I am installing Kidde brand smoke alarms in a new home. There are 16 smoke alarms and 1 carbon monoxide sensor that are all interconnectable to a maximum total of 18 untis according to Kidde. I have read that there should be no more than 12 smoke detectors interconnected. I am wondering if this is a "U.S. only" rule (I am in Canada) and what the reason is for this. I would think that it would be better to have all 16 units connected together. Anyone know more about this? Thanks!