Some of the biggest concerns in occupational safety are how to prevent and, if and when they do occur, deal with and manage fires and explosions.
While this document is by no means intended to be a source of expertise, and neither the author nor African Technology Forum claim or offer any expertise in these areas, it is intended to point to at least some available references and learning materials dealing with these issues.
As with our energy hazard control and lockout article, this article deals with the unintentional release of energy. However, here the release can not only be rapid, explosive, and fatal, but self-sustaining, feeding on more and more material, fueling it on to greater and greater destruction. The following material will deal with fires specifically. A follow-on article will cover explosions themselves.
Types of fires and their extinguishers
Fire classifications are based on fuel type or energy source. Extinguishers and the extinguishing agents particular to each type of fire all have the basic job of cooling the fire, blocking further oxygen from driving the combustion, blocking the burning material from further fueling the fire, and stopping any further chemical reactions driving the combustion.
While the physics are the same, across the globe the nomenclature of fire and extinguisher classifications may change. In the United States, for instance, the five classes of fire, and the general methods of extinguishing them, are:
- Class A: Ordinary combustible materials, such as wood, paper, cloth/textiles, and rubber and plastics. Class A extinguishers work by cooling the fuel by absorbing the heat via an agent like water or coating it via a dry agent like powder.
- Class B: Flammable liquids, those with flash points (where their vapors in air can ignite) below 37.8°C (100°F) and therefore very dangerous at room temperature, and combustible liquids, those with flash points between 37.8°C and 93°C (200°F) thus requiring heat above room temperature to ignite. Petroleum-based and petrochemical materials such as oils, greases, paints, lacquers, cutting and hydraulic oils, solvents, and many gases fall in this class. Water will often not extinguish Class B fires and can often just spread the burning material. These fires are extinguished by blocking the available oxygen from the burning fuel and preventing further release of their vapors. Foams and powders are common extinguishing materials.
- Class C: These occur with energized power lines or electrical equipment and are fueled with materials that otherwise would generally be in Class A or B. Extinguishing agents that are non-electrically conductive, such as carbon dioxide or powders must be used. As the fuels in Class C fires are basically the same as Class A or B, once the electrical power is de-energized, Class A or B extinguishing agents may then be used — but, again, only upon de-energization. Water-based extinguishers used when there is any electricity present would of course be highly dangerous. Multi-class A-B-C dry chemical extinguishers are popular for this reason. Built-in extinguishers in industrial operations and data centers may use argon, nitrogen and/or carbon dioxide as inert gases to extinguish such fires.
- Class D: These are fires of combustible metals, such as magnesium, sodium, and potassium, as well as lithium, zirconium, and titanium. Because of extremely high flame temperatures, water can break down into hydrogen and oxygen, enhancing burning or exploding. Dry powder extinguishers based on sodium chloride, sodium carbonate, graphite, copper powder, or other materials are used. Dry sand free of combustible materials can also be used to smother a metal fire and block oxygen from reaching the burning surface.
- Class K: This category covers cooking oils, greases, and fats, a large risk in commercial food and cooking operations. So-called wet chemical extinguishers, typically an alkaline like potassium carbonate to react with the fatty acids, not only stop the flames and reduce the temperature of the fuel, but react via saponification to form a soap that seals the surface and blocks the vapors. These extinguishers can also be used on Class A and flammable liquid Class B fires.
Please note that in Europe and Asia, while flammable liquid fires are categorized as Class B like in the US, they use the term Class C for flammable gases. Asia uses the term Class E for electrical fires, whereas Europe does not have similar nomenclature in this classification system for them. Also, in Europe and Asia cooking material fires are called Class F vs. the US’ Class K. As always, while physics is universal, confirm the tools and standards most applicable to your situation.
Storage, maintenance, and inspection of extinguishers
As life- and enterprise-critical equipment, fire extinguishers should be treated and managed carefully and properly. This must include:
- Visibly and protectively storing and mounting them in assigned locations, in clear site and reach of the workforce.
- Frequent inspection, such as monthly or bi-weekly, for pressure level, and nozzle, seal, and pin, and overall body condition.
Records of these inspections and any maintenance should be reviewed by management and kept on file through the rated life of the extinguisher, with replacement extinguishers procured and installed when the old ones are out of date.
Emergency Action Plans (EAPs)
According to the United States Department of Labor’s Occupational Safety & Health Administration (OSHA), Evacuation Plans and Procedures eTool site, “An emergency action plan (EAP) is a written document required by particular OSHA standards. [29 CFR 1910.38(a)] The purpose of an EAP is to facilitate and organize employer and employee actions during workplace emergencies”.
This Standard Number 1910.38 covering EAPs states “ An emergency action plan must be in writing, kept in the workplace, and available to employees for review.”
Further, very valuable points to follow as laid out in this standard, are:
1910.38(c) Minimum elements of an emergency action plan. An emergency action plan must include at a minimum:
1910.38(c)(1) Procedures for reporting a fire or other emergency;
1910.38(c)(2) Procedures for emergency evacuation, including type of evacuation and exit route assignments;
1910.38(c)(3) Procedures to be followed by employees who remain to operate critical plant operations before they evacuate;
1910.38(c)(4) Procedures to account for all employees after evacuation;
1910.38(c)(5) Procedures to be followed by employees performing rescue or medical duties; and
1910.38(c)(6) The name or job title of every employee who may be contacted by employees who need more information about the plan or an explanation of their duties under the plan.
1910.38(d) Employee alarm system. An employer must have and maintain an employee alarm system. The employee alarm system must use a distinctive signal for each purpose and comply with the requirements in § 1910.165.
1910.38(e) Training. An employer must designate and train employees to assist in a safe and orderly evacuation of other employees.
1910.38(f) Review of emergency action plan. An employer must review the emergency action plan with each employee covered by the plan:
1910.38(f)(1) When the plan is developed or the employee is assigned initially to a job;
1910.38(f)(2) When the employee’s responsibilities under the plan change; and
1910.38(f)(3) When the plan is changed.
More on OSHA’s Evacuation Plans and Procedures can be found at https://www.osha.gov/SLTC/etools/evacuation/index.html and https://www.osha.gov/SLTC/etools/evacuation/eap.html.
More from the US Occupational Safety & Health Administration on fire hazards and safety may be found at:
Another good resource for learning and training on fire is the US National Fire Protection Association’s News & Research site.
Other information on fire hazards and flammable or combustible materials may be found at:
More information on fire extinguisher basics can be found at:
A cautionary list of major causes of industrial fires and explosions is given here by Nilfisk Inc.’s Industrial Vacuum Division,
Some information on the prevention of explosions can be found here:
From the United States’ National Institute for Occupational Safety and Health (NIOSH):