Concentration of Explosive substance  

Lower Explosion Limit (LEL): 

The lower explosion limit is the concentration of a mixture,  
that is not yet combustible  
(mixture is too less) 

Upper Explosion Limit (UEL): 

The upper explosion limit is the maximum concentration of a mixture, that is still combustible  
(mixture is too fat) 

Flash Point of Explosive Substance  

  • Flash point is the lowest temperature at which a liquid can gives off vapor to form an ignitable mixture in air near the surface of the liquid. The lower the flash point, the easier it is to ignite the material. 
  • For example, gasoline has a flash point of approximately -40°C and is more flammable than Diesel which has a flash point of 55 °C