Põlevuspiireid

Põlevuspiireid, often translated as flammability limits or explosive limits, refers to the range of concentrations of a combustible gas or vapor in an air mixture within which ignition and sustained combustion can occur. Below the lower flammability limit (LFL), the concentration of the fuel is too low to support combustion. Above the upper flammability limit (UFL), the concentration of oxygen is too low to support combustion, or the fuel concentration is so high that it acts as a heat sink.

The LFL and UFL are critical parameters in fire and explosion safety. For a given flammable substance, these limits are typically expressed as percentages by volume in air. For example, methane has an LFL of 5% and an UFL of 15% in air. This means that if the concentration of methane in air is between 5% and 15%, an ignition source could cause an explosion. If it's below 5% or above 15%, it will not burn or explode.

Factors such as temperature, pressure, and the presence of inert gases can influence these limits. Higher temperatures and pressures generally widen the flammability range, making ignition easier. The presence of inert gases, like nitrogen, dilutes the mixture and can narrow or eliminate the flammability range. Understanding and controlling substances within their põlevuspiireid is fundamental for preventing fires and explosions in industrial settings, laboratories, and domestic environments.