Van type vehicle approaching fire
When the van type vehicle comes near the fire it will park in the middle of the tunnel releasing a large flow of gas into the balloons. After the balloons have fully expanded they will block the tunnel completely and the transport of oxygen towards the fire (together with other gasses) will be blocked.
Oxygen will be consumed
Due to the fire, oxygen will be consumed in the fire area and this will decrease the oxygen percentage in the blocked area between two van type vehicles parked at each side of the fire.
Free floating balloons
Even before the balloons are fully blocking the passage, other balloons are inflated with non combustible gas (CO2 or N2) and are set free in the fire area to reduce the volume with free air between the two bus type vehicles. These balloons will flow freely in the area between two bus type vehicles and will reduce the amount of free air. An other method is to inflate these free floating balloons with a compressor or ventilator that takes the filling gas from the fire area, this has the advantage that the fire area will not get “over-pressurized” by the extra added volume of gas.
After the passage has been fully blocked by the “blocking balloons” on the vans, gas from the fire area can be vented into inflatable objects, reducing the amount of free flowing gas, non combustible gas can be injected in the area while at the same time special fans on the vehicle will prevent the pressure increase in the “sealed of space”. Controlled combustion devices in the fire area together with the fire itself (if there is any) can reduce the oxygen percentage.
In the busses there will be “one way” pressure valves to assure that pressure in the fire area will not increase.
Corridor
The van type vehicles are of such a size that they can be used as an lock and has the possibility to guide persons through a corridor out of the fire area, while at the same time fire fighters and other emergency staff can enter the danger zone through a locker system that will not allow “new oxygen” to flow in the area of the fire(the van can even be prepared to allow small emergency and fire fighting vehicles passage). The van type vehicle is constructed in such a way that it will act as the mentioned passage lock.
Special preparation
Fire fighting in the confined space will need special preparation. Due to the low oxygen percentage people will need specific training. Also the vehicles that have to work in the enclosed fire zone need to be set up to work in low oxygen area’s. Electrical drive would be advantageous.
Having blocked the passage of air (oxygen), fighting and controlling the fire can be done in the traditional way with foam or any other means. Tests have shown that the fire will extinguish by it self due to the low percentage of oxygen. It is therefore of importance to have the sealing vehicles as close as possible to the fire area, in this way reducing the fire area to its minimum.
The method described has not been applied or tested under real circumstances yet.