põlemispiire

Põlemispiire, also known as the flammability limits or explosive limits, refers to the range of concentrations of a flammable gas or vapor in a mixture with air or another oxidant at which ignition and self-sustained combustion can occur. Below the lower põlemispiire, the concentration of the fuel is too low to support combustion, and the mixture will not ignite or sustain a flame. Above the upper põlemispiire, the concentration of the fuel is too high, and there is not enough oxidant (typically oxygen) to support combustion.

The põlemispiire are usually expressed as percentages by volume. For example, methane has a lower põlemispiire of approximately 5% and an upper põlemispiire of approximately 15% in air. This means that a mixture of methane and air containing between 5% and 15% methane by volume will be flammable.

Factors such as temperature, pressure, and the presence of inert gases can influence the põlemispiire. Higher temperatures and pressures generally widen the flammability range, making combustion easier. The presence of inert gases, like nitrogen, dilutes the mixture and can shift the põlemispiire, often narrowing the flammable range.

Understanding põlemispiire is crucial for safety in industrial settings where flammable materials are handled. It helps in designing ventilation systems, explosion protection measures, and establishing safe operating procedures to prevent fires and explosions. It is a fundamental concept in fire science and chemical safety engineering.