|
|
|
|
|
17 October 2025
|
Featured FRI Magazine article: Hazardous materials – explosives by Colin Deiner
Rescue personnel search the damage to an apartment complex from the explosion of the West Fertiliser plant, Texas
|
26 die as fireworks truck explodes in China
|
First responders at the Boston Marathon explosions
|
A Colorado wastewater facility storing organic peroxide went up in flames after a fracking tanker was hit by lightning
|
This week’s featured Fire and Rescue International magazine article is: Hazardous materials – explosives, written by Colin Deiner, Chief Director, Disaster Management and Fire Brigade Services, Western Cape Government (FRI Vol 3 no 8). We will be sharing more technical/research/tactical articles from Fire and Rescue International magazine on a weekly basis with our readers to assist in technology transfer. This will hopefully create an increased awareness, providing you with hands-on advice and guidance. All our magazines are available free of charge in PDF format on our website and online at ISSUU. We also provide all technical articles as a free download in our article archive on our website.
Hazardous materials – explosives
By Colin Deiner, Chief Director, Disaster Management and Fire Brigade Services, Western Cape Government
The use of chemicals to enhance and improve life has become a globally accepted practice, it virtually goes without saying. Unfortunately, with the advantages comes the risk that many of these chemicals come. Most countries have developed standards for handling and transporting these chemicals and there are many protocols for responding to emergencies involving the wide range of hazardous chemicals in use all over the world. The toxic spill handled by a hazardous material (hazmat) unit from the New York Fire Department in Lower Manhattan will be no different from the toxic spill in downtown Lagos, Nigeria. The worldwide (sometimes uncontrolled) movement of hazardous materials many times results in a hazardous material with a specific risk profile ending up in a country with very different laws than the country it was manufactured and packaged in. We need to be able to identify these products, understand their risks and respond effectively to emergencies where they may be involved.
This is the first article in series of nine dealing with the United Nations Committee of Experts on the Transportation of Dangerous Goods (UNCOE). Classes of hazardous materials. In each of these I will attempt to delineate the risk and provide some thoughts on managing the incident. To keep you interested and allow me to address other fire/rescue subjects we won’t do all of them in sequence but try to throw one in every two or three issues.
As we know all hazardous materials are classified according to their particular properties. These classes are:
We will start with explosives.
Explosives
Of all the hazmat incidents you can respond to, incidents involving explosives will have the biggest and most immediate risk. Explosives are generally highly regulated and it is therefore unlikely that fire services will respond to major fires in explosive installations. The one type of explosive you will probably deal with more regularly is fireworks. Yes folks, fireworks are explosives. Consider the large amounts of fireworks sold legally and illegally in South Africa every year, especially during the festive seasons; where do the vendors store them? When they are confiscated by law enforcement agencies, do they have sufficient disposal facilities or are they stored in bulk somewhere? This is a problem and must be addressed by all emergency services.
Explosives will either burn very intensely (deflagrate) or explode (detonate). A detonation will cause a rapid energy release accompanied by a shock wave with enough force to displace objects of various sizes very quickly and result in devastation; often on a huge scale. Deflagration is caused when the ignited material burns with extreme ferocity and spreads through this material at a rapid rate.
Commercial explosives are normally activated by way of a detonator, which is as a rule stored and transported separately. They can also be initiated by means of friction, impact, heat (fire), overpressure, fragmentation, electrostatic discharges or, in the event of electro-explosive devices, electromagnetic radiation.
Classification of explosives
The United Nations Committee of Experts (UNCOE) on the transport of dangerous goods classifies dangerous goods on the hazards they present in the form in which they are transported. Explosives are classified as follows:
The UN classification scheme further classifies explosives according to their hazard potential. Hazard Type 1 includes all those explosives that have a mass explosion hazard. A mass explosion hazard means that in the event of an explosion the entire load will be affected instantaneously. Expect major structural collapse if this was to occur in a confined space. Type 2 Hazard explosives will cause a projection hazard eg mortars but no mass explosion hazard while Type 3 explosives will cause a fire (deflagration) or blast hazard, which will cause considerable radiant heat further causing a projection or blast hazard. Type 4 Hazard explosives will only cause a minor explosion during transport or storage and will only cause a localised effect, normally confined to its packaging. The contents of the entire load will also not generally be affected. Small arms ammunition falls into this category.
The final classification is Type 5 class explosives, which describe extremely insensitive substances that have a mass explosion hazard but have very little probability of an initiation or of a transition from burning to detonation under normal transport conditions. Ammonium nitrate fuel oil (a preparation for blasting) falls into this classification.
Explosive hazards
A blast has two phases; the first is the positive phase that forms from the compression of air in front of the blast wave, which heats and accelerates the movement of air molecules (over pressurisation). The negative-phase follows this and is as a result of the ‘under pressurisation’ caused by the vacuum effect of the preceding over-pressurisation.
People exposed to explosive events will generally suffer some sort of ‘blast injury’. Blast injuries are characterised by severe anatomical and physiological impacts from the direct or reflected over-pressurisation force impacting on the body’s surface. The severity of this impact is dependent on the distance of the individual to the explosion, its peak pressure, duration and location (indoors, outdoors or in water).
The primary blast injuries will be those suffered due to direct exposure to the blast. The most severe of these would be lung haemorrhaging (pulmonary barotrauma), which would be the most likely cause of death in fatal primary blast injuries. Other injuries could include middle ear damage, abdominal haemorrhaging and perforation, eye rupture and concussion (transient brain injury). A fireball created by an explosion with high temperature will cause severe burns to victims close to the point of explosion.
Secondary blast injuries can occur some distance from the explosion and results from flying debris and explosives fragments. Penetrating injuries from flying sharp objects (glass) or blunt injuries caused by falling masonry are the most common here. Asphyxiation caused by the propagation of large columns of dust is another cause of secondary blast injuries. This was a major risk presented to the people in the vicinity of the World Trade Centre Twin Towers during the 911 attacks in 2001.
Tertiary blast injuries are those that occur due to a person being thrown over by the blast effect. This can result in fractures and/or traumatic amputation and brain injuries. A fourth blast impact injury can develop later in the victim’s life and includes the kinds of illnesses that can be directly linked to the explosion such as asthma, chronic obstructive pulmonary disease (COPD), hyperglycaemia and hypertension are included here.
In addition to these classifications, explosions can also cause severe burns due to conflagration (no explosion), to hearing impairment due to the noise propagation of the blast and of course structural collapse, which is generally the largest cause of explosive related death.
Common types of explosives
Explosives are used in a wide range of applications and it is therefore important that we understand these applications in our response areas. How it is stored and transported. To understand all explosives and their applications is virtually impossible. We are fire fighters, not chemists or explosives experts. We need to develop a common-sense approach to hazardous materials. This means that we should have a system where we are able to understand how to identify hazardous materials classes, their risks and how to safely manage them. Having a good understanding of the most common explosives is essential.
So, which are those that we need to know more about:
Nitro-glycerine: This is an extremely sensitive liquid explosive, which is mixed with other inert products to manufacture propellants, dynamite and blasting gelatines. Nitroglycerine is sensitive to flame, heat, shock, oxygen and ultra-violet radiation and due to its instability is not handled or transported in its pure form. It is generally transported in a diluted solution with alcohol or in a mixture with a solid dilutant for pharmaceutical purposes. When dynamite comes into contact with water it may tend to release nitro-glycerine. This is important in firefighting operations. Nitro-glycerine is also an extremely toxic substance and can be absorbed through the skin. Consider the decontamination challenges such an incident may present.
Trinitrotoluene (TNT): is a comparatively stable explosive mostly used in military applications. This solid substance is relatively safe to handle and can burn out in small quantities. Larger quantities can, however, burn to detonation, specifically in confined areas. TNT gives of toxic fumes when it burns and is also toxic when ingested. It is also able to be absorbed through the skin.
Nitrocellulose: is a white, fibrous material produced in a variety of forms and its properties are determined by the amount of nitrogen content. Those with a nitrogen content of higher than 12.7 (explosives grade) are generally used for explosives. Nitrocellulose is extremely sensitive to impact and friction in its dry state and ignites easily when exposed to flame. It is generally transported in a wet state ie in water and alcohol, or plasticised. Non-explosive grade nitrocellulose will normally burn and is classified as a class 4.1 flammable solid (we will deal with this more in the article covering flammable solids in the near future). The main uses for nitrocellulose are as an ingredient in propellant mixtures for ammunition and rocket motors and in nitro-glycerine explosives. Non-explosive grades of cellulose-nitrate are used in the manufacture paints and lacquers.
Primary explosives (fulminates, azides and stephnates): These are known as ‘initiating explosives’ and are commonly used in detonators and blasting cap compositions. They are highly dangerous and sensitive and explode violently particularly when they contain heavy metals such as mercury, lead and silver. In bulk mode they are also packaged and transported in water or a wetting agent, which provides more stability. Their containers are also designed to prevent leakage. In processed form they will typically be in compressed pellet form or cast into aluminium tubes. In this form they will be highly sensitive to impact and electrical discharge. Packaging is designed to withstand impact but to a limited extent only, such as 1,5 metre drops. Severe impact may cause the package to break open, spilling the contents and thereby increasing the risk factor. Accidentally stepping with a heavy boot on such a small aluminium tube could cause a detonation with sufficient force to lose the foot and lower leg, so care should be taken when approaching such a scene.
Gun powder/black powder/black blasting powder: are generally made from a mixture of charcoal, sulphur and potassium nitrate. They are extremely sensitive to ignition from sparks, heat and friction and burn violently in open spaces propagating huge volumes of acrid smoke. They could, however, cause an explosion if ignited in a confined space. Black powder is used as a blasting explosive as well as an ingredient in certain types of gun-sports cartridges, fireworks and pyro techniques.
Oxidisers: are not generally classed as explosives and actually have their own UN classification (5. Oxidising agents and organic peroxides). They can, however, under certain fire conditions explode and for this reason I am including two types, nitrates and chlorates here. Nitrates are used in explosives such as gunpowder, emulsion and slurry blasting explosives and in pyrotechnic devices. The most common are potassium, sodium, barium and ammonium nitrates, all of which when mixed with fuel, can burn violently and even explode.
Ammonium nitrate is widely used in the agricultural industry as a fertiliser and forms the base for ammonium nitrate and fuel oil explosives. Due to the availability of the ingredients and ease of transport and manufacture this has become a weapon favoured by various terrorist organisations in recent years. The bombing of the Murrah Building in Oklahoma City in 1995, which claimed the lives of 168 people, was an example of commercially available ammonium nitrate being used to develop a terrorist weapon.
Chlorates, particularly potassium chlorate, are used in pyrotechnic applications and, as with nitrates, can decompose violently in a fire. Chlorates are generally less stable than nitrates.
Emulsion and slurry explosives: are relatively new types of explosives, which are mixtures of nitrates and other products in a water-based system. They are replacing nitro-glycerine based explosives for a range of applications, particularly in quarrying. The various products are transported to the blasting site separately and then mixed on-site prior to the blasting activity in a specially designed mix-truck making it a more stable process.
Peroxide explosives: are improvised or ‘home-made’ explosives and are constituted from various commercial products, which can be found in any supermarket. These can be: hydrogen peroxide (hair dye), acid (battery acid, citric acid), acetone (nail varnish remover) and hexamine (fuel stove tablets). These explosive are cheap to manufacture, have readily available elements and are hard to identify. A close friend of mine in the South African Police Service (SAPS) was regularly involved in raiding clandestine drug laboratories (many in upmarket residential areas). In the course of his work, he often had to identify and assist in the defusing of these types of booby traps set up inside the clandestine lab. A responding fire service should not except that any fire in a high class neighbourhood is always just a routine fire. Be careful for these kinds of situations. Unfortunately, pre-incident inspections do not generally happen in these establishments.
Managing the incident (pre-planning)
Due to their unique and high hazard properties, planning for incidents involving explosives is critical. Fortunately, the explosives industry is highly regulated and it should therefore not be too difficult to identify storage and manufacturing facilities. The strict regulations relating to the design of these facilities should provide further assistance to the responding agencies in the event of an incident. These provisions include ie the prevention of confined spaces, safety of electrical appliances, lightning protectors, provision of escape routes and the vertical clearance requirements between buildings and overhead power lines.
Pre-planning should include the location of the explosives, their quantities and hazard classifications and the licence provisions for the site. The construction type of the storage and manufacturing buildings must also be evaluated and any features that may affect firefighting operations must be taken into account. The potential for fire spread and potential movement of toxic gasses and elements of combustion are important. Although it shouldn’t form part of the design (by regulation) also check for unprotected shafts and openings. Finally, take a lot of time to access the structural collapse risk of the premises.
For firefighting and search and rescue operations the layout of the site is important. This will determine where to place your specialised vehicles such as your aerial apparatus and also safe defensive firefighting positons. You will also ascertain the type and position of fixed firefighting systems. Does the site have additional water supplies; what are the distances from them and what are the pressure implications? A series of ground plans also needs to be developed indicating the initial staging point, secondary staging positions and locations of command posts, breathing apparatus points and decontamination areas. It should also include escape routes and safety zones. When safety zones are identified, take into account the possibility of projectiles and that it would provide sufficient distance from large, intense fires. Here you will, by default, go defensive.
The manufacture of explosives is a complicated activity and a number of auxiliary processes will be running simultaneously, each one posing their own particular hazard. Look out for overhead or underground oil and gas pipelines supplying products for storage or the manufacturing process. Electrical transformers and sub-stations, compressed gasses and drainage catchment systems might also be in close proximity. Also, try to identify the various environmental protection systems that may impact operations.
Of course, the usual information such as the details of site supervisors and safety officers, expert advisors etc should form part of your plan.
Fire safety inspections by your department’s fire prevention division should include consultation with representatives of the inspector of explosives, as determined by legislation. This will provide your staff with the necessary knowledge that might otherwise not be readily available in fire services.
As always, exercise regularly. Make sure all role-players participate in these exercises and alternate them to make sure that all possible scenarios are covered over a period of time.
Military applications
If you have a military explosives installation in your area of jurisdiction work together with them to determine exactly what they require of you. Compliance with the Major Hazard Installations Act will require your staff to undergo certain compliance procedures and the security of the information you need to conduct your pre-planning must be adhered to. There will generally be very good emergency procedures in place and it is our role to know where we fit into the picture.
CBRNE
Chemical, biological, radiological, nuclear, and explosive (CBRNE) response is a concept that developed post 911 and refers to terrorist incidents whereby any of the previously mentioned products are used as weapons to cause harm to people and destruction to infrastructure and the environment. The scope of this article is not wide enough to cover the entire concept of CBRNE; however, I think it is important to mention here that in the event of such an incident, the rules of the game may change considerably. A favoured tactic of terrorists is to trigger a single incident and then wait for emergency services to arrive on scene and start working before triggering a second event. While South Africa is not subjected to major acts of terror, recent events worldwide cannot rule out the possibility of it occurring in future. It would be highly negligent of any service to rule this out completely.
Explosions caused by acts of terror can vary significantly. You will find that most recent major terror attacks have been conventional attacks using aircraft, explosives and standard firearms rather than intricate spy novel type devices. In order to activate a sensitive device, it needs to be clandestinely transported to the site and will also require a large amount of product ie explosives, gas, liquid etc to cause the intended harm. Consider the logistics, then realise why we don’t see these incidents happen.
Managing the incident (response)
The incident response begins with the information gathered by the call-taker. Make sure that a specific procedure is in place for the call-taker to utilise when a call is received involving hazardous materials and in this case, explosives. Standard operating procedures (SOPs) are as important in the despatch centre as on the fire ground. This information, together with your pre-plan, will then form the basis for your response.
The incident must be approached with caution while the crew looks out for visual indicators that could determine the nature/severity of the incident. Upon arrival check if the pre-determined staging area is still viable (it might have been compromised by the blast) and announce arrival and position to all other units. Then try to contact the site safety and management representatives. They will be able to provide you with the latest information related to the emergency, what product is involved, how much of it is involved, how many people are missing, injured or trapped and what mitigation systems have been activated.
After establishing command it, will be necessary to identify and clearly indicate the inner cordon (hot zone). It must be strictly controlled and ingress into it must be by command decision only. The primary staging area for those units that will be immediately needed to deal with the incident must be established and its position communicated to arriving units. The secondary staging area must be established for all other arriving units who will not be committed to the incident immediately and may be used later on in the incident. This is especially important if you are responding to a multi-jurisdictional, mutual-aid alarm where not a lot of combined drills and exercises have taken place. Incoming units must be firmly dealt with when they are diverted to the secondary staging area and a staging officer must be placed there to control all vehicle and troop movements.
The minimum safety zones will differ depending on the type of product you are dealing with. Ensure that you have a clear guideline for all units indicating the best recommended safety distances for the classes and types of explosives you might have to deal with.
Once your command position is set up and the incident can be approached from a safe distance decisions will have to be made regarding the following:
Advancing into the hot zone
If it is considered safe for crews to advance into the hot zone to start conducting firefighting or search-and-rescue work, make it clear that a number of unstable, unexploded materials could still be lying all over. They should not touch or step on anything they are not familiar with. In a suspected clandestine drug lab try, to avoid any jars containing gels or powders and move very carefully avoiding any taught wires or similar possible booby traps.
Ultimately, if there is very little or no chance of saving lives, rather take a defensive stance. Buildings can be replaced, lives can’t.
Incident command
The magnitude of the incident will determine the size and complexity of the command system. It might also determine if the command post stays where it was initially established or if it is moved to amore tactically convenient position. The valuable information collected by the first arriving units will be vital in deciding the objectives and plan of action for the foreseeable durations of the incident.
Your initial object will be the saving and protection of lives. This will require an evacuation of everybody inside the hot zone. To do this you might have to commit some of your forces to assist injured and disoriented people. Only do this if you are satisfied that the situation is stable enough to commit them. The next part of saving lives will be search and rescue. Make sure that your search-and-rescue teams are well trained in this and are monitored throughout the operation. Also identify safe areas close to their general positions where they can run to when things start going south. They should also have a back-up team on standby to rush to their aid if they are injured or to assist in removing any victims they might have recovered.
Your second objective would be to prevent the fire from reaching any explosives. If you are able to attempt this ensure that your water streams are placed between the fire and the explosives and attempt to work the fire away from the risk. Also ensure that any exposures that could conduct heat to the explosive storage areas are adequately cooled down. You might want to consider placing unmanned monitors in position to protect exposures and limit fire spread if it is an extremely high risk environment.
All this time, however, you must ensure that all crews committed to the operation must have an escape route. Continuously evaluate the movement of your crews and adapt the escape routes accordingly.
If the fire has reached the explosives, an immediate withdrawal must be implemented. The application of water will not extinguish them. All fire crews must be familiar with the pre-determined withdrawal alarm and this must be activated well in advance of any possible flame impingement on the explosives containers. It is here where the ‘RLH’ component of our tactical withdrawal has priority (RLH = Run like Hell).
If an explosion were to happen following your withdrawal, take care not to commit resources immediately thereafter. Structures could have become unstable and the possibility of secondary explosions cannot be ruled out. Only after consultation with the site representatives, explosives experts and other essential command staff can fire fighting be resumed.
Advice for operational crews
Crews involved in fire fighting and support activities must realise the unique dynamics of the incident they are dealing with. The most important of these will be to ensure that they are in constant communication with their sector and that this is maintained throughout the incident. Be careful, however, when working with radios inside the hot zone. No radio-frequency transmission is to be allowed within a ten-metre radius from an electro-explosive device. Vehicle mounted radios with an effective radiated output exceeding five Watt should not be allowed to transmit within 50 metres of the hot zone.
People must never work alone in the hot zone and should only enter the hot zone to do essential work. When identifying safe zones, bear in mind that single layer brick structures may afford little protection. Large explosives storage and manufacturing facilities usually have well established safety structures which will form part of your pre-planning map.
Incident termination
The incident command team will have to keep a tight rein on all activities and respond to any changes in the situation, finally bringing the incident to a successful conclusion.
Before terminating the incident and announcing an ‘all clear’, command should be satisfied that any residual hazards that may have developed during the operation have been dealt with and have been made safe. If the explosion caused a structural collapse and trapped people have to be rescued, it will be necessary to call in the department rescue squad or even the regional urban search and rescue team. Explosives experts and fire crews will then have to remain on scene while the collapsed structure is being delayered to ensure that no explosives products have remained that are able to cause an additional risk.
Notwithstanding the above, the incident commander should liaise with the department fire safety officer and any explosives inspectors and inform them of all his/her observations during the acute operational phase. These observations could be vital in determining the cause of the fire/explosion and provide helpful information on preventing further similar events.
South African law will require your service to hand the scene over to the police services and inspector of explosives following the incident termination.
In closing
I hope you have found this first article on the nine classes of hazardous materials valuable and interesting. I recall a large wildfire some years back where a 50-kilometre per hour wind was pushing the flames right up against a munitions warehouse. The fire service, assisted by helicopters, was able to prevent a major catastrophe by getting enough water between the fire and the building. This was only due to a strong incident commander and a well-established command system. The rapid decision making required for incidents involving explosives will require this.
Hazardous materials – explosives
By Colin Deiner, Chief Director, Disaster Management and Fire Brigade Services, Western Cape Government
The use of chemicals to enhance and improve life has become a globally accepted practice, it virtually goes without saying. Unfortunately, with the advantages comes the risk that many of these chemicals come. Most countries have developed standards for handling and transporting these chemicals and there are many protocols for responding to emergencies involving the wide range of hazardous chemicals in use all over the world. The toxic spill handled by a hazardous material (hazmat) unit from the New York Fire Department in Lower Manhattan will be no different from the toxic spill in downtown Lagos, Nigeria. The worldwide (sometimes uncontrolled) movement of hazardous materials many times results in a hazardous material with a specific risk profile ending up in a country with very different laws than the country it was manufactured and packaged in. We need to be able to identify these products, understand their risks and respond effectively to emergencies where they may be involved.
This is the first article in series of nine dealing with the United Nations Committee of Experts on the Transportation of Dangerous Goods (UNCOE). Classes of hazardous materials. In each of these I will attempt to delineate the risk and provide some thoughts on managing the incident. To keep you interested and allow me to address other fire/rescue subjects we won’t do all of them in sequence but try to throw one in every two or three issues.
As we know all hazardous materials are classified according to their particular properties. These classes are:
- Explosives
- Gasses
- Flammable liquids
- Flammable Solids
- Oxidising agents and organic peroxides
- Toxic and infectious substances
- Radioactive materials
- Corrosive substances
- Miscellaneous substances.
We will start with explosives.
Explosives
Of all the hazmat incidents you can respond to, incidents involving explosives will have the biggest and most immediate risk. Explosives are generally highly regulated and it is therefore unlikely that fire services will respond to major fires in explosive installations. The one type of explosive you will probably deal with more regularly is fireworks. Yes folks, fireworks are explosives. Consider the large amounts of fireworks sold legally and illegally in South Africa every year, especially during the festive seasons; where do the vendors store them? When they are confiscated by law enforcement agencies, do they have sufficient disposal facilities or are they stored in bulk somewhere? This is a problem and must be addressed by all emergency services.
Explosives will either burn very intensely (deflagrate) or explode (detonate). A detonation will cause a rapid energy release accompanied by a shock wave with enough force to displace objects of various sizes very quickly and result in devastation; often on a huge scale. Deflagration is caused when the ignited material burns with extreme ferocity and spreads through this material at a rapid rate.
Commercial explosives are normally activated by way of a detonator, which is as a rule stored and transported separately. They can also be initiated by means of friction, impact, heat (fire), overpressure, fragmentation, electrostatic discharges or, in the event of electro-explosive devices, electromagnetic radiation.
Classification of explosives
The United Nations Committee of Experts (UNCOE) on the transport of dangerous goods classifies dangerous goods on the hazards they present in the form in which they are transported. Explosives are classified as follows:
- Explosive substances: A solid or liquid substance (or combination), which is in itself capable by chemical reaction of producing gas at such temperature and pressure and at such speed as could cause damage to surroundings. Of these, dynamite is probably the best example.
- Pyrotechnic substances: A substance (or mixture of substances) designed to produce an effect by heat, light, sound, gas, smoke or a combination of these as a result of non-detonating, self-sustaining exothermic chemical reactions. This is where fireworks are placed.
- Explosive articles: Ammunition capable of producing explosions is classified according to this category.
The UN classification scheme further classifies explosives according to their hazard potential. Hazard Type 1 includes all those explosives that have a mass explosion hazard. A mass explosion hazard means that in the event of an explosion the entire load will be affected instantaneously. Expect major structural collapse if this was to occur in a confined space. Type 2 Hazard explosives will cause a projection hazard eg mortars but no mass explosion hazard while Type 3 explosives will cause a fire (deflagration) or blast hazard, which will cause considerable radiant heat further causing a projection or blast hazard. Type 4 Hazard explosives will only cause a minor explosion during transport or storage and will only cause a localised effect, normally confined to its packaging. The contents of the entire load will also not generally be affected. Small arms ammunition falls into this category.
The final classification is Type 5 class explosives, which describe extremely insensitive substances that have a mass explosion hazard but have very little probability of an initiation or of a transition from burning to detonation under normal transport conditions. Ammonium nitrate fuel oil (a preparation for blasting) falls into this classification.
Explosive hazards
A blast has two phases; the first is the positive phase that forms from the compression of air in front of the blast wave, which heats and accelerates the movement of air molecules (over pressurisation). The negative-phase follows this and is as a result of the ‘under pressurisation’ caused by the vacuum effect of the preceding over-pressurisation.
People exposed to explosive events will generally suffer some sort of ‘blast injury’. Blast injuries are characterised by severe anatomical and physiological impacts from the direct or reflected over-pressurisation force impacting on the body’s surface. The severity of this impact is dependent on the distance of the individual to the explosion, its peak pressure, duration and location (indoors, outdoors or in water).
The primary blast injuries will be those suffered due to direct exposure to the blast. The most severe of these would be lung haemorrhaging (pulmonary barotrauma), which would be the most likely cause of death in fatal primary blast injuries. Other injuries could include middle ear damage, abdominal haemorrhaging and perforation, eye rupture and concussion (transient brain injury). A fireball created by an explosion with high temperature will cause severe burns to victims close to the point of explosion.
Secondary blast injuries can occur some distance from the explosion and results from flying debris and explosives fragments. Penetrating injuries from flying sharp objects (glass) or blunt injuries caused by falling masonry are the most common here. Asphyxiation caused by the propagation of large columns of dust is another cause of secondary blast injuries. This was a major risk presented to the people in the vicinity of the World Trade Centre Twin Towers during the 911 attacks in 2001.
Tertiary blast injuries are those that occur due to a person being thrown over by the blast effect. This can result in fractures and/or traumatic amputation and brain injuries. A fourth blast impact injury can develop later in the victim’s life and includes the kinds of illnesses that can be directly linked to the explosion such as asthma, chronic obstructive pulmonary disease (COPD), hyperglycaemia and hypertension are included here.
In addition to these classifications, explosions can also cause severe burns due to conflagration (no explosion), to hearing impairment due to the noise propagation of the blast and of course structural collapse, which is generally the largest cause of explosive related death.
Common types of explosives
Explosives are used in a wide range of applications and it is therefore important that we understand these applications in our response areas. How it is stored and transported. To understand all explosives and their applications is virtually impossible. We are fire fighters, not chemists or explosives experts. We need to develop a common-sense approach to hazardous materials. This means that we should have a system where we are able to understand how to identify hazardous materials classes, their risks and how to safely manage them. Having a good understanding of the most common explosives is essential.
So, which are those that we need to know more about:
Nitro-glycerine: This is an extremely sensitive liquid explosive, which is mixed with other inert products to manufacture propellants, dynamite and blasting gelatines. Nitroglycerine is sensitive to flame, heat, shock, oxygen and ultra-violet radiation and due to its instability is not handled or transported in its pure form. It is generally transported in a diluted solution with alcohol or in a mixture with a solid dilutant for pharmaceutical purposes. When dynamite comes into contact with water it may tend to release nitro-glycerine. This is important in firefighting operations. Nitro-glycerine is also an extremely toxic substance and can be absorbed through the skin. Consider the decontamination challenges such an incident may present.
Trinitrotoluene (TNT): is a comparatively stable explosive mostly used in military applications. This solid substance is relatively safe to handle and can burn out in small quantities. Larger quantities can, however, burn to detonation, specifically in confined areas. TNT gives of toxic fumes when it burns and is also toxic when ingested. It is also able to be absorbed through the skin.
Nitrocellulose: is a white, fibrous material produced in a variety of forms and its properties are determined by the amount of nitrogen content. Those with a nitrogen content of higher than 12.7 (explosives grade) are generally used for explosives. Nitrocellulose is extremely sensitive to impact and friction in its dry state and ignites easily when exposed to flame. It is generally transported in a wet state ie in water and alcohol, or plasticised. Non-explosive grade nitrocellulose will normally burn and is classified as a class 4.1 flammable solid (we will deal with this more in the article covering flammable solids in the near future). The main uses for nitrocellulose are as an ingredient in propellant mixtures for ammunition and rocket motors and in nitro-glycerine explosives. Non-explosive grades of cellulose-nitrate are used in the manufacture paints and lacquers.
Primary explosives (fulminates, azides and stephnates): These are known as ‘initiating explosives’ and are commonly used in detonators and blasting cap compositions. They are highly dangerous and sensitive and explode violently particularly when they contain heavy metals such as mercury, lead and silver. In bulk mode they are also packaged and transported in water or a wetting agent, which provides more stability. Their containers are also designed to prevent leakage. In processed form they will typically be in compressed pellet form or cast into aluminium tubes. In this form they will be highly sensitive to impact and electrical discharge. Packaging is designed to withstand impact but to a limited extent only, such as 1,5 metre drops. Severe impact may cause the package to break open, spilling the contents and thereby increasing the risk factor. Accidentally stepping with a heavy boot on such a small aluminium tube could cause a detonation with sufficient force to lose the foot and lower leg, so care should be taken when approaching such a scene.
Gun powder/black powder/black blasting powder: are generally made from a mixture of charcoal, sulphur and potassium nitrate. They are extremely sensitive to ignition from sparks, heat and friction and burn violently in open spaces propagating huge volumes of acrid smoke. They could, however, cause an explosion if ignited in a confined space. Black powder is used as a blasting explosive as well as an ingredient in certain types of gun-sports cartridges, fireworks and pyro techniques.
Oxidisers: are not generally classed as explosives and actually have their own UN classification (5. Oxidising agents and organic peroxides). They can, however, under certain fire conditions explode and for this reason I am including two types, nitrates and chlorates here. Nitrates are used in explosives such as gunpowder, emulsion and slurry blasting explosives and in pyrotechnic devices. The most common are potassium, sodium, barium and ammonium nitrates, all of which when mixed with fuel, can burn violently and even explode.
Ammonium nitrate is widely used in the agricultural industry as a fertiliser and forms the base for ammonium nitrate and fuel oil explosives. Due to the availability of the ingredients and ease of transport and manufacture this has become a weapon favoured by various terrorist organisations in recent years. The bombing of the Murrah Building in Oklahoma City in 1995, which claimed the lives of 168 people, was an example of commercially available ammonium nitrate being used to develop a terrorist weapon.
Chlorates, particularly potassium chlorate, are used in pyrotechnic applications and, as with nitrates, can decompose violently in a fire. Chlorates are generally less stable than nitrates.
Emulsion and slurry explosives: are relatively new types of explosives, which are mixtures of nitrates and other products in a water-based system. They are replacing nitro-glycerine based explosives for a range of applications, particularly in quarrying. The various products are transported to the blasting site separately and then mixed on-site prior to the blasting activity in a specially designed mix-truck making it a more stable process.
Peroxide explosives: are improvised or ‘home-made’ explosives and are constituted from various commercial products, which can be found in any supermarket. These can be: hydrogen peroxide (hair dye), acid (battery acid, citric acid), acetone (nail varnish remover) and hexamine (fuel stove tablets). These explosive are cheap to manufacture, have readily available elements and are hard to identify. A close friend of mine in the South African Police Service (SAPS) was regularly involved in raiding clandestine drug laboratories (many in upmarket residential areas). In the course of his work, he often had to identify and assist in the defusing of these types of booby traps set up inside the clandestine lab. A responding fire service should not except that any fire in a high class neighbourhood is always just a routine fire. Be careful for these kinds of situations. Unfortunately, pre-incident inspections do not generally happen in these establishments.
Managing the incident (pre-planning)
Due to their unique and high hazard properties, planning for incidents involving explosives is critical. Fortunately, the explosives industry is highly regulated and it should therefore not be too difficult to identify storage and manufacturing facilities. The strict regulations relating to the design of these facilities should provide further assistance to the responding agencies in the event of an incident. These provisions include ie the prevention of confined spaces, safety of electrical appliances, lightning protectors, provision of escape routes and the vertical clearance requirements between buildings and overhead power lines.
Pre-planning should include the location of the explosives, their quantities and hazard classifications and the licence provisions for the site. The construction type of the storage and manufacturing buildings must also be evaluated and any features that may affect firefighting operations must be taken into account. The potential for fire spread and potential movement of toxic gasses and elements of combustion are important. Although it shouldn’t form part of the design (by regulation) also check for unprotected shafts and openings. Finally, take a lot of time to access the structural collapse risk of the premises.
For firefighting and search and rescue operations the layout of the site is important. This will determine where to place your specialised vehicles such as your aerial apparatus and also safe defensive firefighting positons. You will also ascertain the type and position of fixed firefighting systems. Does the site have additional water supplies; what are the distances from them and what are the pressure implications? A series of ground plans also needs to be developed indicating the initial staging point, secondary staging positions and locations of command posts, breathing apparatus points and decontamination areas. It should also include escape routes and safety zones. When safety zones are identified, take into account the possibility of projectiles and that it would provide sufficient distance from large, intense fires. Here you will, by default, go defensive.
The manufacture of explosives is a complicated activity and a number of auxiliary processes will be running simultaneously, each one posing their own particular hazard. Look out for overhead or underground oil and gas pipelines supplying products for storage or the manufacturing process. Electrical transformers and sub-stations, compressed gasses and drainage catchment systems might also be in close proximity. Also, try to identify the various environmental protection systems that may impact operations.
Of course, the usual information such as the details of site supervisors and safety officers, expert advisors etc should form part of your plan.
Fire safety inspections by your department’s fire prevention division should include consultation with representatives of the inspector of explosives, as determined by legislation. This will provide your staff with the necessary knowledge that might otherwise not be readily available in fire services.
As always, exercise regularly. Make sure all role-players participate in these exercises and alternate them to make sure that all possible scenarios are covered over a period of time.
Military applications
If you have a military explosives installation in your area of jurisdiction work together with them to determine exactly what they require of you. Compliance with the Major Hazard Installations Act will require your staff to undergo certain compliance procedures and the security of the information you need to conduct your pre-planning must be adhered to. There will generally be very good emergency procedures in place and it is our role to know where we fit into the picture.
CBRNE
Chemical, biological, radiological, nuclear, and explosive (CBRNE) response is a concept that developed post 911 and refers to terrorist incidents whereby any of the previously mentioned products are used as weapons to cause harm to people and destruction to infrastructure and the environment. The scope of this article is not wide enough to cover the entire concept of CBRNE; however, I think it is important to mention here that in the event of such an incident, the rules of the game may change considerably. A favoured tactic of terrorists is to trigger a single incident and then wait for emergency services to arrive on scene and start working before triggering a second event. While South Africa is not subjected to major acts of terror, recent events worldwide cannot rule out the possibility of it occurring in future. It would be highly negligent of any service to rule this out completely.
Explosions caused by acts of terror can vary significantly. You will find that most recent major terror attacks have been conventional attacks using aircraft, explosives and standard firearms rather than intricate spy novel type devices. In order to activate a sensitive device, it needs to be clandestinely transported to the site and will also require a large amount of product ie explosives, gas, liquid etc to cause the intended harm. Consider the logistics, then realise why we don’t see these incidents happen.
Managing the incident (response)
The incident response begins with the information gathered by the call-taker. Make sure that a specific procedure is in place for the call-taker to utilise when a call is received involving hazardous materials and in this case, explosives. Standard operating procedures (SOPs) are as important in the despatch centre as on the fire ground. This information, together with your pre-plan, will then form the basis for your response.
The incident must be approached with caution while the crew looks out for visual indicators that could determine the nature/severity of the incident. Upon arrival check if the pre-determined staging area is still viable (it might have been compromised by the blast) and announce arrival and position to all other units. Then try to contact the site safety and management representatives. They will be able to provide you with the latest information related to the emergency, what product is involved, how much of it is involved, how many people are missing, injured or trapped and what mitigation systems have been activated.
After establishing command it, will be necessary to identify and clearly indicate the inner cordon (hot zone). It must be strictly controlled and ingress into it must be by command decision only. The primary staging area for those units that will be immediately needed to deal with the incident must be established and its position communicated to arriving units. The secondary staging area must be established for all other arriving units who will not be committed to the incident immediately and may be used later on in the incident. This is especially important if you are responding to a multi-jurisdictional, mutual-aid alarm where not a lot of combined drills and exercises have taken place. Incoming units must be firmly dealt with when they are diverted to the secondary staging area and a staging officer must be placed there to control all vehicle and troop movements.
The minimum safety zones will differ depending on the type of product you are dealing with. Ensure that you have a clear guideline for all units indicating the best recommended safety distances for the classes and types of explosives you might have to deal with.
Once your command position is set up and the incident can be approached from a safe distance decisions will have to be made regarding the following:
- The possibility of a secondary explosive device being detonated. You might have to allow the police bomb disposal squads to enter the hot zone and do a sweep for any additional bombs (in the event of a terrorist attack)
- The necessity for activating your city’s major incident or disaster contingency plan
- The need for any search and rescue
- Determine the operational mode (offensive or defensive)
- Additional resource requirements
- Neutralisation and isolation of any auxiliary systems and additional hazards
Advancing into the hot zone
If it is considered safe for crews to advance into the hot zone to start conducting firefighting or search-and-rescue work, make it clear that a number of unstable, unexploded materials could still be lying all over. They should not touch or step on anything they are not familiar with. In a suspected clandestine drug lab try, to avoid any jars containing gels or powders and move very carefully avoiding any taught wires or similar possible booby traps.
Ultimately, if there is very little or no chance of saving lives, rather take a defensive stance. Buildings can be replaced, lives can’t.
Incident command
The magnitude of the incident will determine the size and complexity of the command system. It might also determine if the command post stays where it was initially established or if it is moved to amore tactically convenient position. The valuable information collected by the first arriving units will be vital in deciding the objectives and plan of action for the foreseeable durations of the incident.
Your initial object will be the saving and protection of lives. This will require an evacuation of everybody inside the hot zone. To do this you might have to commit some of your forces to assist injured and disoriented people. Only do this if you are satisfied that the situation is stable enough to commit them. The next part of saving lives will be search and rescue. Make sure that your search-and-rescue teams are well trained in this and are monitored throughout the operation. Also identify safe areas close to their general positions where they can run to when things start going south. They should also have a back-up team on standby to rush to their aid if they are injured or to assist in removing any victims they might have recovered.
Your second objective would be to prevent the fire from reaching any explosives. If you are able to attempt this ensure that your water streams are placed between the fire and the explosives and attempt to work the fire away from the risk. Also ensure that any exposures that could conduct heat to the explosive storage areas are adequately cooled down. You might want to consider placing unmanned monitors in position to protect exposures and limit fire spread if it is an extremely high risk environment.
All this time, however, you must ensure that all crews committed to the operation must have an escape route. Continuously evaluate the movement of your crews and adapt the escape routes accordingly.
If the fire has reached the explosives, an immediate withdrawal must be implemented. The application of water will not extinguish them. All fire crews must be familiar with the pre-determined withdrawal alarm and this must be activated well in advance of any possible flame impingement on the explosives containers. It is here where the ‘RLH’ component of our tactical withdrawal has priority (RLH = Run like Hell).
If an explosion were to happen following your withdrawal, take care not to commit resources immediately thereafter. Structures could have become unstable and the possibility of secondary explosions cannot be ruled out. Only after consultation with the site representatives, explosives experts and other essential command staff can fire fighting be resumed.
Advice for operational crews
Crews involved in fire fighting and support activities must realise the unique dynamics of the incident they are dealing with. The most important of these will be to ensure that they are in constant communication with their sector and that this is maintained throughout the incident. Be careful, however, when working with radios inside the hot zone. No radio-frequency transmission is to be allowed within a ten-metre radius from an electro-explosive device. Vehicle mounted radios with an effective radiated output exceeding five Watt should not be allowed to transmit within 50 metres of the hot zone.
People must never work alone in the hot zone and should only enter the hot zone to do essential work. When identifying safe zones, bear in mind that single layer brick structures may afford little protection. Large explosives storage and manufacturing facilities usually have well established safety structures which will form part of your pre-planning map.
Incident termination
The incident command team will have to keep a tight rein on all activities and respond to any changes in the situation, finally bringing the incident to a successful conclusion.
Before terminating the incident and announcing an ‘all clear’, command should be satisfied that any residual hazards that may have developed during the operation have been dealt with and have been made safe. If the explosion caused a structural collapse and trapped people have to be rescued, it will be necessary to call in the department rescue squad or even the regional urban search and rescue team. Explosives experts and fire crews will then have to remain on scene while the collapsed structure is being delayered to ensure that no explosives products have remained that are able to cause an additional risk.
Notwithstanding the above, the incident commander should liaise with the department fire safety officer and any explosives inspectors and inform them of all his/her observations during the acute operational phase. These observations could be vital in determining the cause of the fire/explosion and provide helpful information on preventing further similar events.
South African law will require your service to hand the scene over to the police services and inspector of explosives following the incident termination.
In closing
I hope you have found this first article on the nine classes of hazardous materials valuable and interesting. I recall a large wildfire some years back where a 50-kilometre per hour wind was pushing the flames right up against a munitions warehouse. The fire service, assisted by helicopters, was able to prevent a major catastrophe by getting enough water between the fire and the building. This was only due to a strong incident commander and a well-established command system. The rapid decision making required for incidents involving explosives will require this.