The collaborative transport of objects between humans and robots is one of the main areas of focus in physical Human-Robot Interaction (pHRI). Ensuring the operator's safety and maintaining collision-free motion of the robot during transportation are crucial challenges in this context. Consider a collaborative co-manipulation scenario where the operator modifies the trajectory being executed by the robot. In such cases, the robot may deviate from its previously calculated path, potentially resulting in collisions. In this work, we propose a method to estimate the maximum collision-free volume around the path of the robot. This volume represents the permissible deviation introduced by the human worker while ensuring that no collisions occur. To evaluate the effectiveness of the proposed algorithm, we test it in a real industrial scenario.