Flammable and Combustible Materials

Without the proper controls in place, fires are more likely in your facility and will be more difficult to contain.

• By Craig Schroll
• Jul 01, 2004

EFFECTIVE management of flammable and combustible materials is a critical fire prevention and protection issue. The essence of fire prevention is keeping potential fuel away from ignition sources. Although we attempt to control both sides of this issue, I will focus on the fuels in this article and, more broadly, on flammable and combustible materials of all types. My previous article on the subject in this publication ("Flammable Liquid Safety," March 2002, page 50) focused on flammable and combustible liquids.

Numerous regulations, codes, and standards have an impact on this topic area. A few sources for information on requirements are the OSHA regulations, National Fire Protection Association (NFPA) standards, and various state and local fire codes. For gases, the Compressed Gas Association is one of the best sources of information.

Flammable and combustible materials are present in all of our environments. Workplaces, public venues, and our homes are filled with flammable and combustible materials. Without the proper controls in place for these items, it is more likely that fires may occur in your facility--and any fires that do occur will develop more quickly and be more difficult to contain and control.

The physical state of the fuel should be considered. Only vapors and gases burn. The nearer to this state the fuel is naturally, the easier it is to ignite. Flammables are generally in the gas, vapor, or liquid state naturally and therefore present extra challenges.

Handling Flammable Gases
Flammable gases are typically divided into two primary categories: fuel gases and industrial gases. Fuel gases include natural gas (methane) and liquified petroleum (LP) gas (propane). As the name implies, these gases are used as fuels for building heat, industrial processes, and motor vehicles. Industrial gases include all flammable gases not usually used as fuels: for example, acetylene, MAPP gas, and hydrogen.

Flammable gases are distributed to and within our facilities either in fixed piping or cylinders. Proper design and maintenance of piping systems and gas-consuming equipment is necessary.

Cylinder handling and storage is another important issue. Segregating flammable gas cylinders from other gases, particularly oxygen and other oxidizers, is an essential minimum element. Cylinders always must be secured while in storage and protected from other physical damage. Some cylinders are used as portable supplies for gas, such as acetylene used with a portable cutting torch. Other cylinders may be used to supply fixed installatons, such as a hydrogen cylinder suppling gas to laboratory equipment.

If you use gas as a motor fuel for industrial trucks, motor fuel cylinders and their refilling are issues you must handle properly. Cylinder refilling areas should be well away from the building, at least 50 feet, but farther is better. Operators must be trained in the proper procedures for cylinder removal from the vehicle, refilling, and replacement on the vehicle. There is a tendency based on many repetitions of this task for truck operators to become too casual about the potential for a fire during the refilling process; another significant opportunity for problems is when LP gas is delivered to refill your site storage cylinder. Someone from your facility should always observe this process.

Controlling fuels that are part of a process is often primarily accomplished through proper operation of the system and an effective preventive maintenance program. In these two areas are the most frequent opportunities for fuels to escape a process.

Operations may be improved with system design and operator training. System designs can contribute to safety in a number of specific ways. Automatic control of flammable materials is one method. For example, an excess flow valve will reduce the flow of an escaping gas by detecting an absence of back pressure. This way, if a pipe breaks, the flow through the break will be substantially reduced.

Automatic system controls are another example. The ventilation system of a process using flammable liquids may be equipped with gas detection equipment that can sound an alarm notifying the operator or can be set to shut down the process automatically.

Operator Training & Maintenance
System design also should incorporate human factors issues. For example, an indicator on a control console that is difficult to interpret makes the task of the operator unnecessarily hard. Misinterpreting the indicator could lead the operator to take the wrong action and result in a greater problem.

Operator training needs to cover both normal and emergency procedures. Operators of processes that use flammable gases or liquids must be intimately familiar with the process, controls, and indicating systems. Their training should be as realistic as possible and cover all identified potential problems they may encounter with the process. For complex processes,written procedures should be developed to assist operators during abnormal conditions and emergencies.

To the extent possible, maintenance of these systems should be accomplished frequently enough to identify issues before they become releases. Use an established schedule of preventive maintenance and system testing, and include ancillary components such as ventilation systems in routine maintenance activities.

Combustible Materials
Combustible materials in our facilities can contribute to the start and growth of a fire. The amount, type, and form of combustibles make a significant difference in how much of a challenge they present. The more finely divided the combustible material, the easier it is to ignite. At the extreme end, very finely divided materials suspended in air may explode under some circumstances. Most people have seen news reports covering grain storage facility explosions; many other dusts and finely divided particles also present this hazard.

Even a simple issue such as housekeeping is critical to fire prevention. This often looks like a boring, unimportant item, but it is not. How well or poorly we control the general combustibles that tend to accumulate in our facilities can make a big difference during a fire. Pallets are an excellent example; how you manage your pallets can have a large impact on the amount of combustible materials in your facility. Large stacks of pallets in the main area of your facility invite a large, rapidly developing fire.

Housekeeping includes maintaining clear aisles throughout your facilities. Aisles serve a few important roles. First, they provide a separation of processes and stored materials that minimizes the opportunity for a fire in one area to move quickly to another. Aisles also provide access for fire control efforts.

Fuel load refers to the potential heat release available from the materials in an area. It is primarily a function of the total quantity of material and the heat release rate of those materials. In a warehouse that stores metal parts in metal bins on metal racks, for example, the anticipated heat release from a fire would be quite low. If the warehouse contained plastic parts in plastic bins, the heat released during a fire would be very high. Quantity can vary based upon the storage arrangement. If a warehouse stores material on pallets stacked only two high, the available fuel during a fire would be half as great as if the pallets were stacked four high. Arrangement of the fuel may also affect the performance of fire protection systems and manual fire control efforts.

Combustible metals are a specialized area. For operations that do use these materials, special precautions are essential, particularly if the metals are being processed in some way. Machining operations that generate fine particles or shavings in the presence of heat are especially prone to fire. Some combustible metals also may be reactive, which magnifies the risks.

Impact of Changing Processes
Without turning this into an article on design of fire protection systems, we do need to consider an area's fuel load when designing fire protection systems. Automatic sprinkler systems, for example, are designed to achieve a certain minimum flow of water. This flow is expressed as gallons per minute per square foot (gpm/ft2). This amount of water flow is based upon the anticipated fire in the area being protected, which is determined from the combustibles that are expected to be in the area.

An understanding of the intended use of a facility is necessary to design an appropriate system. This initial design is not usually a problem, but difficulties often occur when the use of an area changes. If an area originally designed for light assembly of metal parts is changed to injection molding of plastic parts, chances are good the original sprinkler system is not up to the new challenge.

Controlling flammable and combustible materials is often not a priority of our safety processes. While it is usually not a difficult task, it is frequently overlooked. Handling a few basic elements effectively can go a long way toward improving your fire prevention and protection.

This article originally appeared in the July 2004 issue of Occupational Health & Safety.