The Solvents Industry Group of the American Chemistry Council (ACC) and its members promote use of adequate precautions at all stages of solvent handling. Statutory and regulatory requirements regarding flammability are important and the group members work to help educate solvent users, distributors, and transporters so they can better understand these requirements. Some hydrocarbon and oxygenated solvents readily evaporate and are highly flammable. These solvents need to be managed carefully to minimize risks of a fire or explosion, whether use occurs in the home or in an industrial setting—particularly during loading and unloading, storing, and when using in bulk. Safe handling information provided by the supplier should be carefully followed.
When solvent vapors are mixed with air they may (like gasoline vapors) form flammable mixtures that will ignite and burn when exposed to a spark or flame.
Solvents can be handled safely if common sense precautions are understood and followed. These precautions are based on the following principles:
- Vapors burn when mixed with air (or other sources of oxygen) in certain proportions.
- Air vapor mixtures burn when a source of ignition is ignited.
- Liquid or vapor can settle in low areas and travel along the surface.
From the above it follows that fire hazard or explosion can be minimized by:
- Controlling vaporization
- Controlling air-vapor concentrations
- Eliminating ignition sources (sparks, flames, static electricity and excessive temperatures)
- Eliminating spills
Flammable Limits and Flash Point
In a solvent/air mixture, the proportion of solvent vapor that makes it flammable is of primary importance. The flammable limits typically range for most products from about 1% to 10% at atmospheric pressure. If there is less than 1% of solvent vapor or more than 10% (depending upon the solvent), the mixture is either too lean or too rich to burn. For a particular solvent, the lowest temperature at which vapor is produced in sufficient concentrations to create a flammable mixture (approximately 1%) under test conditions is its flash point. Flash point is thus a major factor in establishing safety procedures. Closed cup flash point is used by the Department of Labor (DOL) and the Department of Transportation (DOT) in defining the degree of hazard. OSHA defines materials with flash points of less than 100° F as "Flammable."
Anyone using or handling solvents or any other flammable materials should be aware of the hazard of spark-ignited fire and explosion, and all appropriate measures should be taken to eliminate ignition sources, prevent static electric charge build-up, and accumulation of flammable vapors in air. General preventive measures may include the following:
- To prevent static-buildup, for example, bond or ground equipment to provide a conductive electrical path.
- Keeping solvent containers closed in the workplace.
- To dissipate static charge, for example, before transferring liquid by means of a hose and nozzle, attach the grounding wire to the receiving container and maintain contact between nozzle and container during filling.
- Establish procedures to minimize splashing and spraying of solvents being transferred; for example, transferring liquid into a tank.
- Eliminate ignition sources in the workplace.
Handling and preventive measures may be specific to each product. See the MSDS and the manufacturer's directions for specific handling directions for each product.
Ignition may also occur without a spark or flame. If the product is heated well above its flash point, a temperature is reached at which the product will ignite spontaneously, without any external source of ignition, provided sufficient oxygen is present. This is called autogenous ignition and the temperature at which it occurs is the auto-ignition temperature of the product. Users should never exceed the auto ignition temperature of any solvent.
For more information about handling solvents, view: Working with Modern Hydrocarbon and Oxygenated Solvents: A Guide to Flammability and Static Electricity (2011)