How to Read an MSDS

When reading an MSDS, the Lawrence Berkeley National Laboratory’s Chemical Hygiene and Safety Plan recommends keeping the following in mind: At times, the MSDS may outline only the minimum precautions for safe handling of the chemical in the sections on fire and explosion hazards, spill or leak procedures,  special protection information, and special precautions.

When no mention of a particular health effect is made in the MSDS, it should not be assumed that the substance is hazard-free. Test results may not have been available when the MSDS was prepared; testing of the substance is not required to create an MSDS. You should expect a completed MSDS with no blank spaces. If an MSDS with blank spaces is received, the supplier should be questioned. If certain data are not available, the MSDS should state so in the space provided.

In many cases, the emergency first aid procedures and handling precautions are written to deal with a worst-case scenario, such as extensive exposure. Knowing this fact, you may believe, for a seemingly minor incident, that immediate medical attention is not required even though it is called for by the MSDS. Please keep in mind that in the absence of an informed opinion by a designated health professional, a prudent response is the best policy.

It is important to check the date when the MSDS was prepared. Out-of-date MSDS(s) may not be reliable.

Product Identity

The MSDS should include the name of the product as it appears on the label. Keep in mind a product may be a mixture of two or more chemicals. Manufacturer’s name, address, and phone number should be included. If the data comes from a source other than the manufacturer, the actual source must be indicated. The date of preparation or revision must be indicated.

Twenty-four hour number(s) should be provided by manufacturers so that emergency information can be obtained when necessary. Look for the general class of compounds to which the hazardous substance or mixture belongs (e.g., ethers, acids, ketones, solvents). This term does not give you the exact content of the product. If the product is a mixture, all hazardous ingredients must be listed.

Threshold Limit Value (TLV) and Permissible Exposure Limit (PEL) are included in this section, or under Health Hazards. Note that the higher the number for a TLV or PEL, the less hazardous the substance.

The percent column is intended to show the approximate percentage by weight or volume of each hazardous ingredient compared to the total weight or volume of the product. Normally, percentages will be listed to the nearest 5 percent. When the substance constitutes less than 5 percent of the product, this is indicated.

This section contains very important data to help predict the behavior of the material in experimental situations. The information provided is for the material as a whole, rather than for each hazardous ingredient. Vapor pressure, vapor density, percent volatiles, and evaporation rate all basically tell you the same thing: whether breathing the vapors will be a problem, thus indicating the need for proper ventilation.

Boiling point: The temperature at which a liquid changes to a vapor at a given pressure; usually in degrees Fahrenheit at the sea-level pressure of 760 millimeters of mercury (mm of Hg). For mixtures, the initial boiling point or the boiling range may be given. A low boiling point may be a special fire hazard.

Vapor pressure: Refers to the pressure exerted by a saturated vapor above its own liquid, usually stated in mm of Hg at 25ºC (77º). The lower the boiling point, the higher the vapor pressure. A high vapor pressure indicates easy evaporation. Vapor density: Tells whether the material is heavier or lighter than air. This is useful information to indicate a confined space hazard. If heavier than air, the material will concentrate in low places, such as floors, elevator shafts, sewers or the bottom of tanks.

Percentage volatility by volume: How much of the material evaporates at room temperature. A substance that is 100 percent volatile will evaporate completely, leaving no residues.

Evaporation rate: The rate at which the material will evaporate when compared to the rate of evaporation of a known material, usually butyl acetate. If another material is used for comparison, it should be indicated. If the number is greater than 1, the product evaporates more easily than the comparison material.

Solubility in water: The percentage of a material (by weight) that will dissolve in distilled water, at room temperature.

Specific gravity: The ratio of the weight of a volume of material to the weight of an equal volume of water. For insoluble materials, a specific gravity of less than one means the material is lighter than water and will float. Greater than one means that it sinks in water.

Melting point: The temperature at which a solid becomes a liquid under normal room conditions.

Appearance and odor: A brief description of the material at normal room temperature and atmospheric conditions. Do not rely on odor to alert you to a dangerous exposure. Some substances can reach hazardous levels and have no noticeable odor.

Fire and Explosion Hazard Data

This section should clearly indicate whether the material is flammable. If it is flammable, make sure there are no ignition sources nearby and that you have the correct fire extinguisher on hand. If you work with solvents, peroxides, explosives, metal dusts or other unstable substances, this section is very important.

Flash point: The lowest temperature at which the material gives off enough vapor to ignite; this will help determine storage and handling procedures. The method used to obtain this information should be stated. Flammable or explosive limits: The range over which a flammable vapor, when mixed with the proper proportions of air, will flash or explode if ignited. The range is designated by lower explosive limit (LEL) and upper explosive limit (UEL), and is expressed in percentage of volume of vapor in the air.

Extinguishing media: Indicates what type of fire extinguisher to use, such as water, fog, foam, alcohol foam, carbon dioxide or dry chemical.

Special firefighting procedures: Special handling procedures, personal protective equipment, and unsuitable firefighting substances should be listed. For example, water should not be used on fires involving reactive metals. General firefighting methods are not described.

Unusual fire and explosive hazards: Hazards that might occur as a result of overheating or burning of the material, including any chemical reactions or change in chemical form or composition.

This section indicates how unstable the substance is and lists conditions to avoid preventing dangerous reactions. This information will help you handle and store the material properly.

Stability: The checked box will indicate whether the material is stable or unstable and under what conditions instability occurs.

Incompatibility: Lists materials and conditions to avoid. Such conditions may include extreme temperatures, jarring, or inappropriate storage. This is important to determining what other chemicals the material can be stored or used with.

Hazardous decomposition products: A list of the hazardous materials that may be produced if the material is exposed to burning, oxidation, heating, or certain chemical reactions. The product shelf life should be included, when applicable.

Hazardous polymerization: Polymerization is a chemical reaction in which two or more molecules of a substance combine to form repeating structural units of the original molecule. A hazardous polymerization causes an uncontrolled release of energy (heat). If this reaction can occur, it must be indicated.

This section lists routes of entry (inhalation, skin absorption, ingestion), and gives signs and symptoms of overexposure, such as skin rash, tremors or dizziness. Short-term (acute) and long-term (chronic) health hazards, such as the ability to cause cancer (carcinogenicity), birth defects (teratogenicity), or “target organ” damage, should be listed.

Some products cause both types of effects. Unfortunately, this important section often lacks adequate information, especially on the health effects of long-term exposure. Instructions for first aid and emergency procedures for victims of acute inhalation, ingestion, or skin or eye contact must be included. Medical conditions that can be aggravated by exposure must also be detailed.

This information will help you prepare for emergencies by having the proper materials and equipment on hand. This section lists methods, special equipment, and precautions necessary to control and clean up spills, leaks, and other releases. For example, if respirators are required to clean up a spill, that fact should be shown.

Acceptable waste-disposal methods, as well as prohibited methods, are described. The user will also be alerted to any potential environmental danger to the general population, crops, water supplies, etc. Instructions for safe handling and storage, such as the warning not to store acids and bases together, may be given. Any additional special precautions not addressed elsewhere in the MSDS should also be listed here. These may include instructions for storage life or transportation, such as special packaging or temperature control.