Large underground caverns are commonly used in variety of applications. In many cases, because of the geomechanical limitations of dimensions and requirement of high volume, several parallel caverns are used. Plastic zone integration requires a larger rock pillar distance of theses adjacent caverns while eco-nomic and access reasons require smaller distance. In Iran many underground projects are located in West and South West. Asmari formation covers a large part of these regions. The stability of underground spaces that are constructed or will be constructed in this formation has been investigated. A proper cross section based on plastic analysis and a stability criterion has been proposed for each region. Finally, in each case, allowable rock pillar between adjacent caverns with similar dimension was determined with two methods (numerical analysis and fire service law). Results show that Fire Service Law uses a very con-servative safety factor and it was proposed to use a correction factor for allowable distance based on application of underground space.