Hi. I am a simmer as well and I will be honest, fires are extremely common in the Sims, especially the Sims 4. In Sims 3 and Sims 2, and even in the original Sims, it is very common that with the smoke detector the fire department workers will show up. My one theory is that in Sims 4, a sim must put out their own fires (which I honestly find quite frustrating) and even with a smoke detector, I do not believe the fire department workers would show up. This may be exactly why you were waiting and they never showed up. If you check the job icon, also, you may notice that a fireman/woman is not an option. So I will make it clear for you, no, this is not a glitch, as you may have figured. There luckily is a way to save your house and sims from a fire, an incredibly easy way, too. When a sim discovers a fire, the first thing they do is panic, but you can simply click on the fire and there should be an option to put it out. Your sim does not need any items or skills to do this, they should just do it automatically. And no, sims that are younger than a teen: (child, toddler, baby, pets) cannot put out fires, and it's sort of obvious. Also, toddlers, babies, and pets cannot die from fires, even though pets can catch fire (but they can't die from it.) Children, teenagers, young adults, adults, and elders surely can die from fire in the Sims (this includes any pregnant sims). Teenagers and older can put out fires, so if a fire starts while a sim within that age group is not home, you're basically out of luck. Therefore, this is not a glitch, and is really an easy fix. If a fire does start while your sim is not home, you can quickly send them home early from school or work to put the fire out. I hope that this was helpful to you or anyone else.