Without getting into a big discussion on this point, the operative word here is "EMERGENCY". The 911 system and the emergency room at the hospital were designed for emergencies. Of course, the definition of an emergency varies and I am sure everyone understands this. If you think it is an emergency, then by all means call 911. However, a whole lot of things that clearly arn't emergencies eat up a lot of resources. When people complain about public service response times, ER wait times, the attitudes of the people working at these jobs, accidents and mistakes involving the people in these jobs, keep in mind that a lot of this is caused by the mind numbing experience of dealing with people who believe that these people exist as their doormat.
Broken bones and lacerations requiring stiches are considered emergencies in our society. The emergency doesn't have to be life threatening to be considered an emergency.
If you need the battery in your smoke detector changed, this isn't an emergency and IMO you should not call 911.
A disabled car in the middle of the freeway is an emergency in my book: the potential for a accident is high and people will surely be injured or killed.
Adjusting your thermostat is not an emergency and IMO you shouldn't use 911 for that.
Just use some common sense. Here where I live we have a non-emergency 311 number. And we (the fire department) will respond on virtually anything: if you call, we will come: even if the guys on the truck have no idea why or what we are supposed to do, we will respond. But, 311 doesn't get used a whole lot because everyone considers their problem to be of vital importance. So, when the closest unit to you is discussing your ingrown toenail with you, they arn't available to respond to the baby that fell in a pool on the next block. Their response will be delayed.