põlemispiiri

Põlemispiiri, also known as the flammability limit or explosive limit, refers to the concentration range of a combustible substance in an oxidant, usually air, within which a flame can propagate. Below the lower flammability limit (LFL), the mixture is too lean in fuel to burn. Above the upper flammability limit (UFL), the mixture is too rich in fuel, and there is insufficient oxidant for combustion to occur.

These limits are crucial for safety in industrial settings where flammable materials are present. Understanding and controlling concentrations within these limits is essential to prevent fires and explosions. Factors such as temperature, pressure, and the presence of inert gases can influence the flammability limits. For example, higher temperatures or pressures can broaden the flammability range, making ignition easier.

The LFL and UFL are typically expressed as a percentage by volume of the fuel in air. For instance, gasoline has an LFL of approximately 1.4% and an UFL of around 7.6% in air. These values are determined through standardized laboratory tests. Safety measures often involve maintaining concentrations well below the LFL or ensuring adequate ventilation to prevent the mixture from reaching the flammable range. Ignition sources must also be rigorously controlled in areas where flammable vapors might be present.