I called the Fire Department and asked if they would send someone out because my smoke detector/carbon monoxide detector, etc. was going off. I just wanted them to take a look at it, and they sent numerous fire trucks to my house. Why did they do that?

The Fire Department is required to send a certain number of trucks to the scene of any structure-related incident, based on the type of incident. Since we have no way of knowing the exact situation when we are dispatched, we have to assume that there is a fire or other emergency situation until we determine otherwise.