Elsevier

Science & Justice

Volume 54, Issue 6, December 2014, Pages 412-420
Science & Justice

The ignitability of petrol vapours and potential for vapour phase explosion by use of TASER® law enforcement electronic control device

https://doi.org/10.1016/j.scijus.2014.04.004Get rights and content

Abstract

An experimental study was made of the potential of the TASER-X26™ law enforcement electronic control device to ignite petrol vapours if used by an officer to incapacitate a person soaked in petrol, or within a flammable atmosphere containing petrol vapour. Bench scale tests have shown that a wooden mannequin with pig skin covering the chest was a suitable representation of a human target. Full scale tests using the mannequin have shown that the arc from a TASER-X26™ is capable of igniting petrol/air vapours on a petrol-soaked person. Further tests in a 1/5 scale and a full scale compartment have shown that if a TASER is used within a compartment, a petrol vapour explosion (deflagration) may be achieved. It is evident from this research that if used in a flammable vapour rich environment, the device could prove fatal not only to the target but the TASER® operator as well.

Introduction

The present research was prompted by an investigation involving one of the authors(a) concerning a man who set himself on fire with petrol and died from burn injuries. The man had doused himself with petrol in his flat (room volume approximately 26 m3). Two police officers armed with TASER® weapons attended \he scene at the request of paramedics. However, before the officers were able to deploy TASER® to restrain the man, he ignited the petrol vapours using a cigarette lighter, sustaining fatal injuries.

The question subsequently arose of whether or not the officers could have ignited the petrol vapour by firing their TASER® weapons, possibly killing the man that they were trying to save, and even themselves.

A small number of incidents have been reported worldwide in which people have died as a result of burns sustained by individuals who caught fire at the time TASER® was used against them in the presence of petrol [1], [2], [3], [4], [5], [6].

The US National Institute of Justice (NIJ) has published research into deaths following Electro muscular disruption by Conducted Energy Devices (CEDs) [7]. The deployment of CEDs in a flammable atmosphere containing gasoline vapour is specifically cited amongst situations having a risk of moderate, severe or secondary injury. Published research on ignition of flammable vapours by TASER® devices is mainly concentrated around incapacitant ‘pepper’ type sprays [8], particularly Oleoresin Capsicum (OC) which contains the solvent methyl isobutyl ketone (MIBK), and 2-chlorobenzalmalononitrile (CS Spray) which contains ethyl alcohol (ethanol).

Further risk has been identified from use of TASER® in proximity to a number of explosive formulations, which are sensitive to electrical discharge. One such group is ‘organic peroxide explosives’ such as hexamethylene triperoxide diamine (HMTD) and triacetone triperoxide (TATP) [9].

The TASER®-branded device is an Electronic Control Device (ECD) [10] or otherwise referred to as a Conducted Energy Device (CED) or colloquially as a “stun gun” [11]. Its intended purpose is to assist with capturing, controlling, and restraining a person [10].

In the UK TASER® is classified among the “less lethal weapons”, defined in the UK as; “weapons, devices or tactics whose design and intentions are to induce compliance without substantial risk of serious or permanent injury or death” [12]. It is recognised that a sufficiently aroused and motivated individual might still be capable of performing dangerous acts of aggression including firing a weapon.

The TASER® delivers a high voltage, low-amperage current when barbed electrodes, connected to a battery-powered device, contact exposed skin or clothing of a subject. This electrical current interferes with the body's neuromuscular system, temporarily incapacitating the subject [13]. The TASER-X26™, as used by the UK police, is the model tested in this research. See Fig. 1.

The power source for the TASER® is a pair of 3-V lithium-ion cells [13]. A series of transformers and capacitors are used to increase the voltage from about 6 V to 2,000 V and finally to 50,000 V. At the same time the current is reduced from 4A down to 0.013 A [13].

When the trigger is pulled a compressed nitrogen-powered cartridge projects a pair of barbed probes (electrodes) (see Fig. 2), attached to 6.4 m (21 feet) long insulated steel wires, at 55 m per second. The barbs either penetrate the skin, by no more than 13 mm, or attach to target's clothing, and the electric current in turn travels down the wires. As the barbs get stuck in clothing and fail to reach the skin approximately 30% of the time [13], the device is designed to generate a brief arcing pulse. The arcing pulse ionises the intervening air to establish a conductive path for the electric discharge. The arcing phase has an open circuit peak voltage of 50,000 V (50 kV), which is only until the arc appears or until the barbs make contact with conductive flesh, at which point the voltage drops from 50 kV down to 1.2 kV. Once the barbs establish a circuit, the gun generates a series of 100 ms pulses at a rate of 19 per second (s) [15].

The TASER-X26™ device cartridges have an offset angle, which allows the top probe to be ejected horizontally in line with the laser sight and the lower probe to be ejected at 8° below the horizontal to allow for probe spread when it contacts the target.

In the UK the TASER-X26™ loaded with the “Live cartridge regular probe” [14] is currently the standard issue for police; see Fig. 2. The TASER-X26™ is held and fired like a conventional pistol. It is laser-sighted, and uses a single shot cartridge attached to the cartridge bay. The TASER-X26™ may also be used in direct contact with the target, with or without the cartridge attached, in a “drive stun” mode [12], [13].

The TASER® can be defined as a high voltage device according to British Standard BS7671:2008, [16] which defines high voltage as any voltage difference between conductors that is higher than 1000 V AC or 1500 V ripple-free DC.

Petrol is one of the most hazardous chemicals that the general public come into contact with. Petrol is formulated specifically for use in spark-ignition combustion engines. It is very easy to ignite, having high vapour pressure (it is extremely volatile), very low flashpoint (− 40 °C), and very low minimum ignition energy (MIE) of 0.24 mJ [17]. The Lower Explosible Limit (LEL) is 1.4% in air and the Upper Explosible Limit (UEL) is 7.6% in air [17], [18], [19], [20]). The vapour density is generally taken as between 3 and 4 times that of air [17], [18], [19], [20]. It is accepted that sparks or arcs from electrical equipment can ignite petrol vapours and any such equipment should not be used in hazardous areas [21], [22]. Note that automotive spark plugs produce an ignition voltage of between 10 kV and 30 kV [23].

The TASER-X26™ device produces 70 mJ of energy [24], nearly 300 times the MIE of petrol vapour, and therefore a TASER® arc is theoretically more than sufficient to ignite petrol vapours.

The UK Association of Chief Police Officers (ACPO) [25] issue guidance on the use and deployment of TASER® indicating eleven ‘Specific Risk Factors’, only one of which, 8.8, makes reference to flammable atmospheres.

The TASER® should not be utilised in an environment where, due to the presence of a flammable substance in the atmosphere or escaping gas, its use is likely to result in an even more hazardous situation. [25]

The current policy and training in the UK Police Service is to approve the deployment of TASER® where flammable materials are involved based on risk assessment. That risk assessment will take due regard to the threat from the individual against the Police officer and the availability of means to extinguish any subsequent fire [14].

There is apparently no previous research into the effects of TASER® deployment in an enclosed compartment containing flammable vapours such as petrol.

This study was designed in three parts:

  • a)

    Development of test apparatus and bench scale functional tests.

  • b)

    To determine whether or not the TASER-X26™ was capable of igniting a person who was doused in petrol, using a life-sized wooden mannequin partially covered with pig skin as a human simulant.

  • c)

    To determine whether or not deployment of a TASER-X26 in an enclosed room was capable of causing a petrol vapour explosion (deflagration), which might injure or kill all occupants of the room. These were carried out at 1/5 scale and then at full scale.

Note that the TASER-X26™ is classified in the UK under Section 5 of the Firearms Act 1968 [26]. Therefore the TASER® device was controlled and handled by a licensed TASER® operator at all times during these experiments.

Section snippets

Part a: development of apparatus and bench scale functional tests

The aim of this test series was to establish and confirm that the TASER device was capable of breaking down the electrical resistance of air thus initiating arcing between the barbs, in air, across pig skin and across a timber mannequin.

A series of initial bench scale tests were carried out using an insulated barb test apparatus. This was constructed to accurately measure arcing at set horizontal and vertical barb separations from each other and from a surface. Fresh pig skin and a wooden

Conclusions

A series of experiments was carried out to determine whether or not a TASER-X26™ was capable of igniting petrol vapour in the laboratory and in a practical, realistic confrontation situation.

This research has proved that the arc discharge from a TASER-X26™ is capable of igniting a simulated human target that has been doused with petrol. This was achieved by live firing at close range (1.6 m), and by manual placement of barbs to cause a “clothing disconnect” in which only one barb has penetrated

References (36)

  • J.D. DeHaan et al.

    Deflagrations involving heavier-than-air vapor/air mixtures

    Fire Safety Journal

    (2001)
  • Amnesty International

    ‘Less Than Lethal’?

    The Use of Stun Weapons in US Law Enforcement

    (2008)
  • G. Moran

    Lawsuit filed in fiery Taser-related death

  • The Associated Press

    Police investigating whether stun gun ignited Texas man who doused himself in gasoline

    (June 19, 2007)
  • J. Halpin

    As Taser use rises, so do questions about risks of fatalities

    The Fayetteville Observer (Fayetteville, North Carolina)

    (September 5, 2011)
  • L. Watling

    Police Taser fireball death to be probed

    The Express

    (April 27 2013)
  • US Department of Justice National Institute of Justice

    NIJ Special Report: Study of Deaths Following Electro Muscular Disruption

    (May 2011)
  • C. Myers et al.

    TASER safe, or flammable? Using pepper sprays with electronic control devices

    (2007)
  • Chief Inspector CMDU

    Police Service of Northern Ireland, Guidelines on the Operational use of Taser

    (2008)
  • R. Smith et al.

    Introduction: TASER ECDs, History, Electricity, Electrical Stimulation, Electrical Measurements, & Human Body

    (2008)
  • J.M. Cronin et al.

    Conducted Energy Devices: Development of Standards for Consistency and Guidance The Creation of National CED Policy and Training Guidelines

    (2006)
  • Association of Chief Police Officers

    Operational Guidance—Operational Use of Taser by Authorised Firearms Officers

    (2008)
  • Taser International Inc.

    TASER X26(tm) Manual

  • C. Sgt Milburn

    Firearms Trainer North Yorkshire Police

    Personal comm.

    (November 4 2010)
  • M.W. Kroll

    Crafting the perfect shock

    (December 2007)
  • British Standard BS7671:2008

    IEE Wiring Regulations: Requirements for Electrical Installations, Selection & Erection

    (2009)
  • D.J. Icove et al.

    Kirk's Fire Investigation

    (2009)
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