Explosion Investigation – Process and Time Frame

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The main goal of any accident investigation, including explosions, is prevention. Determining the causes of an explosion and taking steps to eliminate or control them can help prevent similar incidents.

This article, which focuses on explosion investigation, attempts to provide an objective approach to systematically developing a set of pre-and post-accident actions for a successful accident investigation. This development primarily includes the steps investigators should take, the key questions that need to be answered, and what the investigation report should look like.

What’s an Explosion

An explosion is a large-scale, rapid, or spectacular expansion of energy or burst that can cause

  • Pressure differences
  • Shock waves
  • Seismic and thermal effects
  • Material projections into the immediate environment

The intensity of an explosion depends, among other things, on the following factors

  • What type of explosive material was used
  • How many explosives were detonated
  • Humidity and temperature at the time of the blast

Causes of Explosion

Explosions usually cannot be traced to a single factor. Inspectors must examine elements individually to determine their respective roles in causing the accident.

Which explosions need to be investigated

A qualified person must investigate all accidents, occupational diseases, and other hazardous incidents that may affect an employer’s employees. The accident investigation should determine the origins and causes of the circumstance.

This will allow the employer to take the necessary steps to prevent a recurrence. Accident inspections are designed to uncover all critical facts about how and why an accident occurred. Therefore, inspectors can prevent such an accident from happening again.

Investigation Steps

A successful explosion investigation begins with a consistent flowchart to uncover what happened to prevent future incidents. Every explosion investigation involves four steps that inspectors should systematically identify:

Origin – where the incident began

Fuel and ignition sources

Ignition sequence – the fire came first, or the explosion

Root cause

For example, when investigating Fires Involving Christmas Trees and Decorative Lights, the entire fire development must be characterized – from ignition to growth to extinguishment.

Investigation Questions

It is vital to know precisely what to do in the event of an accident or occupational disease.

The first step in investigating an accident is thinking about it and developing an exploratory action plan. This first step occurs before any incident and begins with answering critical questions about the investigation:

Who should lead the inspection, and who will participate?

How should the information be recorded?

What tools and requirements will be needed for the assessment?

What procedures will be followed during the inspection?

Every standard company should have a health and safety program that specifies who should conduct the accident investigation and what training that person must have.

Forensic Engineering Investigation

In any explosion investigation, the classic question is, “What came first?” In forensics, the initiating event is called the “origin.” The “cause” is derived from the combination of contributing factors that led to the incident.

A promising forensic engineering inspection will elucidate where they went wrong, whether a machine, process or human. An explosion inspection is a four-step process; the first step is to find the “source,” the place where it started.

Creating an accident inspection kit is necessary. An accident inspection kit is a prepared box that contains the forms, tools and materials needed for an inspection. It might include the following:

  • Pens
  • Paper
  • Camera
  • Flashlight
  • Tape measures
  • Audio/video recording devices.

If resources permit, the inspection may include a laptop with special programs and software to help track witness testimonies. Inspectors can then act quickly by grabbing the kit and starting their work.


Investigations should begin ASAP after the explosion and be completed soon as possible. If there is a delay, virtual evidence may disappear, and witnesses’ memory may deteriorate over time.

The sooner an accident investigation is completed, the sooner employers can make changes and corrections to improve worksite safety. Sometimes on-site investigations end relatively early; this is just the beginning of what is likely to be a very long investigation. Inspectors should gather relevant information about what happened before and during the incident.

Investigators should perform three tasks to make the accident investigation a valuable tool in preventing an incident:

  • The information gathered must be analyzed
  • Employers must take corrective action
  • Employers must monitor the effectiveness of the measures

They can then determine the circumstances of the incident by interviewing witnesses and examining physical evidence to explain why and how an accident occurred. These tasks are of equal importance and should be completed as soon as possible to ensure a complete accident investigation.

In addition, it is equally important to document the steps taken immediately after the incident to deal with the emergency and initiate the investigation. The forms to be used and the procedures to be followed should also be agreed upon within the allotted time frame.

Recording & Reporting

The first and most crucial step in an investigation is identifying the injured persons. Administrators must secure the accident site once the casualties have been cared for. In this way, the inspection process and anything related to the incident should remain undisturbed.

  • An explosion inspection includes
  • The scene
  • All equipment involved
  • Policies and procedures in the workplace
  • Worker training history and records

Health and safety inspectors should thoroughly interview witnesses, including employers, co-workers, supervisors, and anyone else who may have pertinent information.

Human Error

The primary purpose of an explosion investigation is to prevent future accidents rather than to apportion blame. But what if human error, either by a worker or management, is critical to the incident? If human error is relevant, it must be mentioned in the investigation report. Omitting it would distort the testimony and undermine its effectiveness.

The key is how to present the role of human error. First, investigators should never recommend disciplinary action or reprimand in their report because that is not the purpose of the investigation. Once the analysis is complete, an employer can consider whether discipline is warranted.

Second, the report should document the course of events in chronological order as neutrally and objectively as possible to avoid implicit blame. The documentation should provide context for the failure by reporting why and how the mistake was made – for example, lack of training, unclear processes, or time pressure.

This can also be made by referencing broader dynamics in the workplace – for example, that safety was not prioritized. Few people should not be singled out for corrective action in the detailed reports.

Investigators should slant their recommendations and suggestions. For example, writing, “Person A needs more training because he or she should not have performed action B.” is less effective than, “This incident reminds us of one in which person X had better not forget action B.” The latter wording should also indicate that a single failure is due to broader systemic problems, and therefore address those systemic issues more explicitly.

All explosion events most likely involve a human component to some degree. The view of the broader and probably more significant factors that caused the incident should be correctly reported. Reporters may not release some technical details about the explosion or the investigation. Investigators need to be aware of bias and ensure that their actions or reports are not crafted to fit the preference.

Investigators’ Duties

Who will investigate an incident? This is a fundamental question. It won’t be just one person; a lead investigator should be a team. The lead should have unmatched investigative experience and knowledge of operations.

Many companies tend to assign a senior manager or a senior health and safety officer to lead the investigation of an incident. No one will successfully investigate an incident alone, and investigators should bring in others to assist, share the workload, and bring different perspectives.

Investigators use GPS and aerial photographs to find and track each incident. They examine surveillance video, interview witnesses, and create a timeline of what happened before the blast.

However, processing the documentation could take weeks or months under complex circumstances. The materials that caused the explosion will likely determine what triggered the accident.

A common investigative trend would be to look for signs of heat damage or locations where excessive heat may have been applied. Investigators will also look for metallic, solid, and electronic components.

Depending on their training, experience and technical expertise, they’ll try to solve the puzzle, e.g., whether an item is a component of an automobile or an electronic device that triggered the incident.

Investigation Team

Other potential participants may include:

  • Occupational Health and Safety (OHS) Committee members
  • Other employee representatives
  • Individuals associated with the work
  • Direct supervisor of the work

However, there are some instances where supervisor involvement is not appropriate.

Sabotage Explosion

Whether the device’s designer used readily available materials or military equipment may help investigators narrow the search. Whether they used “low” or “high” explosives can also be very helpful.

Investigators may find evidence of commonly available materials, such as those used in pipe bombs. Criminals may purchase these improvised explosive devices at hardware stores. Investigators may also find smokeless or black powder used in a handgun or rifle ammunition.

Alternatively, investigators may search for a suspect if the originator used hard-to-find materials or “high” explosives. Investigators focus their attention on what is known as the seat of blast and the area of most significant damage.


Once an accident occurs, it’s of utmost importance to care for injured employees, evacuate those at risk, and secure the scene. There are several types of hazardous events, including the following:

Minor Injury

A minor injury is an occupational disease or accident that provides some medical treatment and precludes disability. “Medical treatment” refers to medical treatment in a medical clinic, doctor’s office, or hospital. 

Medical administrators may provide emergency medical treatment at these locations, and medical treatment is not to be confused with first aid.

Disabling Injury

A disability injury is an occupational disease or accident that results in an employee’s inability to perform their former duties. Disability injuries may be temporary (sprained wrist) or permanent (severed limb), depending on whether or not the worker is expected to make a full recovery.

Loss of Consciousness

This type of injury can be caused by burns, electric shock, lack of oxygen, or a toxic atmosphere.

Emergency Response Plan

Explosion investigators should perform rescue and resuscitation procedures. Emergency procedures must be implemented for each incident, such as hazardous materials spills, violence prevention, or bomb threats.

This step should closely align with the emergency plan and be performed by emergency responders. Securing the scene involves two measures. First, employers should remove any uncontrolled hazards (e.g., leaking gas) to ensure the safety of investigators and others.

Second, investigators should protect the scene so that witness statements cannot be intentionally or unintentionally destroyed or altered until the accident is investigated. This protection usually includes restricting access to the scene, as you may have seen in movies.

The protection operation may also require that the scene be protected from inclement weather.

How About Small Enterprises

The investigation process is often complicated and highly technical. It’s doubtful that a small charity or retail store has the resources, e.g., infrastructure or budget, to form an experienced investigation team, including health and safety teams.

In other words, there are most likely few resources that employers can leverage to develop accident investigation capabilities. Therefore, accidents in small businesses are less likely to result in effective preventive measures.

Get In Touch

If you need fire and explosion investigation services, contact us today. Our experts have the technical knowledge and experience to analyze any complex Explosion investigation – Process and time frame.