In today’s world of chemicals, flammable and combustible liquids pose a grave fire risk that threatens workers safety and the workplace. Because flammable and combustible liquids have become ubiquitous in the workplace and their potential hazard is so high, understanding those liquids is essential in the prevention and control of their hazards.
OSHA 29CFR1910.106 applies to the handling, storage and use of flammable and combustible liquids. The basis of the standard is NFPA publication 30. OSHA, a division of the Department of Labor (DOL), considered NFPA as a primary source for best practices as it relates to flammable and combustible liquids.
The National Fire Protection Association (NFPA) released a report, February 2012, entitled “The total cost of fire in the united states” where they reported that the U.S. spent an estimated $331 billion on fire in 2009. In a previous report NFPA estimated 1,400 fires occurred annually between 2002 and 2005 where flammable liquids were the major contributor for the fire.
In order to understand flammable and combustible liquids, it’s important to understand the terminology used to define them and their potential hazards. It’s also important to understand that the flammable and combustible liquids themselves do not burn. It’s their vapor mixed with air, within a specific range, that burns. Since the flash point determines the liquids ability to generate vapor, flash point became the basis for classification and identification of flammable and combustible liquids.
The flash point characterizes the fire hazards of liquids. The lower the flash point the lower the temperature at which the liquid gives off vapor and the more flammable the liquid is. For example, the flash point for gasoline is –45 deg. F, which means that the liquid gives off vapor at room temperature and much lower and therefore it’s highly flammable.
Flash point is defined as the minimum temperature at which a liquid gives off sufficient vapor that can form an ignitable mixture with air. At its flash point temperature, the liquid vapor flashes when lit in an open container. Flash point shouldn’t be mixed up with fire point, which is normally 5 to 10 degrees higher than the flash point. At its fire point temperature, the liquid vapor sustains fire when lit in an open container.
OSHA defines flammable liquid as any liquid having a flash point below 100 degrees Fahrenheit (deg. F). Flammable liquids are known as Class I liquids and divided into three sub-classes; class IA, class IB and class IC depending on their flash point temperature.
Combustible liquids are defined as any liquid having a flash point at or above 100 deg. F and divided into two classes; Class II and class III. In turn, class III is divided into two sub-classes; class IIIA and class IIIB liquids depending on their flash point temperature.
Too much vapor to air will make the mixture too rich and too little vapor to air will make the mixture too lean to burn. It’s the proper mixture of vapor to air ratio that gives rise to the fire risk. The flammable range is the limit between the minimum concentration and the maximum concentration of flammable vapor in air, in which a flash will occur in the liquid if ignited. Those limits are referred to as the lower and upper flammable limits (LFL or UFL). The vapor mixture below its LFL or above its UFL will not burn.
Because of their high potential for fire hazards, flammable and combustible liquids should be handled, used and stored with great caution. Metal containers and portable tanks used for flammable liquids should be made of proper material and should be properly vented. In most instances, grounding of containers while filling tanks is a must to avoid accidental static charge sparks. Storing of flammable liquids should be done in accordance with the OSHA standard. Suitable fire control devices, hoses of fire extinguishers, should be available at locations where flammable or combustible liquids are stored.
Complying with OSHA 1910.106 is a good way to ensure safety and prevent accidental fires.
