MSDS Glossary
- Pathologic
- Pertaining to or caused by disease.
- Pathology
- Scientific study of alterations produced by disease.
- PEL
- Permissible Exposure Limit is an occupational exposure limit established by OSHA's regulatory authority. It may be a time-weighted average (TWA) limit or a maximum concentration exposure limit.
- Percent Volatile
- Percent volatile by volume is the percentage of a liquid or solid (by volume) that will evaporate at a temperature of 70°F. Examples: butane, gasoline, and paint thinner (mineral spirits) are 100 percent volatile; their individual evaporation rates vary, but in time, each will evaporate completely.
- pH
- The symbol relating the hydrogen ion (H+) concentration to that of a given standard solution. A pH of 7 is neutral. Numbers increasing from 7 to 14 indicate greater alkalinity. Numbers decreasing from 7 to 0 indicate greater acidity.
- Physical Hazard
- Used to describe a chemical that is explosive, flammable, an organic peroxide, an oxidizer, pyrophoric, unstable, or water reactive.
- Placenta
- A structure attached to the wall of the uterus to nourish the fetus during pregnancy.
- Polymerization
- A chemical reaction in which one or more small molecules combine to form larger molecules. A hazardous polymerization is such a reaction that takes place at a rate that releases large amounts of energy. If hazardous polymerization can occur with a given material, the MSDS usually will list conditions that could start the reaction and, if the material contains a polymerization inhibitor, the length of time during which the inhibitor will be effective.
- ppb
- Parts per billion. The concentration of a particular chemical in solution. For every one part of the chemical. there are a billion parts of solution. Used to express very low concentrations.
- ppm
- Parts per million. The concentration of a particular chemical in solution. For every one part of the chemical, there are a million parts of solution. Used to express very low concentrations. One inch in sixteen miles is a common example of the magnitude of parts per million.
- Prenatal
- Preceding birth.
- psi
- Pounds per square inch is the pressure a material exerts on the walls of a confining vessel or enclosure. For technical accuracy, pressure must be expressed as psig (pounds per square inch gauge) or psia (pounds per square inch absolute; that is, gauge pressure plus sea level atmospheric pressure, or psig plus approximately 14.7 pounds per square inch). See also mmHg.
- Pulmonary
- Relating to, or associated with, the lungs.
- Pulmonary Edema
- Fluid in the lungs.
- Pyrophoric
- A chemical substance that will ignite spontaneously in air at or below a temperature of 130°F (54.4°C).
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