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Chemical Hazard Categories

Several terms are used to describe chemical hazards that can harm both people and property. A "flammable" material is an example. When defining these terms, we reference a chemical's "flash point."

Flash point

Flash point is the lowest temperature at which a liquid will give off enough flammable vapors near its surface to cause the material to ignite when an ignition source is introduced. "Flammable" categories are determined by a chemical's flash point and boiling point. Boiling point is the temperature at which a liquid changes from a liquid state to a gas state.

Some chemicals have flash points that are lower than room temperature. These chemicals can give off vapors in sufficient concentrations to form an ignitable mixture. Fire guidelines are determined by a chemical's flash point.

A Flammable liquid means any liquid having a flashpoint at or below 199.4 degrees Fahrenheit, or 93 degrees Celsius. Flammable materials are divided into four categories:

• Category 1 materials have a flash point below 73 degrees Fahrenheit and a boiling point at or below 95 degrees Fahrenheit.
• Category 2 materials have a flash point below 73 degrees Fahrenheit and a boiling point above 95 degrees Fahrenheit.
• Category 3 materials have a flash point at or above 73 degrees Fahrenheit and a boiling point at or below 140 degrees Fahrenheit.
• Category 4 materials have a flash point above 140 degrees Fahrenheit and a boiling point at or below 199.4 degrees Fahrenheit.

Remember to remove all sources of ignition when using flammable chemicals. Open flames, electrical equipment, static electricity, matches, and hot surfaces are all sources of ignition.

These are several terms commonly associated with the physical hazards of chemicals, which occur outside the body:

• Pyrophoric substances are chemicals or materials that ignite spontaneously in air at a temperature of 130 degrees Fahrenheit or lower.
• Explosives are chemicals that cause a sudden, almost instantaneous release of energy, pressure, gas, and heat when subjected to sudden pressure, shock, or high temperature. Examples include hydrogen and coal dust.
• Gases under pressure are gases which are contained in a receptacle at a pressure of 200 kPa (29 psi) or greater.
• An oxidizer is a substance, not necessarily containing oxygen, which causes or enhances the combustion of a fuel or propellant.
• Unstable or reactive, refer to the tendency of a substance to undergo chemical reaction with the release of energy during normal handling or storage. If so labeled, safety precautions should include segregation and prohibition of mixing without personal protection and precautions.

Detecting hazardous materials

Your senses can often warn you of the presence of hazardous materials in your work area. For instance, natural gas has an odorant additive meant to give it a distinctive smell. However, your senses alone aren't adequate to alert you to the presence of chemicals. Sampling devices and detection instruments may be needed to accurately identify hazardous chemicals. Your employer will use several methods to detect hazardous chemicals in the workplace.

If used improperly, chemicals can create sickness and injury. You should become familiar with these terms related to chemical health hazards:

• A carcinogen is a substance or agent capable of causing or producing cancer—for example, asbestos, benzene, and ionizing radiation.
• A mutagen is a substance or agent that causes an increase in the rate of change in genes that can be passed along as the cell reproduces sometimes leading to defective cells or cancer.
• A corrosive is a material that causes visible destruction or irreversible damage to human skin tissue at the site of contact, or has a high corrosion rate on steel. Gloves and goggles should be used when handling highly corrosive chemicals such as sulfuric acid, hydrochloric acid, or potassium hydroxide.
• A teratogen is a substance or agent that can cause damage to a developing fetus. Examples include methyl mercury, lead, carbon tetrachloride, and ionizing radiation.
• A toxin is a poisonous substance that can cause a harmful effect on the human body. The greater the toxicity, the less dose you can tolerate without becoming sick. Examples include lead, mercury, and arsenic.
• An asphyxiant is a substance that deprives the body of oxygen by displacing oxygen in the air. Examples include carbon dioxide, nitrogen, and argon. It's also a substance that chemically binds with blood cells preventing the absorption of oxygen. Carbon monoxide is an example.
• An irritant is a substance that can cause an irritating effect when it contacts the skin, eyes, nose, or respiratory system. Examples include ammonia and chlorine.
• A sensitizer is a substance which on first exposure causes little or no reaction, but on repeated exposure may cause an allergic reaction of the skin or the respiratory system. Formaldehyde is an example.
• Target organ effects are chemical effects that interfere with the operation of or contribute to the destruction of specific major body organs, such as the liver, kidneys, brain, etc. For example, asbestos harms the lungs.

Some chemicals can affect you immediately after exposure (acute). Other chemicals can accumulate in your body and cause health problems over time (chronic).