Explosives are generally categorised as those that:Deflagrate: a technical term describing subsonic combustion that usually spreads through thermal conductivity (hot burning material heats the next layer of cold material and ignites it). Deflagrations are usually less destructive than detonations, but still present a serious risk as they will generate an overpressure, which has the potential to harm individuals.Detonate: a process of supersonic reaction in which a shock wave is propelled forward due to energy release in a reaction zone behind it. In a detonation, the shock compresses the material, increasing the temperature to the point of ignition. The ignited material reacts behind the shock and propels the shock wave. Because detonations generate high pressures, they are very destructive.
Explosives, irrespective of whether they deflagrate or detonate, produce large quantities of hot gases and proceed without consuming oxygen from the surroundings. Ignited explosives can, for example, explode under water. Once initiated, the application of water will not extinguish a fire involving explosives.
The types of energy that can initiate explosives are:Impact/frictionFire/heatFragment attack/overpressureElectrostatic dischargeElectromagnetic radiation such as mobile phones, pagers etc (in the case of electro-explosive devices)Chemical reaction
For the purpose of transporting dangerous goods, explosives are defined as follows:Explosive substances: an explosive substance (or mixture) is a solid or liquid substance (or a mixture of substances) that is in itself capable by chemical reaction of producing gas at such a temperature and pressure and at such a speed to cause damage to surroundings. TNT and dynamite are known examples of explosive substances.Pyrotechnic substances: a substance (or a mixture of substances) designed to produce an effect by heat, light, sound, gas or smoke (or a combination of them) as a result of non-detonative self-sustaining exothermic chemical reactions. Pyrotechnic substances are commonly found in fireworks.Explosive articles: an article containing one or more explosive substances. For example, all kinds of ammunition.Pyrotechnic articles: an article containing one or more pyrotechnic substances or mixturesPhlegmatised (de-sensitised): a substance (or ‘phelgmatiser’) has been added to an explosive to enhance its safety in handling and transport. The phlegmatiser renders the explosive insensitive, or less sensitive to heat, shock, impact, percussion or friction. Typical phlegmatising agents include wax, paper, water, polymers (such as chloroflouropolymers), alcohol and oils (such as petroleum jelly and paraffin).
Multi-level injury from blast (blast injury) may result in impairments to groups of body organs and systems. A phenomenon called blast overpressure forms from the compression of air in front of a blast wave, which heats and accelerates the movement of air molecules. This overpressure phenomenon is considered to be the positive phase of the blast wave. The negative phase of the blast wave occurs later, as a result of sub-atmospheric pressure/under-pressurisation. The amount of damage from the pressure wave depends on the peak pressure, duration and medium in which the explosion occurs (open air, confined space, or water) and distance from the explosion.
The type of explosive will affect the nature and severity of the resulting blast injury. Explosives are categorised as either high-order or low-order.
High-order explosives are chemicals with a high rate of reaction. They include nitroglycerine, dynamite, C-4 (a common commercial and military explosive) and a mixture of ammonium nitrate and fuel oil. When a high-order explosive detonates, the chemicals are converted into gas at a very high temperature and pressure. High-order explosives can generate a large volume of initial pressure and a blast wave that may expand outwards in all directions.
Low-order explosives are designed to burn and gradually release energy at a relatively slow rate. These types of explosive are referred to as propellants because they propel an object, such as a bullet, through a barrel. Low-order explosives do not create the shock waves generated by high-order explosives. The blast wind of low-order explosives is a pushing effect rather than the shattering effect found in the blast wave of high-order explosives.
The effects of blast injuries are broken down into three distinguishable areas, these are:Primary blast injuries caused by the direct action of a blast wave on the body. The two most common injuries are eardrum rupture and lung haemorrhage. Lung haemorrhage is in fact the most likely cause of death in cases where primary blast effects prove fatal.Secondary blast injuries are defined as those that occur as a direct consequence of blast damage to buildings and structures. These injuries include lacerations caused by flying glass, blunt trauma caused by crushing and impact of falling masonry and suffocation caused by asphyxiating dust. Secondary blast injuries can occur at significantly greater distances from an explosion than either primary or tertiary blast injuries, and experience shows that structural collapse is the dominant mode of death and injury from explosions in built-up areas. Secondary blast injuries are normally related to the degree of building damage.Tertiary blast injuries are defined as those resulting from body movement induced by the blast wave. Two modes may be distinguished: injuries caused by differential displacement of internal body organs following high acceleration and injuries caused by impact when the body is either blown over or picked up by the blast wave and thrown against an object.
The constituents of explosives, especially fireworks, vary significantly; compounds such as metals, metal salts, chlorine donors, hydrocarbon fuels, and binders are incorporated into compositions for colour or sound effects, etc. Some of the constituents of fireworks are toxic. Unfortunately, literature relating to fireworks manufacture does not tend to cover this aspect in much detail. For example, most fireworks contain potassium perchlorate which in itself is an irritant to the mucous membrane and can adversely affect blood and the thyroid gland.
Severe burns may result even if no explosion takes place, as the ignition of some types of HD 1.3 and HD 1.4 explosives can result in a significant fireball. For example, the burst diameter of an aerial firework shell can be in excess of 100 metres. Lung damage may result if inhalation takes place.
Explosives generate considerable noise when they explode. This can cause hearing damage, usually a temporary loss of hearing, or ringing in the ears. Communication can be difficult especially if it happens over a protracted time with HD 1.4 fireworks, for example.
@gary_agg Not all the examples you give r good enough. Bursting tonnes of crackers in a matter of 5-6 hrs is indeed lethally & criminally polluting & so should be voluntarily shunned by the thinking people. Crackers are explosives. What have they— Droh Shankar (@SteamPoweredDM) Oct 24, 2020
There is a risk of entrapment following the collapse of a structure.
The majority of locations holding civilian blasting explosives are quarries. Explosives are typically held in a steel store. For quarrying operations most explosives are mixed on-site from non-explosive ingredients.
The Control of Major Accident Hazards Regulations 2015 (COMAH) apply mainly to the chemical manufacture and storage industry, but also to other industries where threshold quantities of dangerous substances identified in the Regulations are kept or used.
High explosives, or munitions using high explosives, are only manufactured at a few sites in the UK. Other sites and companies are engaged in manufacturing small arms ammunition, munitions, pyrotechnics, detonators and oil well explosives, amongst others. Explosives manufacturing of this nature is not a seasonal activity.
Most fireworks are sold and used during the peak firework season (October/November). However, professional firework displays take place at public and private events at other times of the year and a limited number of retailers sell fireworks all year round. Fire and rescue services could therefore encounter large stocks of fireworks at any time of the year.
Fireworks importation varies according to the time of the year and the special event for which the fireworks have been imported. For example, in 2006, approx. 1180 containers were brought through the port of Felixstowe, equating to 15,559 tonnes of fireworks (gross weight). Some 57% of these were received in August and September.
Fireworks display operators
Fireworks display operators are likely to be using HD1.1 and HD1.3 fireworks in addition to HD1.4. The main implications are:HD 1.1 presents a mass explosion hazardWhen fireworks of HD1.1 are present in a store together with HD 1.3 or HD 1.4 fireworks, the whole quantity will behave as if it is HD 1.1HD 1.3 articles do not present a mass explosion hazard; there is nevertheless a potential for them to explode and produce large fireballs
Note that while the UN HD definition states that HD 1.3 fireworks have no mass detonation, this is based on a test of the articles in the open within their correct transport or stowage packaging. Evidence from the Health and Safety Laboratory demonstrates that UN HD 1.3 fireworks will mass deflagrate (almost no perceptible difference to a detonation) when confined. In addition, containment presents a different reaction to that of confinement (e.g. ISO containers).
Shops and supermarkets usually only store small quantities of fireworks and then only during the peak firework season; these are kept either within the shop or in an IS0 container in the goods yard. Typically this will be up to 250 kg of HD1.4, or smaller quantities of HD1.3, but may be more if separation distances permit. Fire and rescue services should also be mindful of transient locations where explosives may be encountered and ensure that personnel are made aware of these. This may mean providing temporary mobilising information.
Improvised or home-made explosive devices
A concerning development in recent years is the increased manufacture and use of improvised or home-made explosives and explosive devices. These have many forms but the most common group are peroxide explosives (e.g. triacetone triperoxide (TATP), hexamethylene triperoxide diamine (HMTD) etc.).