The iOS counterpart of Black Lung takes place in an underground mine shaft, like the original. The player is surrounded on all sides by mine tunnels, only two of them being open at the start of the mission. The room is stacked with chemical barrels with Nemexis on them, as well as large containers.
At round three, a large door opens behind the player.
At round six, a few more doors, to the left and right of the player, open.
At this point, MSG Ryan exclaims "Someone's at the door controls!". Every so often, Ryan makes comments like "Someone doesn't want you to survive this..." which suggests that somebody, possibly somebody from Nemexis, or someone from the opposite faction, whether that is the UAF or Warcorp, possibly Colonel Coleman, since he defected to Warcorp when Ryan is known to be with the UAF, is trying to kill the player to stop him from telling his tale.
At round eleven, three more doors around the player open, and Master Sergeant Ryan exclaims "Someone opened the door again! It was locked!"