There was a video of the civil war in Syria that showed men using a Soviet-era recoilless rifle. They were in a room and had aimed it out the window. The room was enclosed. After some chatter in Arabic, the men fired the weapon. What happened next was pure chaos. The recoilless rifle’s backblast turned that room into an instant of turmoil, causing damage to the walls and scattering everything about. Fortunately, the Soviet recoilless rifle was of a relatively small caliber. Having fired the 106mm recoilless rifle, I know darn well that its backblast confined to a room like that could have done serious damage to the crew as well as the back wall.
By the way, there is also footage out there of an Arab insurgent firing an RPG as one of his cohorts gets within three feet of the rear end. The firing knocked the man to the ground, possibly killing him.
A plain fact of bazookas, LAW M72s, anti-rank rocket launchers, TOW missiles and recoilless rifles is a backblast. These weapons do not have the recoil of conventional artillery. Instead, excess force is expended out the rear of the weapon. This is the backblast. Standing behind such a weapon can be fatal. In fact, I know of an account of men being trained to use a bazooka late in World War II. The loader did not move his head out of the way and was killed by the bazooka’s backblast.
Firing rocket launchers, RPGs and recoilless rifles requires having enough open space in back for the backblast to expend itself. This means that these weapons cannot be fired safely from enclosed spaces. There has to be open space. Firing from a foxhole or trench is possible if the rear of the weapon faces over the top of the hole. Firing from inside a bunker, a house, enclosed vehicle or average sized room is going to harm the firer and his pals more than the target. Unless they knock out some walls, soldiers in a house dare not shoot a backblasting weapon.
Many a diorama has been made foolish by placing bazooka men and recoilless rifles without consideration of backblast. Likewise, many skirmish rules for wargames do not account for it. They allow rocket launchers and recoilless rifles to be used from within bunkers and buildings. Realistically, a backblast area must be considered for both dioramas and game rules. Dioramas need a clear area behind the weapon. Game rules ought to forbid use of these weapons from houses, inside bunkers and other enclosed spaces.
(Rifle grenades like the ones used in the World Wars did not have a backblast. Panzerfausts did. Though the backblast of a panzerfaust was weaker than that of a bazooka, it was dangerous enough that a warning was placed on the weapon.)