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Understanding Material Safety Data Sheets (MSDS)

The Material Safety Data Sheet or MSDS is the backup to the label. The label alerts you with a brief profile of a hazardous product; the MSDS contains detailed information about the material. It provides information on the hazardous ingredients, properties and potential health risks of exposure; it explains how to use and store the product safely and what to do in an emergency. It is not only a source of detailed information about particular hazardous materials, but provides data on which effective workplace controls for the material may be based.

The format or design of an MSDS is not specified by law, but it must provide nine separate categories of information. The nine categories are listed and explained below.

                                                                                                 1. PRODUCT IDENTIFICATION

                                                                                                 2. HAZARDOUS INGREDIENTS

                                                                                                 3. PHYSICAL PROPERTIES

                                                                                                 4. FIRE AND EXPLOSION HAZARDS

                                                                                                 5. REACTIVITY DATA

                                                                                                 6. TOXICOLOGICAL DATA

                                                                                                 7. HANDLING PROCEDURES

                                                                                                 8. FIRST AID MEASURES

                                                                                                 9. MSDS PREPARATION INFORMATION




Most MSDS's begin by telling you who made or imported the product, i.e., where the product came from. Most important, this section provides a telephone number to call in case of an emergency - a spill, a fire, an over exposed fellow worker, etc. - - and more information is needed from the manufacturer than is supplied on the MSDS. Also names the product by the same name used on the label, may give the product's chemical name, or list any other name by which the product is known.


This section lists all the hazardous ingredients found in a product (unless an ingredient is a trade secret). The concentration of each ingredient is also listed. Concentration means the weight of the ingredient as a percentage of the weight of the product. The % Concentration may be expressed as a ratio of:

  • Weight to weight
  • Weight to volume, or
  • Volume to volume

    of the total mixture.

    The Chemical Abstracts Service (CAS) number must be given for each ingredient. You may also see PIN number (Product Identification Number) printed on this section of the MSDS. The PIN number is the code number specified for a product in Schedule II of the Transportation of Dangerous Goods Regulations. Both C.A.S. and PIN numbers may be used to confirm the identity of an ingredient or product or to obtain additional information.

    LD50 / LC50

    This section also tells you something about how hazardous each ingredient is by listing its LD50 or LC50.

    The LD50 is the amount of the ingredient that will kill half a test population of animals when that amount is given to them by a certain method (e.g., the material is applied to their skin or fed to them). For example, you might see "Rat, Oral, LD50: 200 mg/kg." That means that half of a test population of rats was killed when they swallowed a dose of 200 mg. of the ingredient for every 1 kg. of body weight. The lower the LD50, the greater the hazard because not as much of the ingredient is needed to kill the test animals.

    The LC50 works in the same way, except that is value refers to the concentration of the ingredient in air (expressed as ppm - - parts per million - - or mg/m3). When breathed in by a group of test animals over a certain period of time, this concentration will kill half of them. Again, the lower the LC50, the more dangerous the ingredient is. Where known, the MSDS must give you the LD50 or LC50 for the entire mixture instead of each of its ingredients. This way you get an idea of how hazardous the mixture is as a whole.


    This section describes the properties of the substance, i.e., it will tell you (when the information is available) how the product will act in certain situations. Some parts of this information are more highly technical than others. Overall, they tell us:

  • Whether the material is a gas, a solid or a liquid
  • What it looks like and smells like when in use
  • How likely it is to evaporate (materials which evaporate easily are usually more dangerous);
  • Whether its gases rise or sink (important for air monitoring and ventilation);
  • How it can enter the body and what effects it may have.


    The physical state of the product (gas, solid or liquid) gives an indication of how the substance may enter the body. Gases usually enter by inhalation, liquids by skin contact and solids by ingestion or contact.

    Where the characteristics described in the MSDS do not correspond to the properties observed in the product itself, the workplace either has the wrong MSDS for the product, or the material may have decomposed during shipment or storage. Further investigation is required.


    This is the level in parts per million at which most people will be able to smell the product. Indicates the lowest airborne concentration of the material that can be detected by the sense of smell. While this may be a useful warning, it must be remembered that some substances are hazardous at concentrations well below this level. Also, the sense of smell differs from one individual to another, and some materials have the effect of desensitizing the sense of smell. If you can smell the product, it means there's a problem brewing and you and your fellow employees have to get help.


    This is the density (weight) of the product compared to water. It reveals whether the material is likely to float or sink in water, and is useful in the planning of clean up procedures and controls.

    If the value is greater the 1.0, then the product will sink in water; if less, it will float. Most flammable substances have specific gravity less than 1.0. This is important information when cleaning up after a fire - - the substance will be floating on top of the water and used to extinguish it. (if water was used)


    Similarly, the vapor density is the density (weight) of a vapor compared to air. Materials with a vapor density of less than 1 (representing the density of air, e.g., helium and methane) are lighter than air and tend to rise when released. Materials with a vapor density higher than 1 tend to sink to the floor upon release (e.g., chlorine and carbon dioxide). That means the vapor may flow to a source of ignition and become a fire or health hazard. Vapor density may be useful in the design of controls such as local exhaust ventilation.


    Vapor pressure is an indicator of the product's ability to form vapors. Products with a high vapor pressure can be extremely hazardous, particularly in confined spaces and unventilated areas. This value, along with the evaporation rate - - the speed at which a liquid or solid turns into a vapor - - tells you how quickly a liquid becomes a vapor, thus exposing you to a potential inhalation danger. Evaporation rates are stated as "slow", "medium", or "fast". Generally, the higher the evaporation rate, the more hazardous the product.


    These properties help determine if the material will change its physical state at normal process temperature or room temperature. They may influence the design of process or storage facilities.


    The pH tells you if the product is a strong acid or alkali. A neutral substance has a pH of 7.0. The strongest acids have a pH of 1.0 to 3.0 and are corrosive to your skin. Strong alkalis have a pH near 14.0 and will also damage skin. Your skin or eyes must be flushed with a lot of water for 15 - 20 minutes if you come into contact with these substances.


    Percentage volatile is the percentage of a product that will evaporate at 20 degrees Celsius - - or other stated temperature. For example, butane, gasoline and paint thinner are 100 percent volatile. Over a period of time, they will all evaporate completely. A volatile product requires specific ventilation and storage controls. Generally, the more volatile a substance is, the more likely it is to present a fire or explosion hazard.


    This number compares the amount of a material that can be dissolved in oil with the amount that can be dissolved in water. Materials with a value of more than 1 are more soluble in water than in oil. This means that the moist membranes of the eyes, nose and throat may absorb these materials from the workplace air. Materials with a value of less than 1 show a better solubility in oils and greases than in water and may, therefore, are able to pass through the skin. This information may help in selecting the right kind of personal protective equipment.


    This section, along with the information on the physical properties, gives you a good indication of the potential fire hazards posed by the material. Describes the likelihood of the material burning or exploding under different circumstances such as: exposure to various temperatures, effects of static electricity, sharp impacts, and so on.

    You will learn here in what situations the material will catch on fire and the type of fire extinguisher you should use to put it out (e.g., water spray, dry chemical or carbon dioxide).


    This section will also tell you the product's flash point - - the lowest temperature at which the vapors above the liquid will ignite in air when exposed to flame. The lower the flash point, the more a product poses a fire hazard because it means vapors will ignite at a low temperature.


    This is the lowest temperature at which a material will automatically catch on fire without a source of ignition. If the auto-ignition temperature is just above room temperature, for example, the material is obviously a real fire hazard.


    These sections tell you that a vapor at a concentration between these limits will catch fire or explode when exposed to flame, spark or other source of ignition. Concentrations below the LFL and LEL are too weak and concentrations above the UFL or UEL are too rich to catch fire and explode.


    This tells you what hazardous products are released when a substance burns. The explosion data will tell you if the product will explode when hit forcefully by another object or dropped (mechanical impact) or when shocked by static electricity (static discharge).


    Some substances are unstable; that is, they react when heated or when they come into contact with another product. As a result, they may cause pressure build-up or increases in temperature, or they may release toxic or corrosive products. This section will tell you when the product is unstable and the name of any materials with which the product reacts.


    This is the tendency of a material to maintain stable and predictable properties. Conditions such as heat, burning, sunlight, and the age of the chemical can cause unstable chemicals to break down into chemicals with different hazardous characteristics. The new chemicals may be even more hazardous than the original. This section states whether the material is stable or unstable.


    The material may be incompatible with other products. If it is, this section will say so and provide the names of the products. It will be important to devise storage systems where incompatible products are kept away from this material.


    This space is used to describe specific conditions under which the material may react (e.g., extremely low or high temperature or pressure).


    Reactive materials may release other substances due to heating, aging, or oxidation. These products of decomposition must be named in this space so that their hazards can be identified, controlled in the workplace and included in emergency plans. You don't want to store incompatible materials near each other or put a material that reacts with plastic in a plastic container. It is also important when choosing personal protective equipment; rubber gloves are of no use if a product reacts to rubber.


    This section of the MSDS explains the health effects which may result from overexposure to the subject material. It will also tell you if effects are immediately dangerous (acute) or if the effects are a result of repeated exposures over a long period of time (chronic).


    This section tells you how the chemicals enter your body - - through the skin, if breathed in (inhaled), swallowed (orally/ingested) or through eye contact. With this knowledge, effective controls against exposure may be implemented, and potentially harmful health effects understood.


    Information in this space describes the health effects experienced immediately or within 24 hours of exposure. For example, a strong does of carbon monoxide may cause dizziness, coma or even death.


    Describes the health effects resulting from repeated exposure to the material over long periods. For example, exposure to regular low doses of carbon monoxide over many years may initiate or aggravate heart problems.


    The exposure limit is the Time-Weighted Average Exposure Value (TWAEV), the Short-Term Exposure Limit Value (STELV) or he Ceiling Exposure Value (CEV) of the subject material. Exposure limits used in conjunction with air monitoring will indicate whether controls against the material are working effectively.


    This entry indicates the strength and capacity of the material to cause irritation to the eyes, nose throat or skin, which provides important data for the selection of protective equipment.


    This space should indicate whether or not the material has a synergistic relationship with any other product or agent and, if so, identifying the product or agent. Synergy is the tern used to describe effects created by two or more materials where the cumulative effect is greater than the sum of their separate effects.


    This section state whether the material has or is suspected of having any cancerous or reproductive effects in humans or laboratory animals.


    This is a very important section because, above all others, this one tells you how you can protect yourself from potential harm.

    It details specific personal protective equipment (protective goggles, respirators, gloves, boots, etc.) that are needed to work safely with the product. It also tells you how to safely handle, store, ship and dispose of the product and what to do in case of a leak or spill.


    This section tells you what to do if you or a fellow employee is hurt because of contact with the substance by inhaling it, swallowing it or splashing it on the skin or in the eyes.


    Who - - or what group or department - - prepared the MSDS, the telephone number at which a member of that group may be reached for further information and the date of preparation are all important to ensure the accuracy and currency of the MSDS. The MSDS will remain valid for three years from the date shown in this section - - unless new information becomes available before then.


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