Physical Hazards

By Joe O'Connor | Apr 15, 2004




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A lost requirement of OSHA’s Hazard Communication Standard

When the Occupational Safety and Health Administration (OSHA) issued the Hazard Communication Standard, our industry was overwhelmed. Mountains of paper were assembled to comply. Dangerous physical hazards seemed to take a back seat. This article will revisit those various physical hazards, their danger and general precautions.

A physical hazard defined by OSHA is “a chemical for which there is scientifically valid evidence that it is a combustible liquid, a compressed gas, explosive, flammable, an organic peroxide, an oxidizer, pyrophoric, unstable (reactive) or water-reactive.” Most substances that fit this definition fall into the subcategories of flammable or compressed gas. However, with the almost limitless number of chemicals developed for home and industry, many products fall into other subcategories. For example, hydrogen peroxide, a common household chemical, is an oxidizer. It is important to identify the physical hazards products present and understand them.

Because of our familiarity with fire, the physical hazards of combustible liquids and flammables are easiest to address. With few exceptions, a combustible liquid has a flashpoint at or above 100 F, but below 200 F. Flammables are divided into three categories by physical state (gas, liquid and solid). A flammable gas is one that “at ambient temperature and pressure, forms a flammable mixture with air at a concentration of thirteen percent by volume or less; or a gas that, at ambient temperature and pressure, forms a range of flammable mixtures with air wider than 12 percent by volume, regardless of the lower limit.” Flammable liquids are liquids with a flashpoint below 100 F. A flammable solid is a material that will ignite or cause a fire through friction, absorption of moisture, spontaneous chemical change and/or when ignited burns “vigorously and persistently.” Pyrophoric substances are merely a special subcategory; a pyrophoric substance is one that will ignite spontaneously in air at a temperature of 130 F or below.

There are a few simple rules for safety with flammables. Know the ignition temperature of all substances in the work area. Ignition sources can be a hot light bulb or a static spark. Keep the area free of ignition sources. Use proper ventilation to keep flammables at safe levels.

Compressed gases are gases in a container with a pressure of more than 40 psi at 70 F or over 104 psi at 130 F. Liquids with a vapor pressure over 40 psi at 100 F also fall into this subcategory. Many compressed gases greatly exceed these pressures. Cylinders may contain over 2,500 psi and can become high-energy explosives if ruptured.

When dealing with compressed gases, keep the protective caps on when moving cylinders. Secure cylinders after moving or when transporting in a vehicle. Do not release gas suddenly. Use appropriate regulators. Do not use the entire contents of a cylinder. Ground cylinders that contain flammables or are used with flammable substances.

Compressed air is a compressed gas. Even at low pressure it can cause injury; 12 pounds per square inch of pressure is enough to pop an eyeball from its socket. Air pressure should be kept as low as possible to perform the job adequately and employees forbidden to use air to clean their body or clothing of any dust.

Explosives are chemicals that cause a sudden release of pressure and heat when subjected to sudden shock, pressure or high temperature. An example of this is sodium azide, a substance found in automobile air bags. Six people were injured and one killed from one explosion of the residue on a tank when a worker was grinding the metal duct.

Oxidizers and organic peroxides are similar. Oxidizers initiate or promote combustion in other materials through the release of oxygen or other gases. An organic peroxide in simple terms is a substance with carbon in it that also has an oxygen component that may be released. This combination is deadly. The carbon provides the fuel and the free oxygen promotes fire.

Know what substances on the job will release oxygen. Use only the amount required for a job. Keep them away from other substances. Do not put unused chemicals back in their original bottles. Do not allow peroxides to freeze. Avoid heat and contact with metals. Log the date the chemical was opened.

Unstable (reactive) means a chemical which “will vigorously polymerize, decompose, condense or become self-reactive under conditions of shocks, pressure or temperature.” Know the conditions that cause a chemical to react. Keep incompatible chemicals apart. Certain reactions are caused by catalysts, which are chemicals or conditions that cause or speed up a reaction.

With a basic understanding of these hazards, the key to chemical safety is simple. Every hazardous substance has a Material Safety Data Sheet (MSDS). It must be in the work area and may be the best chemical reference. It will help to classify the hazard, identify any special concerns, and link the substance to the basic precautions. EC

O’CONNOR is with Intec, a safety consulting, training and publishing firm that offers on-site assistance and produces manuals, training videos and software for contractors. Based in Waverly, Pa., he can be reached at 607.624.7159 or [email protected].


About The Author

Joe O'Connor is with Intec, a safety consulting, training and publishing firm that offers on-site assistance and produces manuals, training videos and software for contractors. Based in Waverly, Pa., he can be reached at 607.624.7159 or [email protected].


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