Slipping of ropes are a problem that will cause the object being lifted to fall back to earth. If the pulley is hand operated (i.e., the rope is being pulled by hand), slippage can cause injury since the operator will now be lifting the entire weight of the heavy object.
A pulled muscle or rope burn, from the rope being ripped from the hand, will cause possible injuries, not to mention dropping the casualty being rescued.
Some rescue kits have rope grabs that are attached to the pulling rope, these must always be attached to the rescuers harness, in case of a slip or loss of control of the pulley system, it will auto lock and prevent loss of control.
Hauling through an overhang
This is potentially one of the most dangerous things that can happen on a vertical rescue. If a patient that is either in a stretcher, free hanging alone or hanging with a rescuer, is pulled up tight under an overhang, roof or trapped or wedged on something during a haul, then the results can be catastrophic.
The rescue kit has great powers of mechanical advantage and can quickly and easily break a rescue line.
It is also possible to severely injure the rescuer or patient. It is imperative that the patient is fully enclosed in a stretcher and there are no obstructions in the path - a finger or arm caught between the metal edge of a stretcher and a building could be torn away if pulled through a small overhang. The rescuer must take care never to place any part of his/her body in a position where it could be jammed and damaged.
Effective communications. In the absence of radio communications ("coms"), "coms relay" people must be positioned on rope/s to maintain a visual and verbal link with the rescuer/patient.
Rescuer must have a whistle - a single long blast means STOP.
Rescuer can call for a STOP just before the overhang if repositioning is re-quired, in order to successfully manage the passing of the overhang.
Silence at the rescue site is imperative - so that a STOP command or whistle signal is heard by the hauling team.
The rescuer or patient must never place themselves in a position where they can be jammed between the stretcher and the building or overhang.