Blind Grenade

Models may not see through, or into, or out of, the blind marker. Models may not use targeters or infra-vision to see through the marker. Psykers may not see or use their powers through the marker. 
Any models within the blind cloud have the choice of remaining stationary, or moving at half rate in a random direction.Models in  hand-to-hand combat within a cloud may fight, but as they are completely blinded they  halve their Weapon Skill rounding  up.
See Wargear Rulebook pg. 56 for further rules