When a collision involves a truck transporting highly flammable substances such as propane, butane, or liquid petroleum gases, it can pose significant danger. These materials are recognized for their high explosiveness, and a collision can lead to fire outbreak or even an explosion. It is crucial to avoid approaching, observing, or capturing footage of a collision involving a truck carrying such hazardous substances, as it can be extremely hazardous. The recent occurrence in Boksburg serves as a poignant reminder of the severe consequences that can ensue if these hazards are not taken seriously.
In the event of such a circumstance, it is imperative to maintain a safe distance, immediately contact emergency services, and comply with their directives.
The explosion’s pressure wave and heat can result in severe burns, injuries, or fatalities for individuals in proximity to the blast. Furthermore, the chemicals and gases released during a fire or explosion can have harmful effects on humans, animals, and birds, as well as inflict lasting harm on the environment.
In the instance of Boksburg, a truck became wedged underneath a bridge. After some time, a fire ignited, subsequently spiraling out of control and resulting in a BLEVE explosion, claiming the lives of those in the vicinity, including onlookers and individuals recording the incident. At the time of writing this article, the fatality count had escalated to 40 individuals.
A boiling liquid expanding vapor explosion (BLEVE) is a form of explosion that arises when a pressurized container holding a liquid at or above its boiling point undergoes a sudden reduction in pressure. This occurrence can arise in various circumstances, including instances where a pressurized tank carrying a combustible liquid like propane or butane sustains punctures or ruptures.
Upon the container experiencing a sudden drop in pressure, the contained liquid promptly begins to boil and enlarge, generating a considerable amount of vapor. The heightened pressure resulting from the vapor buildup can culminate in the rupture or explosion of the container, leading to an immense discharge of energy. This vessel rupture can result in the emergence of projectiles, burn, blast waves, and toxic gases, which may inflict substantial harm on nearby buildings and vehicles, as well as cause severe injuries and fatalities to individuals.
BLEVEs pose significant danger as they can transpire unexpectedly and discharge a vast amount of energy in a brief span. The resulting pressure wave and heat from the explosion can inflict severe burns, injuries, and even prove fatal for individuals in close proximity to the blast.
Moreover, it is crucial to be acquainted with emergency evacuation protocols and ready to adhere to them if an incident occurs when in the proximity of a facility that stores or employs pressurized containers of flammable liquids. Furthermore, if inside a vehicle, it is advisable to remain in the vehicle with closed windows and the AC/Heater turned off until the occurrence is resolved, or the emergency services have authorized the clearance of the area.
For instance, Butane and Methane are hydrocarbons composed of hydrogen and carbon. The following are some of their technical characteristics:
- Molecular formula: C4H10
- Boiling point: -0.5 °C (31.1 °F)
- Melting point: -138.4 °C (-216.1 °F)
- Density (at 20 °C, 1 atm): 2.48 kg/m³
- Specific gravity (at 20 °C): 0.582
- Flashpoint: -11 °C (12.2 °F)
- Autoignition temperature: 446 °C (835 °F)
- Molecular formula: CH4
- Boiling point: -162 °C (-259 °F)
- Melting point: -182.5 °C (-298.5 °F)
- Density (at 0 °C and 1 atm): 0.717 kg/m³
- Specific gravity (at 15.6 °C): 0.554
- Flashpoint: -161 °C ( – 258 °F)
- Autoignition temperature: 537 °C (999 °F)
It is essential to consider that these characteristics may vary depending on the specific measurement conditions of the substances. Moreover, it is worth noting that despite both being hydrocarbons, they exhibit different behaviors. Butane, for instance, is a highly volatile substance and is commonly utilized as a fuel source for portable gas heaters, camping stoves, and lighters. On the other hand, Methane is utilized as a fuel source and is a vital constituent of natural gas, which is used to generate heat and electricity.
The blast radius resulting from a BLEVE is influenced by multiple factors, such as the size and pressure of the pressurized container, the characteristics of the liquid or gas stored in the container, and the surrounding conditions. The quantity of the substance involved in the incident is among the most critical factors in determining the blast radius of a BLEVE.
In order to determine the blast radius of a BLEVE, multiple models and equations are utilized, which rely on factors such as the characteristics of the explosion, the properties of the substance, and the geometry of the container. These models take into account various factors, including the amount of gas or liquid stored, the pressure contained within the container, the shape and size of the container, and the specific properties of the gas or liquid.
In an illustrative scenario, consider a cylindrical pressurized container with a volume of 60,000 liters, containing propane up to 80% of its liquid capacity. To determine the blast radius, the following calculations can be made:
- Step 1: To determine the energy of the explosion, it is necessary to consider the energy value of propane, which is approximately 2.5 KJ/g. If the pressurized container has a volume of 60000 litres and contains propane at 80% of its liquid capacity, then the total energy of the explosion can be calculated as follows: 2.5 x (60000 x 0.8) = 900,000 KJ.
- Step 2: To determine the overpressure generated by the explosion, we need to calculate the ratio of the maximum pressure to the atmospheric pressure. This can be achieved by using the formula P = E/V, where P represents the pressure, E represents the energy of the explosion, and V represents the volume of the cylindrical container. Based on this formula, the estimated overpressure can be between 15-20 kPa.
- Step 3: To determine the blast radius, the following formula can be used: R = (P/r)^1/3, where R is the blast radius, P is the overpressure, and r is the density of air (1.225 kg/m³). Based on the calculated overpressure of 15-20 kPa, the blast radius can be estimated to be around 31-35 meters.
It is important to acknowledge that these calculations are approximate, and the actual blast radius may differ depending on the specific circumstances of the incident. Additionally, the aforementioned calculation does not account for structural and topographical factors at the incident site, which can impact the blast radius.
To minimize the risk of death or serious injury in the event of a BLEVE, it is crucial to maintain a safe distance from the pressurized container. According to the Emergency Response Guidebook 2020, a recommended evacuation radius of at least 1.5 km and a preferred evacuation radius of up to 2.2 km from the site of the BLEVE incident can help minimize the risk of injury or death.
Based on this illustration and in accordance with the Emergency Response Guidebook, the following observations can be made:
- The Blast (Fireball) radius, circled in red, is approximately 77m.
- The EMS distance – the closest that Emergency Services should be from the scene is approximately 306m.
- The minimum evacuation distance, circled in green, is the area that should be evacuated, for safety.
- The ideal area that should be evacuated is about twice that – the area outside the green circle.
- The Thambo Memorial Hospital (Pin 1) is within the EMNS distance, and very close to the blast area.
- The Boksburg Police Station (Pin 2) is only 560m away – well within the minimum evacuation zone.
- The Boksburg Fire Department (Pin 3) is only 790m away – well within the minimum evacuation zone.
- The Ekurhuileni Metro Police Office (Pin 4) is only 970m away – also well within the minimum evacuation zone.
- Even the Ekurhuleni Municipal Buildings (Pin 5) is only 930m away – well within the minimum evacuation zone.
Individuals who are exposed to a BLEVE explosion at close proximity, i.e., within the inner red circle, may suffer from a variety of injuries depending on their distance from the explosion, their protective gear, and the characteristics of the blast. The following mechanisms of injury and causes of death are likely for individuals exposed to a BLEVE explosion at close range:
- Burns: A BLEVE explosion can generate intense heat and flame that can result in severe burns to the skin and internal organs. The extent of burns can range from first-degree to third-degree burns and may prove fatal if they cover a significant portion of the body or affect critical areas such as the face, airway, or vital organs.
- Blast trauma: A BLEVE explosion can generate a pressure wave that leads to various types of traumatic injuries, including blunt trauma, lacerations, fractures, and dislocations. These injuries can occur due to the force of the blast wave, being hit by flying debris, or being crushed by collapsing structures.
- Asphyxiation: A BLEVE explosion can result in the release of toxic gases such as carbon monoxide and hydrogen cyanide, which can lead to asphyxiation and suffocation. These gases can displace oxygen in the air, thereby causing difficulty in breathing for individuals exposed to them. Furthermore, prolonged exposure can cause brain damage or even result in death.
- Projectile injury: The force of the blast during a BLEVE can produce projectiles, including broken fragments of the container, equipment, or debris. These projectiles can travel at high speeds and result in severe injuries such as lacerations, fractures, or penetrating wounds.
- Cardiac Arrest: The psychological and physical trauma caused by a BLEVE explosion can be so severe that it may trigger cardiac arrest in some individuals.
- Dismemberment: The magnitude of the shockwave resulting from a BLEVE incident is so extreme that individuals within the immediate blast radius (less than 77m) may suffer dismemberment. This was exemplified in the Boksburg incident where a hand was discovered in a nearby tree several days after the explosion.
It is important to emphasize that the aforementioned mechanisms of injury and causes of death are not exhaustive, and the nature and severity of injuries can vary depending on the specifics of the BLEVE incident. The most effective means of preventing such injuries is to maintain a safe distance from pressurized containers and avoid approaching or filming the site of an accident involving these containers.
Below are some general guidelines for providing medical care to individuals who have sustained severe injuries as a result of a BLEVE explosion:
- Immediately calling for emergency medical assistance is the most crucial step and should be taken without delay.
- Assess the person’s responsiveness and pulse. If the person is unresponsive, initiate CPR if properly trained.
- In order to provide appropriate care, it is crucial to assess the person’s injuries caused by a BLEVE explosion, which can vary from burns to traumatic injuries.
- In cases of traumatic injuries, such as fractures or dislocations, it is important to immobilize the affected area to avoid exacerbating the injury.
- In case of a suspected inhalation injury, promptly relocate the individual to an area with adequate ventilation and monitor their breathing.
- Take into consideration the possibility of exposure to toxic gases or chemicals and implement adequate safety measures to safeguard yourself and the patient.
- If you detect any chemical odors, it indicates that you are in close proximity to the source and it is crucial to evacuate yourself and any patients immediately, even prior to the onset of a fire.
It is important to note that the aforementioned guidelines are general and the treatment provided should be tailored to the specific circumstances and conditions of the patient. Additionally, it is crucial to recognize that first aiders must adhere to their level of training and follow the protocols established by local emergency services.
It is crucial to keep in mind that BLEVE explosions are extremely hazardous events that can result in serious injuries and fatalities. The most effective way to prevent such injuries is to avoid pressurized containers and refrain from approaching or recording the scene of an accident involving these containers.
In the event of a truck accident involving propane or butane gas, it is crucial to contact emergency responders immediately by calling 10177, 10111, 084 124, or 112. When making the call, dispatchers will require specific information to ensure the appropriate response is deployed to the accident scene. The following is a list of the information that will be needed by dispatchers when calling for emergency assistance:
- Provide the accident location details, including the street address or nearest intersection, and any nearby landmarks or reference points.
- The number of vehicles involved in the accident
- Provide a detailed account of the accident, including the severity of the incident, the extent of damage to the involved vehicles, and the magnitude of any propane or butane gas leakages.
- Any reports of injuries or fatalities resulting from the accident should be provided to the emergency responders when calling for assistance.
- Provide a detailed description of the truck and its cargo, specifying the type of gas being transported, and the size of the container or tanker involved in the accident.
- Provide information on any fires or explosions that may have occurred, as well as the current status of the fire.
- Please provide information about whether people have been evacuated from the area and if not, the number of individuals present in the immediate vicinity.
- Please provide your name and contact information for any follow-up questions.
Remaining calm and speaking clearly when providing information to the dispatcher is crucial. Following their instructions and providing accurate and timely information can help emergency responders to effectively respond to the accident and reduce the risk of injury or loss of life.
In the event of an accident involving chemicals, it is crucial not to leave the area until emergency services arrive and instruct you to do so. It is essential to keep a safe distance from the scene and avoid approaching it to allow emergency responders to perform their duties.