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The limiting oxygen concentration is shown in the lower right of the diagram. The limiting oxygen concentration (LOC), [1] also known as the minimum oxygen concentration (MOC), [2] is defined as the limiting concentration of oxygen below which combustion is not possible, independent of the concentration of fuel. It is expressed in units of ...
Toxic gases, by contrast, cause death by other mechanisms, such as competing with oxygen on the cellular level (e.g. carbon monoxide) or directly damaging the respiratory system (e.g. phosgene). Far smaller quantities of these are deadly. Notable examples of asphyxiant gases are methane, [1] nitrogen, argon, helium, butane and propane
Toxic: a chemical that has a median lethal concentration (LC 50) in air of more than 200 parts per million (ppm) but not more than 2,000 parts per million by volume of gas or vapor, or more than 2 milligrams per liter but not more than 20 milligrams per liter of mist, fume or dust, when administered by continuous inhalation for 1 hour (or less if death occurs within 1 hour) to albino rats ...
Lethal Concentration 50 [ edit ] LC 50 for acute toxicity on inhalation means that concentration of vapor, mist, or dust which, administered by continuous inhalation for one hour to both male and female young adult albino rats, causes death within 14 days in half of the animals tested.
Higher temperature or pressure, as well as higher concentration of the oxidizer (primarily oxygen in air), results in lower LFL and higher UFL, hence the gas mixture will be easier to explode. Usually atmospheric air supplies the oxygen for combustion, and limits assume the normal concentration of oxygen in air.
Examples include smoke or other poisonous gases at sufficiently high concentrations. It is calculated using the LD50 or LC50 . [ 1 ] The Occupational Safety and Health Administration (OSHA) regulation (1910.134(b)) defines the term as "an atmosphere that poses an immediate threat to life, would cause irreversible adverse health effects, or ...
For gases and aerosols, lethal concentration (given in mg/m 3 or ppm, parts per million) is the analogous concept, although this also depends on the duration of exposure, which has to be included in the definition. The term incipient lethal level is used to describe a LC 50 value that is independent of time. [8]
Mass transfer in a system is governed by Fick's first law: 'Diffusion flux from higher concentration to lower concentration is proportional to the gradient of the concentration of the substance and the diffusivity of the substance in the medium.' Mass transfer can take place due to different driving forces.