Omega Block products are composed of non-toxic incombustible materials whose air permeability and relative fire-resistance characteristics are unequaled. Fully approved for constructing underground ventilation devices by MSHA, Omega Blocks reduce labor because they cover the area of 3 normal concrete blocks. Omega Blocks are easy to use because they can be accurately cut to size with a handsaw. A typical brattice stopping is dry stacked using alternating courses and then sealed with an approved sealant about the roof, rib and seams.