I think it depends upon the circumstances. If you're in a very heavily wooded area close to big buildings, you will get very poor data. In fact you could get huge numbers of false alarms. So it's very situation-dependent, and it's hard to come up with just one number for the false alarm rate. You need to say, “In this circumstance, this is the false alarm rate that we had expected. In this circumstance it would be higher. In this circumstance it might be lower.” So it's very dependent, and getting one number to describe it across the entire spectrum of possible circumstances would be very difficult.
On February 14th, 2012. See this statement in context.