Many seemingly ordinary materials may lead to an explosion in the workplace. The essential health and safety requirements presented in DSEAR (Dangerous Substances and Explosive Atmosphere Regulations) and ATEX (Atmosphere Explosive) directives call for an integrated approach to explosions.
On top of employing necessary prevention methods, directives ensure that conditions under which an explosion becomes possible do not occur. They also develop and implement protection methods to minimize the effects of an explosion. The main objective is to protect people from fire and explosion hazards related to hazardous substances and possible explosive atmospheres.
We put forward one of our previous blogs: “Fire Hazards– Examples and Prevention Tips,” along with the present article to help businesses provide a safe and secure workplace.
Why Fire & Explosion Occur
When flammable and combustible materials in the form of gasses, liquids, and solids have a sufficient vapor concentration in a particular atmosphere, an explosion can occur either by heat ignition or autoignition. Explosive liquids include
- Paints
- Gasoline
- Propane
- Butane
- Airborne dust
- Thinner
Elements Of Dust Explosion
Ingredients needed for a fire or “Fire Triangle” in a workplace are:
- Combustible dust (fuel)
- Ignition source (heat)
- Oxygen in the air (oxidizer)
The most natural and synthetic organic materials and some metals can form combustible dust. Additional elements required for a dust explosion:
- Dispersion of dust particles in sufficient concentration
- Confinement of the dust cloud
The addition of these two components to the fire triangle creates what’s known as the “explosion pentagon.” If something ignites a dust cloud (diffused fuel) within a confined or semi-confined vessel, building, or area, the result can be disastrous.
In this case, fuel rapidly burns and can even explode. The ensuing fires will then threaten the safety of employees by further explosions, flying debris, and collapsing building components.
An initial explosion in processing equipment or in an area where fugitive dust suspends in the air may release more Combustible dust or damage a containment system (such as a duct, vessel, or collector).
Therefore, if ignited, the additional dust dispersed into the air can probably cause one or more subsequent explosions. The secondary explosions may be much more devastating than the first one because of the amplified quantity and concentration of dispersed combustible material.
If an element of the explosion pentagon is missing, an explosion cannot occur. Note that two elements in the explosion pentagon are challenging to get rid of.
- Oxygen (within the air)
- Confinement of the dust cloud
However, the other three elements can be controlled significantly and will be discussed further.
Flash Point
Fire and explosion occur when the temperature of a volatile substance reaches its flash point and where there is sufficient oxygen present in the atmosphere.
If you don’t know, a flashpoint is a temperature at which a particular compound gives off sufficient vapor to ignite in the air.
Dust Combustibility
The primary factor in assessing fire hazards is whether the dust is combustible. Any “material that burns in the air” in a solid form can be explosive in a finely divided form. We can define combustible dust as: “Any finely divided solid substance with a diameter of 420 microns or smaller that presents a fire or explosion risk when dispersed and ignited in air.”
Many natural or synthetic substances can form combustible dust, including some metals. It primarily depends on particle shape, size, and moisture content. Furthermore, these variables can change while the material passes through process equipment.
Hence, published tables of dust explosibility data may be of limited practical value.
In some cases, dust clouds will be combustible even if the particle size is more significant than specified in the NFPA definition, especially if the substance is fibrous.
Industrial settings can involve high-energy ignition sources like welding torches. In such cases, test methods for dust ignition and explosion characteristics from ASTM International (the American Society for Testing & Materials) can be of value.
Autoignition
Autoignition is the lowest temperature at which a concentration of a flammable or combustible material spontaneously ignites in a typical atmosphere without an external ignition source, such as a flame or spark. This temperature is needed to supply the activation energy required for combustion.
Fire & Explosive Safety Hazards
Every workplace with dangerous materials and workplaces that perform hot work must comply with standards and regulations. An employer must ensure that the following standards are always met.
- Safe work procedures
- Distribution of sufficient fire extinguishers and other fire protection equipment in the workplace
- Using safe substances to start a fire
- Storing flammable materials and containers with standard documentation.
- Control of ignition sources and static charges
- Not entering workplaces where a flammable or explosive substance is present in the air at a level more than 10% of the lower explosive limit of that substance.
- Purging with effective removal methods is performed before any hot work begins on pipes or containers containing flammable substances.
- Proper storage of compressed gas equipment
- Training workers in identifying fire and explosive hazards and encouraging them to report unsafe conditions so immediate action can be taken.
Employers must develop and implement safe procedures when working with combustible liquids, flammable substances or performing hot work; they should train workers on those safe work procedures to ensure compliance with those procedures.
Further tips:
- Follow standard and safe work procedures for fire and explosive risks, including hot work if you’re performing hot work in the workplace.
- Train employees in safe work procedures
- Ensure your employees comply with safe work procedures
Dangerous Substance
Suppose you don’t correctly utilize, store, or control dangerous substances. They can harm people and cause a fire, explosions or similar incidents, like chemical reactions that can produce enormous heat and energy. Fire and explosion hazards include dust, explosive substances and electrical equipment.
Dangerous substances could threaten people’s safety and possibly expose them to fires, explosions, or similar incidents, e.g., “thermal runaway” (chemical reactions producing heat.) It’s easy to overlook common safety hazards with so many demands and factors to consider– even for those who consider the subject a top priority.
Liquids, gasses, vapors and clouds of dust that may be present in a workplace can all be hazardous substances. Some examples of items you should look out for include:
- Solvents, such as acetone, toluene, diethyl ether
- Flammable gasses such as acetylene, hydrogen, propane
- Paints & varnishes
- Liquefied petroleum gas (LPG)
- Clouds of dust from machining & sanding operations
Explosive Atmosphere
We define an explosive atmosphere as a mixture of an unsafe substance (mist, gas, dust, or vapor) with air that can potentially ignite or explode. In addition to fire and explosion events, this definition also applies to other energetic incidents such as decompositions of unstable substances (e.g., peroxides) or runaway exothermic reactions.
Facility Dust Hazard Assessment
Any industrial method which reduces a combustible material and some non-combustible materials to a finely divided condition presents a potential for a severe fire or explosion. It’s worth noting that the potential risk of combustible dust explosion may exist in various industries, including the following.
- Food (e.g., candy, starch, flour, feed)
- Plastics & rubber
- Wood & furniture
- Textiles, pesticides, & pharmaceuticals
- Metals (e.g., aluminum, chromium, magnesium, iron & zinc)
- Dyes & coal
- Additive manufacturing & 3D printing
- Fossil fuel power generation
Facility Analysis Components
Facilities have to carefully recognize the following to assess their potential for dust explosions:
- Materials that can be combustible when they’re finely divided
- Potential ignition sources
- Methods that use or consume combustible dust
- Open sites where combustible dust may build-up
- Hidden areas where combustible dust may accumulate
- Equipment that disperses explosive substances in the air
Importance of Understanding Explosion Hazard
Employers must protect their employees and workers from fire and explosion risks. The following incidents clearly explain the importance of taking safety measures.
Organic Dust Fire & Explosion: Massachusetts (Three Killed, Nine Injured)
In February 1999, a massive fire and explosion took place in a foundry in Massachusetts. The Occupational Safety Health Administration (OSHA) investigated this fatal event. Its report indicated a fire initiated in a molding machine from an unknown source and then extended into the ventilation system by feeding heavy phenol-formaldehyde resin dust deposits.
A small primary deflagration took place within the ductwork, dislodging dust that had settled on the exterior of the vents. The resulting dust cloud then provided fuel for a violent secondary explosion to lift the roof and cause wall collapses and failures. The factors listed in the report included inadequacies in the following areas:
- Housekeeping to control dust accumulation
- Ventilation system design
- Maintenance of ovens
- Equipment safety devices
Organic Dust Fire & Explosion: North Carolina (Six Killed, 38 Injured)
In January 2003, major fires and explosions destroyed a pharmaceutical manufacturing plant of rubber drug-delivery components in North Carolina. Six workers were killed, and 38 individuals, including two firefighters, were seriously injured.
The CSB (Chemical Safety & Hazard Investigation Board), an independent US Federal agency, investigated this chemical incident. It concluded that the addition and accumulation of combustible polyethylene dust above the suspended ceilings fueled the deadly incident.
The CSB could not track down what ignited the initial fire or how the combustible dust was dispersed, leading to an explosive cloud in the hidden ceiling space. The explosion caused considerable damage to the plant and did minor damage to nearby businesses, homes, and schools. The causes of the incident include inadequacies in the following sections.
- Hazard assessment
- Hazard communication
- Engineering management.
The CSB recommended implementing provisions in the National Fire Protection Association standard and the formal application of this standard by North Carolina.
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Organic Dust Fire & Explosion: Kentucky (Seven Killed, 37 Injured)
In 2003, another deadly dust explosion occurred in a Kentucky acoustics insulation manufacturing plant. The CSB investigated this incident as well, reporting a likely ignition scenario. Initially, a small fire started from an unattended oven.
It then ignited a dust cloud created by nearby line cleaning. And eventually, a deadly cascade of dust explosions occurred throughout the place. The CSB determined several causes of ineffective dust control and explosion prevention (mitigation), including inadequacies in the following sections.
- Hazard assessment
- Hazard communication
- Maintenance procedures
- Building design
- Investigation of previous fires
Metal Dust Fire & Explosion In Indiana (1 Fatality; 1 Injury)
Finely dispersed airborne metallic dust can also lead to explosion when confined in a vessel or building. In 2003, a plant in Indiana machining auto wheels experienced an incident that the CSB later investigated.
A report has not yet been issued. However, a CSB news release described the story as the previously discussed organic dust accidents. Aluminum dust was included in a primary explosion near a chip melting furnace, followed by a secondary blast in dust collection equipment.
Related Incidents In The Grain Handling Industry
In the late 1970s, devastating dust explosions in grain elevators left 59 people dead and 49 injured. Addressing these fatal events, OSHA issued a “Grain Elevator Industry Hazard Alert,” providing employers, employees, and other staff with information on the safety and health risks associated with the storage and distribution of grain.
In 1987, OSHA announced the Grain Handling Facilities standard, which remains effective. This benchmark, other OSHA standards such as Emergency Action Plans, and updated industry consensus standards all played an essential role in reducing the occurrence of explosions in this industry and mitigating their effects.
The lessons taught from the grain industry can be applied to other industries producing, generating, or using combustible dust.
Controlling Fire & Explosion Hazards
Identify fire and explosion risks for work areas, including:
- Potential ignition sources
- Dangerous compounds, such as those formed in the workplace
- Potential accumulation and possible extension of explosive atmospheres
- Work procedures involving the dangerous substance.
Evaluate the hazards associated with identified fire and explosion hazards. Undertake a fire or explosion hazard assessment using standard templates and procedures, with due attention to:
- Substances, their amounts, work processes utilized and their possible danger
- Risks associated with the use of more than one dangerous substance in combination
- Arrangements for safe handling, storage and transport of hazardous substances. Eliminate or mitigate risks where reasonably practical, and apply a hierarchical approach. Consider the following when doing so.
- Use a different work process where you can considerably reduce the risk of explosion or fire.
- Work with substances that aren’t classified as dangerous.
- Utilize less dangerous compounds, for example, those with higher flashpoints
What’s Next?
Now it’s time to develop control measures to prevent fire, explosion or similar energetic events, prioritizing as follows:
- Avoid ignition sources
- Reduce the number of dangerous compounds to a minimum
- Avoid or minimize the release of hazardous substances
- Control releases of dangerous compounds at the source
- Prevent the formation and accumulation of an explosive atmosphere; observe the ventilation system in particular
- Keep incompatible chemicals apart
- Collect, contain, or eliminate any releases to a safe place
- Avoid severe conditions with exceeding pressure or temperature that could lead to danger
Implement mitigation processes to reduce the detrimental effects of a fire, explosion, or similar incident using the following tips:
- Provide suitable personal protective equipment (PPE)
- Reduce the number of workers exposed to danger
- Provide a burst-resistant plant
- Provide explosion suppression or explosion relief equipment
- Take measures to control or reduce the spread of fires or explosions
Put proper arrangements to prepare for accidents, incidents, and emergencies. Think about:
- Need for any additional first aid tools
- Other safety training required, tested
- Providing any equipment or clothes for persons dealing with an incident
- Providing appropriate communication systems such as alarms, warning signs, warning lights or Tannoy systems
DSEAR Directives
The DSEAR, short for Dangerous Substances and Explosive Atmospheres Regulations, requires workers to assess the hazards of explosive incidents that dangerous substances in the workspace may cause. These hazards should then be eliminated (or at least reduced).
The regulation may apply to the including:
- Use of flammable solvents in laboratories
- Transporting flammable substances in vessels around a workstation
- Use of combustible gasses, such as acetylene, for welding
- Handling and storage of combustible wastes such as fuel oils
- Handling gasses under pressure
- Handling substances corrosive to metal
What To Do In An Emergency?
Understand and practice emergency procedures to know the basics of safe-handling the situation:
- Ensure that proper fire extinguishers are available for use.
- Be aware of at least two different exit paths in a fire incident.
- Follow control procedures and have sufficient equipment ready (e.g., personal protective equipment, absorbent control materials, non-sparking tools, etc.).
- Immediately report leaks to your employer, warn people in the area, and quickly move to a safe location.
Bottom Line
A devastating fire or explosion may result from the rapid combustion of flammable gas, dust, or powder. Flammable vapor, mist, or flammable liquid can also cause a fire. You might think of explosions as unlikely threats, but we provided some examples to illustrate that they could happen to you too.
Therefore, it’s vital to select the proper prevention and protection techniques. We offer comprehensive Fire & Explosion Investigation Services, enabling our consumers to firstly record the reasoning behind the prevention techniques and control fire and explosion hazards as much as possible.
