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Safeguard OSH Solutions - Thomson Reuters

Safeguard OSH Solutions - Thomson Reuters

Safeguard Magazine

Perils of proximity

SUZANNE BROADBENT says the massive explosion at a Texas fertilizer plant is a reminder to us all to check how our hazardous substances are stored.

Most readers will recall the fertilizer plant explosion in Texas back in April, which killed 14 people and injured around 200. Houses were flattened and large buildings severely damaged, including a nursing home. The explosion left a crater nearly 30m wide, and it has been estimated that insured losses will reach US$100m.

The explosion in Texas was not the only bad news that month in the United States. Only three days earlier the explosions at the Boston marathon had killed three people and shocked the nation. Despite the higher death toll and the huge size of the explosion, the media focus has been on Boston, probably because it is seen as an intentional act by individuals who intended to cause harm.

However, in terms of impact and ongoing consequences, the Texas fertilizer plant explosion was of arguably greater significance. But what caused it?

A definitive answer must wait until various ongoing investigations are concluded, but it is possible to outline some general facts and to explore some probabilities. The site stored a lot of ammonium nitrate – including at least 30 tons in wooden bins inside a wooden warehouse that lacked any fire protection. A small fire in the warehouse turned into a small explosion, which triggered a large explosion. Storage of large quantities of ammonia, combustible feed and other flammable items contributed to the impact. Additional storage of over 100 tons of ammonium nitrate did not explode.

(There have been media reports that the original fire may have been intentionally started. These theories include the initiation of the explosion by a paramedic later charged with possessing bomb making materials, terrorist activities, and even a missile or rocket. However it is quite likely the initial fire was started by an electrical fault or a golf cart battery.)

Although the cause of the initial fire is not certain, the direct cause of the resulting explosion is clear – improper storage and handling of ammonium nitrate.

Looking further at the apparent systemic or root causes, they sound very familiar, and could be summarised as:

Poor communication, information and understanding of the hazards of the chemical.
Company avoidance of costs relating to compliance – including preparation of a risk management plan that claimed the chemicals stored on site did not pose any risk of fire or explosion (worst case scenario: a 10-minute release of gas, not harmful to humans).
A self-classification process that enabled the company to classify the site as “retail” and therefore avoid more thorough and regular inspection and review of their risk management plan.
Location of the site – close to schools, hospitals, residential housing.
Insufficient monitoring and enforcement (although the site had been prosecuted several times before).
Legal requirements “patchwork” – different requirements from different agencies with complexity, overlaps and holes. Fire/emergency, safety, environmental, and chemical requirements were handled separately, with insufficient communication between agencies.
Political pressure (in Texas) to be seen as industry-friendly. Including specific pressure from fertilizer industry groups for more lax safety regulations, resulting in weakening of regulatory requirements.

There have been other major explosions linked to the storage of ammonium nitrate:

  • • 
    2001 explosion in France killing 31 people and injuring more than 2000.
  • • 
    2004 explosion of cargo train in North Korea, killing at least 160 people.
  • • 
    1947 Texas City shipboard explosion that killed at least 581 people.

Could it happen here? Of course it could. After all, most of the seven preliminary causes identified above have a lot of similarity to findings following Pike River.

Ammonium Nitrate

Ammonium nitrate (NH4;NO3) is used as a nitrogen fertilizer. It is an oxidizer that reacts energetically with organic materials and can detonate when heated strongly. It is also used in the explosives industry (but note that it is not considered explosive by itself).

Ammonium nitrate is classified by New Zealand’s Environmental Protection Agency as: 5.1.1C, 6.1E (oral), 6.4A, 9.1D. This means that that it is considered an oxidizer, harmful by ingestion, irritating to the eyes and harmful to the aquatic environment. For transport it is UN1942 Class 5.1 PGIII.

As a transferred substance (100%), controls include test certification (>1000kg if closed packages, >100 kg if open), approved handlers (>1000 kg), emergency planning (>5000 kg). The regulatory controls are comprehensive and primarily relate to ensuring safe storage and separation from ignition sources and incompatible substances.

If ammonium nitrate is used or stored in New Zealand, it comes under the transferred substance, although mixtures may come under HSR002569 (fertilizers) if it is considered that they are not oxidizing.

Bill Birch

A recent EPA review of 400 sites revealed four out of every five sites were not compliant with HSNO.

This kind of unacceptable performance can result in a major incident – risking life, property and our environment.

Nearly 30 years ago the ICI warehouse fire resulted from a chemical reaction involving a Class 5.1 Oxidising substance. Fortunately, nobody was killed; however this incident, still cited as New Zealand’s major chemical incident, triggered a government investigation which resulted in the Hazardous Substances and New Organisms (HSNO) Act 1996.

A key requirement of our world class chemical management legislation is the correct segregation and storage of incompatible substances. This year’s tragedy in the town of West in Texas graphically illustrates the consequences of not safely managing Class 5.1 substances.

It appears ammonium nitrate, stored in a warehouse accessible to the public, caught fire, resulting in a major explosion which devastated the neighbouring township. Caught in the blast were emergency responders, rest home residents and local shop keepers. Two schools and many business premises were within the blast zone.

The preliminary investigation indicates the Class 5.1 ammonium nitrate was not correctly segregated from other substances. The wooden storage facility lacked appropriate fire protection and did not comply with state voluntary chemical facility performance standards.

Ammonium nitrate is used throughout New Zealand as a fertilizer as well as being a component of explosive mixtures (Ammonium Nitrate Fuel Oil) used extensively in the mining industry.

The poor level of HSNO compliance revealed by the EPA survey provides little confidence a similar event arising from the improper segregation and storage of oxidisers could not occur here.

Hazard information is contained in the safety data sheet (SDS) for ammonium nitrate. The SDS section 10 headed Stability and Reactivity clearly identifies the safe handling requirements covering reactivity, chemical stability, probability of hazardous reactions, conditions to avoid, incompatible materials and hazardous decomposition products. Even a handful of ammonium nitrate can trigger a reaction.

Workplace health and safety regulations require employees handling chemicals to be properly trained and equipped to safely carry out their task. The HSNO Controls specify an Approved Handler for ammonium nitrate, together with a location test certificate requiring an emergency response plan, site signage and secondary containment.

HSNO Code of Practice 16-1 Storage of Hazardous Substances prescribes the chemicals which can and cannot be stored together, while HSNO Code 36-1 Preparing for a Chemical Emergency describes the requirements of a comprehensive site emergency response plan.

While everyone is responsible for ensuring they handle chemicals safely, the appointed HSNO Person in Charge can provide correct handling advice and oversee compliance.

The Texas ammonium nitrate incident occurred in a facility we would all recognize as a farm supply depot similar to hundreds scattered throughout New Zealand, many in urban locations.

Compliance with workplace health and safety, including safe chemical management, is everybody’s business. Have you recently reviewed and rehearsed your site emergency response plan?

BILL BIRCH is technical manager with Responsible Care New Zealand, which can supply HSNO Codes 16-1 (wall chart) and 36-1 (hard copy or CD).

Simonne Moses

Surprisingly, the size of the business doesn’t appear to make much difference when it comes to hazardous substance storage – it depends more on the level of knowledge of hazardous substances within the organisation.

The most critical area I’ve encountered where knowledge appears to be lacking is with flammable vapours and electrical equipment. The concept of electrical equipment sparking and igniting flammable vapours is, in general, poorly understood.

Poorer performers tend to be those businesses where hazardous substances are not used as part of the core business. Quantities are generally low and may not trigger HSNO certification limits, but the substances can be stored haphazardly all around the site. Incompatible substances stored together, substances in unlabelled containers, substances in food containers, storing flammables next to sources of ignition, and not disposing of old substances are some of the more common issues.

I’ve come across quite a number of dangerous hazardous substance storage situations, including:

  • • 
    placing non-electrically-rated burglar alarms in a flammable liquid store to prevent theft;
  • • 
    flammable and oxidising gas cylinders placed under stairways that are evacuation routes;
  • • 
    flammable liquid cabinets right next to fire exits; and drums of corrosives and flammables stored on their sides on drum trolleys, fitted with dispensing nozzles which are dripping, with a small bucket draped over the nozzle to catch the drips.

One of the most dangerous instances was a company using tanks of flammable printing ink for labelling. There were several tanks each of more than 1000 litres located in a shed outside the main factory but within half a metre of the factory wall. The walls of the shed and the factory were not fire rated. The ink tanks had dip points to check the volumes. The dip points were being left open so flammable vapours were present. The ink was being heated to facilitate it being piped through to the factory, and the heating unit, within the ink storage shed, had a pilot flame. There could have been multiple fatalities if an explosion had occurred, not to mention total destruction of the business.

What action was taken? In the first instance the dip points were closed and the heating unit turned off, extinguishing the pilot light. Later on the heating unit was completely removed. The walls of the storage shed were concreted to give at least a four hour fire rating. Staff were trained and supervised to ensure dip points were kept closed when not in use.

SIMONNE MOSES is a health and safety consultant who specialises in hazardous substances.

Mike Nankivell

Hazardous substance storage is on the improve overall, though this depends on the client’s attitude and approach to compliance. That is, are they “do it if pushed”, or “just-in-timers”, or do they have a genuine desire to achieve a safe workplace and have (or are keen to adopt) a best practice safety culture? Our goal is to gently ease them into the latter group and by doing so help them raise the bar in relation to hazardous substance (and HSNO) compliance. Do it once, do it right.

For a dangerous storage example, dried-out Picric Acid in a laboratory is right up there in respect to perspiration level. When dried out the salts formed are a highly shock-sensitive explosive. The stuff used to be found even in high school laboratories! (Thankfully the substance isn’t as common now and has definitely gone from schools.)

What to do? Don’t handle the stuff. Leave it where it is and isolate the room or building. Contact NZ Defence Force’s civilian explosives inspector (via nearest police) who will assess if the product is safe to move and transport for destruction.

There’s a fundamental principle here that can be applied to many hazardous substances, and that is competence in handling: ensuring that anyone handling hazardous substances is firstly aware of the latent hazards and has been suitably briefed on safety precautions, is aware of the basic (hazardous substance) symbology, classifications and incompatibilities, and knows who is available in their workplace to provide further advice or supervision, ie a certified Approved Handler or other competent person.

MIKE NANKIVELL is a senior hazardous substances consultant and Test Certifier with HazTec.

Suzanne Broadbent is a scientist and occupational hygienist with Auckland-based consultancy HaS-Expertise.

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