1. A method for determining optimum positions in a region for a plurality of sensors, wherein the sensors are capable of detecting occurrence of a hazard in the region, comprising: a. simulating occurrence and movement over time of the hazard in the region to produce data representative thereof; b. simulating a reaction of sensors at a set of all possible candidate sensor locations in the region and for each of a plurality of sensor types responsive to the simulated occurrence and movement of the hazard over time; c. storing in a simulation cache data resulting from the simulated reaction of the sensors at the set of all possible candidate sensor locations in the region for each of the plurality of sensor types responsive to the simulated occurrence and movement of the hazard over time; d. selecting one of a plurality of candidate sensor solutions, wherein each candidate sensor solution comprises one or more sensors of one or more sensor types at corresponding selected ones of the candidate sensor locations within the set of all possible candidate sensor locations; e. retrieving from the simulation cache data for the selected candidate sensor solution from the stored data; f. evaluating the data retrieved from the simulation cache from said (e) retrieving with respect to performance criteria for the selected one of the candidate sensor solutions; and g. selecting another one of the plurality of candidate sensor solutions and repeating (e) and (f), the another one of the plurality of candidate sensor solutions differing from the one of the plurality of candidate sensor solutions in at least one candidate sensor location or at least one sensor type.