The Lowdown on Material Safety Data Sheets

Diane Kelly

August 2008

When the Occupational Safety and Health Administration created the Hazard Communication standard in 1986, a major component was the Material Safety Data Sheet. Manufacturers were required to provide MSDS, and general industry employers maintained them in the workplace. A construction industry version of the standard came along shortly after; it required contractors to maintain the MSDSs on job sites.

An MSDS is designed to provide workers and emergency responders with safe procedures for handling or working with a particular substance. An MSDS contains a huge amount of information that can be very challenging for a chemist, so it is even more intimidating to someone on the average job site. However, by reviewing an MSDS for a common chemical hazard, it will help make it easier to understand its content and value for all chemicals.

Before beginning it is important to know that no one format exists for MSDSs. Although OSHA provides a recommended format, the OSHA 174, other formats are accepted. In fact, in recent years OHSA has recommended using the American National Standards Institute’s version.

The OSHA 174 form requires a minimum amount of information. It contains seven sections beginning with the manufacturer’s information and ending with Control Measures. The ANSI MSDS contains 16 sections beginning again with manufacturer information, but ending with "Other Information.” Regardless of format, the key is to focus on the important content, understand it and be able to use it.

Know Your Info
Knowing how to read an MSDS for gasoline, for example, could help avoid dangerous situations. Having the manufacturer’s emergency contact information, the chemical’s health effects, first aid procedures, storage and disposal information, and even the substances physical data, such as melting point and boiling point, could save lives. Much of this information will be straightforward on the MSDSs. Little explanation is needed in reviewing the first aid procedure section: "Do not induce vomiting if ingested,” "Flush eyes for 15 minutes if exposed” and the like. Other technical information may seem more difficult, but can be just as valuable.

The section on the chemical’s identity can be very revealing. Common substances, including gasoline, can be made up of other ingredients. Benzene, a cancer causing agent, can be found in gasoline.

As you review the identity, you will see the percentage found in the substance and the exposure limits to the chemical. Exposure limits are usually identified as Threshold Limit Value or Permissible Exposure Limit. These are time-weighted averages based on 8-hour work shifts. Although it takes monitoring of the workplace to determine exposure level, the numbers provide an indication of the relative danger. The lower the number, the more easily you can be exposed to dangerous levels. Measurements listed in Short-Term Exposure Limit reveal that even short periods of exposure can be dangerous.

What the Numbers Mean
Looking into the Physical and Chemical Characteristics section helps you identify the presence of the chemical and predict pending danger. The appearance and odor of gasoline are described as "a translucent, straw-colored or light yellow liquid” and "a strong, characteristic aromatic hydrocarbon odor.”

Gasoline’s vapor density is 3 to 4. This is its relative weight as compared to air. Air is 1. Therefore, gasoline vapors are heavier than air, which means gasoline vapors may sink or be found at lower levels, such as down elevator shafts or in ditches.

Gasoline’s specific gravity or relative weight compared to water and solubility describe how it interacts with water. Gasoline has a specific gravity of less than 1. This means it is lighter than water, and it will float on water.

Gasoline’s solubility is almost zero. That means it does not dissolve in water; simply put, it will not mix with water. That’s why the use of water on a gasoline fire is of little value.

Know the Limits
The section on a substance’s Fire and Explosion Data or Firefighting Measures usually provides easily understood information. For gasoline, it describes the firefighting needs as "extinguisher suitable for Class B fires, dry chemical, CO2, water spray, fire fighting foam or Halon.” It also provides more technical data, such as flashpoint and explosive limits.

Flashpoint is the lowest temperature at which the chemical will ignite in air. Gasoline’s flashpoint is –45º F. This makes it nearly impossible to start gasoline engines in extremely cold climates; not enough vapor is given off to ignite. It also reveals that even at low temperatures, enough vapor can be in the air for a fire.

The explosive limit of gasoline (lower limit 1.4 percent) tells us that only small amounts are needed in the air for a fire or explosion. (That’s another reason why you should never light up your stogie while you’re filling up your convertible at the gas station.) When dealing with a chemical’s flammability hazard, consider both the straightforward information as well as the technical data.

More Possible Mixups
Another important section that generally contains easily understood information as well as technical data is the Reactivity Section. On the more straightforward side, it identifies other chemicals that will react negatively with the substance. Mixing gasoline with oxidizers or substances that give off oxygen readily can cause explosive mixtures.

The technical complexity comes with two words: polymerization and decomposition. Polymerization simply means that a substance can transform itself. Its molecules link forming chains or polymers. Gasoline will not form hazardous polymers.

Many chemicals will decompose by themselves or decompose through a reaction like a fire. Gasoline will decompose through fire or when mixed with nitric acid. This creates other hazardous chemicals.

Reading MSDSs will better prepare you to work safely. The basic information and technical data can prove useful. Take time with the MSDSs. Consider what the technical data reveal about how the chemical will be present or used in the workplace, and how it will act.

If an emergency occurs, know where the MSDSs are located and where to find the necessary emergency information on the MSDS.