.

Chemical properties

• Strong oxidiser that can react violently with other incompatible materials.
• Acidic: pH of 5.4.

Health effects

• Harmful if swallowed.
• Irritating to eyes, skin and respiratory tract.

Managing hazards and risks

After reviewing the safety data sheet and container label:

1. Identify the hazards from ammonium nitrate in the context of how the material is being stored and handled.
2. Conduct a risk assessment to determine the nature, likelihood and severity of any incidents that may result in harm to persons, property of the environment (e.g. fire, explosion or spillage).
3. Decide on and implement appropriate control measures to ensure that the risk to people, property and the environment is minimised as far as possible.

Training, information and supervision

The occupier of the premises must ensure people employed at the premises are trained in:

• safe work methods for handling ammonium nitrate
• hazardous properties of ammonium nitrate
• location and use of safety and personal protective equipment
• action to take in an emergency (e.g. spills, fire or explosion).

Workers need to be effectively supervised to ensure systems and procedures are followed.

Systems and procedures

Procedures should be documented to inform workers about how to store and handle ammonium nitrate safely. The systems should ensure that the risks identified in your risk assessment are effectively managed.

Following are some examples of appropriate procedures:

• How to clean up a spill.
• Segregating incompatible goods.
• Operating machinery.
• Lock up and security procedures.
• Inventory management and stock control.
• What to do in a theft, fire or other emergency.

Container disposal

When disposing of ammonium nitrate, consider the following:

• It is highly soluble in water and at low concentration can be fatal to livestock if it contaminates water courses.
• Burying ammonium nitrate residues with hot earth and organic material can result in a violent underground reaction and is not recommended.

Empty containers should be washed out with water (triple rinsed) before their disposal. Unless the containers are refilled with the same materials, the containers should be removed or fully destroyed.

Consult the manufacturer about the disposal of unwanted ammonium nitrate.

More information

More information on ammonium nitrate is available in the Australian Standard AS4326: The storage and handling of oxidizing agents.

Find out more about the requirements for ammonium storage structures.

Find out about specific requirements for storing and handling ammonium nitrate.