the schematic representation of fig1 shows an example of the basic functioning of the method according to the invention including the associated control and measurement systems . the piping is thereby depicted as thick bold lines and the measurement / control lines are depicted as normal thin lines . the inert gas can be released from the inert gas source 2 , through a valve 3 a , and one or more outlet nozzles 6 a into protected area 1 a . the inert gas source can hereby be of diverse design . a typical arrangement is to provide the inert gas from one or a plurality of containers , for example steel cylinders . alternatively , a generator can be used to produce an inert gas ( nitrogen , for example ) or an inert gas / air mixture . it is also conceivable for the primary gas source to be redundantly configured for the purpose of increasing safety ; i . e ., a secondary inert gas source is accessed as needed which consists in turn either of compressed inert gas in steel cylinders or comes from an inert gas - producing generator . the concentration of the inert gas in protected area 1 a is regulated by control unit 4 which in turn acts on valve 3 a . control unit 4 is set such that a base inertization level is reached in protected area 1 a . this base inertization level reduces the risk of fire or explosion in protected area 1 a and is maintained by introducing inert gas into protected area 1 a from inert gas source 2 through valve 3 a and inert gas inlet nozzle 6 a . in the event this system arrangement should fail — if , e . g ., valve 3 a does not close or the generator producing the inert gas or the inert gas / air mixture does not switch off , and thereby continuously allows inert gas to enter the protected area through inert gas inflow 6 a , with the inert gas concentration thereby continuously rising in the protected area such that the oxygen content falls far below the desired base inertization level — the following mechanism according to one embodiment consistent with the present invention , is set in motion . upon control unit 4 measuring an oxygen concentration which is too low , by means of oxygen sensor 5 a , control unit 4 emits in consequence thereof , a signal to close valve 3 a or a signal to shut off the generator producing the inert gas or inert gas / air mixture . once these two conditions are met and the oxygen concentration in protected area 1 a falls even further , which can also be signaled to control unit 4 by inert gas sensors 12 a , the fresh air supply system 8 a is activated , releasing additional fresh air into protected area 1 a by way of one or more fresh air supply inlets 7 a . the inflow volume of fresh air is thereby set such that even at maximum operation of the inert gas - producing system ( configured either as gas cylinders or a generator ), the inert gas concentration in protected area 1 a cannot continue to rise . this therefore ensures the desired oxygen concentration in protected area 1 a , even if the control unit governing the inert gas inflow into protected area 1 a should fail . fires are thus reliably prevented and yet people can still remain in protected area 1 a as need be without fearing any adverse effects . fig2 depicts an exemplary embodiment of a sequence to the oxygen concentration in protected area 1 a . the oxygen concentration is regulated to a base inertization level ( target value ), between an upper and a lower target value . the inert gas source is activated and inert gas introduced into protected area 1 a at time point t o . as a result of this introduction of inert gas into protected area 1 a , the oxygen concentration drops between time points t o and t 1 . the inert gas source is again deactivated at time point t 1 . the oxygen concentration continues to slowly rise again up until time point t , because , e . g ., some fresh air enters the protected area due to leakage relative to the ambient air . thus , the inert gas source is re - activated at time point t 2 . should some defect prevent the inert gas source from being deactivated , however , the oxygen concentration would continue to drop in the protected area . the maximum inertization concentration allowed for protected area 1 a and which is still safe for people is reached at time point t 3 . should the inert gas system malfunction ; i . e ., an unhindered continued inflow of inert gas moves into the protected area — the oxygen concentration will continue to drop past time point t 3 , which would make the protected area unsafe for human occupancy . by means of the controlled inflow of fresh air according to one exemplary embodiment of the present invention , starting at time point t 3 , there is no drop below the maximum inertization level ; i . e ., the oxygen concentration in the protected area remains above the maximum inertization level . an emergency alarm ( not shown in the figure ) can also be provided , to be triggered at any time point . the base inertization level at which fires are reliably prevented is re - attained at time point t 4 . in order to maintain protection against fire , the fresh air supply is switched off again at time point t 4 . fig3 shows a further exemplary embodiment of the present invention of an inertization system which in this case includes two protected areas 1 a and 1 b and zone - specific inertizing and monitoring components . protected area 1 a is monitored in this case according to the details as given relative the description of fig1 and 2 . a further protected area 1 b with associated inertizing and monitoring components is additionally depicted . said components encompass valve 3 b , inert gas inlet 6 b , oxygen sensor 5 b , fresh air supply inlet 7 b and the fresh air supply system 8 b . alternatively , the control unit 4 depicted in fig3 could also consist of two separate control units . the two protected areas 1 a , 1 b are separated from one another by a wall 9 . alternatively , the control unit 4 depicted in fig3 could also consist of two separate control units . protected area 1 a , to which people do not have access in this exemplary embodiment has a different ( higher ) inertization level than protected area 1 b which , despite inertization , has people coming and going on a regular basis . protected area 1 a could have an inertization level at which the oxygen concentration is at 13 % by volume , for example . in contrast thereto , control unit 4 ensures a different inertization level for protected area 1 b , for example with the oxygen at 17 % by volume . because of the permeableness of wall 9 , inert gas could pass uncontrolled from protected area 1 a to protected area 1 b . this is depicted in fig3 by directional arrows 10 . the function of control unit 4 is to guarantee the different inertization levels in protected areas 1 a and 1 b by supplying inert gas through valves 3 a and 3 b and supplying fresh air as necessary through the fresh air systems 8 a and 8 b and the fresh air supply inlets 7 a and 7 b , as was detailed in the description relative to fig1 . valves 3 a and 3 b are also referred to as zone valves in this case since the different protected areas 1 a and 1 b constitute different monitored areas . it should be emphasized that the above - described embodiments of the invention are merely possible examples of implementations set forth for a clear understanding of the principles of the invention . variations and modifications may be made to the above - described embodiments of the invention without departing from the spirit and principles of the invention . all such modifications and variations are intended to be included herein within the scope of the invention and protected by the following claims .
an inertization method for preventing fire or explosion in a first enclosed protected area by lowering the oxygen content in the protected area to a base inertization level relative — to the ambient air . with the objective of eliminating any danger to people or processes within the protected area , the method according to the invention provides for measuring the oxygen content in the protected area , comparing it to a threshold , and in the event it falls below the threshold , introducing fresh air into the protected area .