September 2024 | AIChE

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September 2024

Positively Buoyant Gas

A gas with density less that of air at ambient temperature.

Positive Material Identification (PMI)

The determination of the materials of construction of an equipment item or component (e.g., piping).

Portable Building

Rigid structure that can be easily moved to another location within the facility.

Pool Fire

The combustion of material evaporating from a layer of liquid at the base of the fire.

Polymerization

A chemical reaction in which one or more small molecules combine to form larger molecules. A hazardous polymerization is such a reaction which takes place at a rate which releases large amount of energy.

Poison, Class B

A DOT term for liquid, solid, paste, or semisolid substances-other than Class A poisons or irritating materials-which are known (or presumed on the basis of animal tests) to be so toxic to man as to afford a hazard to health during transportation. Importance: If a substance is known to be a poison...

Poison, Class A

A DOT term for extremely dangerous poisons, that is, poisonous gases or liquids of such nature that a very small amount of the gas or vapor of the liquid, mixed with air is dangerous to life. Some examples: phosgene, cyanogen, hydrocyanic acid, nitrogen peroxide.

Plume Rise

Rise of plume in elevation above source due to buoyancy or momentum.

Plume

A visible or measurable discharge of a contaminant from a given point of origin that can be measured according to the Ringelmann scale.

Plosive Density

A chemical group contribution method for predicting the chemical instability explosion potential of a material.

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