Sunday, January 27, 2013

AZF Accident

On 21 September 2001, just 10 days after the heinous terrorist attacks of 9/11 in USA, it was time for the people of Toulouse in South-West France to hear the noise of explosions but because of entirely different reasons. An explosion that would create a crater of a depth 20 to 30 m, with a 200 m diameter. 

View of the crater created after the explosion


The AZF factory in Toulouse was part of Great Parish, leading French producer of fertilizers, a group company TotalFinaElf. It was situated on a plot of 78 hectares, 5 kilometers from the city centre; the plant was built between the highway leading to Tarbes and the Garonne. Built in 1924, most of its installations dating from 1960.

The AZF plant produced mainly ammonium nitrate, ammonium nitrate-based fertilisers and other chemicals including chlorinated compounds.

On this cursed day, the AZF factory in Toulouse employed 470 people. About 80 people, also working permanently on the site, were used by nine external companies. The explosion occurred in a “downgraded ammonium nitrates” store which had off-spec ammonium nitrate storage.

In the coming sections we will see how this accident led to a series of policy changes in areas of risk management and specifications of ammonium nitrate based fertilizers.

The Accident Itself
Site of the disaster

Till date the cause of the explosion has not been pin-pointed. There have been various theories that have been hypothesized. The major ones are that it could be a human error, a terrorist attack, an underground explosion outside the AZF which acted as an initiator, electromagnetic disturbances in the EDF network. The case that went for prosecution considered this as a chemical accident where a chemical, which is a chlorine derivative ‘DCCNa’, was mistakenly stored in the hangar that had ammonium nitrate and these two chemical compounds reacted to lead to an explosive reaction.

Consequences of this Accident

The explosion unfortunately killed 31 people, including 21 working in the AZF factory. More than 4500 injured have been identified. 27 000 structures were destroyed property around the plant. Compensation of more than 2 Billion Euros has been paid since the accident.

Lessons from the accident

Even though the exact causes for the explosions have not been figured out but this accident left a big dent on the fertilizer industry and triggered a lot of policy changes in area of risk management.
The disasters at Toulouse reminded Europe that the control-based Seveso II directive (in particular its Safety Management System requirement) was not enough to prevent major a accidents turning into disasters.

Some of the major changes are:

1) The maximum content of nitrogenous fertilisers should very rapidly be limited to a maximum value of between 28 and 31.5% of nitrogen (80 to 90% of ammonium nitrate), which would reduce the risk of explosion and the risk of their use as explosives.

2) The Toulouse explosion showed the need to improve our knowledge of potential risks. The Toulouse disaster has created a strong awareness concerning the coexistence cities industries. To address these issues, the law of 30 July 2003 on risk prevention plans to develop “Technology Risk Prevention Plans" (PPRT). This law puts a long-term perspective on urban development around hazardous plants. It also gives local councillors a stake in the risk prevention decision making process, instituting Local Committees for Information and Dialogue (CLIC). Public opinion thus becomes involved in decision-making, the aim being to make choices more acceptable to local stakeholders.

3) The accident that occurred in Toulouse on the 21st of September should lead to a re-examination of the position of many factories that are situated in an urban environment. Based on the AZF Disaster the French Government has put new regulations in place from July 2003. These regulations concern new measures to improve the efficiency of future construction limitations and to deal with existing dangerous situations of urbanism around SEVESO sites.

4) To have the corresponding hazard studies brought up to date (taking into account the risks of the domino effect in production factories between ammonium nitrate stores and ammonia stores).

Sources :

2) Urban growth analysis within a high technological risk area, Case of azf factory explosion in toulouse (france), Casita project:
4) Press release:Explosion at the azf factory in toulouse: The general inspectorate for the environment


  1. En attendant des commentaires:

  2. Is this accident the same than the one that happened a few days ago in Texas?

  3. Jonathan,
    it's to early to say... Come back in a year or 2...
    NB: IMHO, it looks more like a burst of an ammonia tank/sphere (BLEVE), as this plant mainly stored liquid ammonia

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  5. How come people don't know why that accident took place? It is very important to know the cause because unless you know the reason you may let it repeat again. There are many kinds of chemical reactions also which don't look like explosion but have very bad impact on the population.


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