Lower explosive limit LEE

Solvent vapors cannot bum if the amount of air in the mixture is above or below the correct combustion ratio. If the amount of oxygen in the mixture is too small to support combustion due to a surplus of the fuel vapors, it is at the upper explosive limit (DEL) of the mixture. When the volume of the fuel in the mixture is too low to support combustion due to a lack of burnable vapors, it is at the lower explosive limit (LEE) of the mixture. It is necessary to ensure that these vapor-air mixtures are always below LEE or above UEE ratios. 

Table A1-4 (Flammability) is sorted first based on the type of each solvent in alphabetical order (acids, alcohols, aromatics...specials) second within types based on flash point — with the highest values first and third based on lower explosive limit (LEE) from highest to lowest. In other words, within type, solvents are sorted based on the ones with the least flammability risk bdng listed first.

The ventilation rate provided is a least four times the ventilation rate required to dilute the anticipated fugitive emissions to below 25% of the lower explosive limit (LEE), as determined by detailed calculations for the enclosed area. 

A fundamental solution to the dust explosion problem is to use a wet process so that dust suspensions do not occur at all. If a wet process can be used, it is one of the most satisfactory methods. However, the process must be wet enough to be effective. Some dusts with a high moisture content can still ignite. Dust concentrations in major equipment can be designed below the lower flammable limit, but this often cannot be counted on in operation. Dust concentrations cannot be safely designed to be above an upper flammable limit, because such a limit is ill-defined (Lees, 1980). For a large number of flammable dusts, the lower explosion limit lies between 20 and 60 g/m3. The... 

Flammable or explosive limits are the upper and lower vapor concentrations at which a mixture will burn or explode. LEE is the lower explosive limit and UEL is the upper explosive limit. 

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