When is it advisable to employ positive pressure ventilation (PPV)?

Employing positive pressure ventilation (PPV) is most advisable when there is a threat of fire spreading through open doors. In this scenario, PPV can help control the direction of smoke and heat, and create a more favorable environment for firefighting efforts. By pushing air into the structure, it effectively drives the smoke and heat out, making visibility for firefighters better and mitigating the risk of fire spreading through unimpeded openings. This proactive approach enhances both visibility and safety, benefiting both crews on the scene and potential civilians inside the structure.

Immediate employment of PPV upon arrival does not take into account assessment and safety considerations that need to be addressed first. Similarly, using PPV before entering a structure could pose risks if conditions are not properly evaluated, as it may complicate the situation without full knowledge of the fire's location and behavior. Additionally, waiting until after extinguishing the fire to utilize PPV would miss the earlier advantages of smoke and heat management, potentially allowing the fire to spread or complicating efforts to bring it under control. Thus, using PPV in conjunction with an identified threat of fire spreading is the most tactical and effective application of this technique.