September 2024 | AIChE

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September 2024

Limiting Oxidant Concentration (LOC)

The concentration of oxidant, in a fuel-oxidant-diluent mixture below which a deflagration cannot occur under specified conditions. The LOC is synonymous with the term Minimum Oxygen Concentration (MOC).

Limiting Conditions for Operation

Specifications for critical systems that must be operational and critical resources that must be available to start a process or continue normal operation. Critical systems often include fire protection, flares, scrubbers, emergency cooling, and thermal oxidizers; critical resources normally...

Limit Dose

The upper limit dose used in testing (2000 5000 mg/kg)

Likelihood

A measure of the expected probability or frequency of occurrence of an event. This may be expressed as an event frequency (e.g., events per year), a probability of occurrence during a time interval (e.g., annual probability) or a conditional probability (e.g., probability of occurrence, given that...

Life Cycle

The stages that a physical process or a management system goes through as it proceeds from birth to death. These stages include conception, design, deployment, acquisition, operation, maintenance, decommissioning, and disposal.

Level of Concern

The concentration of an airborne chemical above which there may be adverse human health effects experience as a result of a short-term exposure during an episodic release.

Level of Acceptable Practice

Good, successful, common, or best practices in PSM that have evolved, either through common and successful usage, interpretation by regulators, or in clear and measurable reductions in process safety risk, into informal criteria that are used by industry and by regulators to define acceptable...

Lethal Dose 50 (LD50 )

A single dose of a material which on the basis of laboratory tests is expected to kill 50% of a group of test animals. The LD50 dose is usually expressed as milligrams or grams of material per kilogram of animal body weight (mg/kg or g/kg). Importance: Both are measures of the toxicity of a...

Lethal Dose (LD)

A concentration of a substance being tested which will kill a test animal.

Lethal Concentration 50 (LC50)

The concentration of a material in air which, on the basis of laboratory tests, is expected to kill 50% of a group of test animals when administered as a single exposure (usually 1 or 4 hours). The LC50 is expressed as parts of material per million parts of air, by volume (ppm) for gases and vapors...

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