[Ex Marking] q [Protection principle] Fine ground filling sourounds the ignition source so that an arc from inside the housing cannot ignite the surrounding combustable atmosphere [Method of protection] 
Sand filling
F l a m e p r o o f e n c l o s u r e
I n c r e a s e d s a f e t y
N o n s p a r k i n g
I n t r i n s i c s a f e t y
O i l i m m e r s i o n
P r e s s u r i s e d e n c l o s u r e
S a n d f i l l i n g