When it comes to search, door control (isolation) is not just for VES, it can be utilized during conventional operations as well. When searching ahead of the engine, immediate control of the entry door is paramount to [temporarily] preventing the intake of fresh air to the fire [until the arrival of a charged handline]; limiting its growth/spread and buying the search crew additional time. The practice of isolation can be employed throughout the duration of the primary search (whenever possible). By controlling the door upon entering each room, you effectively place a barrier between the space being searched and the fire - temporarily creating an area of refuge. Doing so blocks the flow of air and restricts additional heat, smoke and fire gases from entering the room.
Even a hollow-core door can provide a significant benefit in this instance. Although these doors possess a limited fire-resistance, they can drastically lower temperatures and gas concentration in the space being isolated. Additionally, once the door has been controlled, window venting [within that isolated area] becomes permissible, as there is no longer a pathway from the fire to the opening being created. This will discharge any pent-up heat and smoke within the room - lifting the thermal balance. As a result, the tenability of the space will increase, visibility will improve for those searching, and an alternative means of egress can be provided (eliminating the need to remove a victim through/past the fire area); collectively enhancing victim survivability.
Fredericks, Andrew. (2000, March). Little Droplets of Water: 50 Years Later, Part 2. Fire Engineering.