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Those with flash points above 37.8 °C/100 °F and below 93.3 °C/200 °F were classified as combustible liquids. [2] [3] Studies show that the actual measure of a liquid's flammability, its flash point, is dependent on the local air pressure, meaning that at higher altitudes where the air pressure is lower, the flash point is also lower.
Combustibility and flammability. A combustible material is a material that can burn (i.e., sustain a flame) in air under certain conditions. A material is flammable if it ignites easily at ambient temperatures. In other words, a combustible material ignites with some effort and a flammable material catches fire immediately on exposure to flame.
Divisions. Class 3: Flammable Liquids. A flammable liquid is a liquid having a flash point of not more than 60 °C (140 °F), or any material in a liquid phase with a flash point at or above 37.8 °C (100 °F) that is intentionally heated and offered for transportation or transported at or above its flash point in a bulk packaging.
Contains gas under pressure: may explode if heated H281: Contains refrigerated gas: may cause cryogenic burns or injury H282: Extremely flammable chemical under pressure: May explode if heated H283: Flammable chemical under pressure: May explode if heated H284: Chemical under pressure: May explode if heated H290: May be corrosive to metals
Lower flammability limit. The lower flammability limit ( LFL ), [1] usually expressed in volume per cent, is the lower end of the concentration range over which a flammable mixture of gas or vapour in air can be ignited at a given temperature and pressure. The flammability range is delineated by the upper and lower flammability limits.
A propane tank car after a fire, the HAZMAT 1075 symbol can be seen in red as a warning of the danger posed by the gas. A gas is a substance which (a) at 50 °C (122 °F) has a vapor pressure greater than 300 kPa (43.51 PSI) or (b) is completely gaseous at 20 °C (68 °F) at a standard pressure of 101.3 kPa (14.69 PSI).
The constant-pressure adiabatic flame temperature of such substances in air is in a relatively narrow range around 1,950 °C (2,220 K; 3,540 °F). [citation needed] This is mostly because the heat of combustion of these compounds is roughly proportional to the amount of oxygen consumed, which proportionally increases the amount of air that has ...
In the case of free expansion for an ideal gas, there are no molecular interactions, and the temperature remains constant. For real gasses, the molecules do interact via attraction or repulsion depending on temperature and pressure, and heating or cooling does occur. This is known as the Joule–Thomson effect.