Let me be abundantly clear: This is a general guide. I don't know what your local building codes require. You should check them, since I didn't.

Despite a proclivity to starting non-destructive fires, I'm actually quite paranoid about unintentional fires. Southern California is a hotbed for wildfires, and we happen to live in a Very High Fire Hazard Severity Zone.1 Every year, the fire department encourages brush clearance via threats of fines and exorbitantly high removal fees. And yet an alarmingly highly number of my neighbors still have wood shake rooves covered in pine needles, despite Los Angeles banning them in 1989.2 Burbank is actually making people remove them,3 while my neighbors ignore maintenance to avoid triggering replacement requirements. So how do I sleep in this tinderbox neighborhood? Smoke alarms! Smoke alarms EVERYWHERE!

There are two different types of smoke detector sensors - photoelectric and ionization. The National Fire Protection Association recommends using a combination of both.4 There are dual sensor detectors, but only one of the sensors has to pass to get the unit certified.5

There are also different ways to power alarms: high-voltage, low-voltage, and batteries. If you have user-replaceable batteries, change them every six months. I put a reminder on the calendar and change every single one at the same time. If one alarm decides it wants to have its batteries replaced early, it still gets the regularly scheduled replacement. Saving an extra battery or two is not worth the hassle it would become after a few years.

Speaking of replacements, the actual alarms need to be replaced about every ten years. Each unit should have a replacement or manufacturing date. Again, I recommend changing every unit at once.

You know that little "TEST" button that you are supposed to hit once a month to deafen yourself? Well, the good news is it tests the alarm. The bad news is it doesn't actually test the sensor. Smoke, like that sold in aerosol cans, is the only way to test the smoke sensor.6

Some alarms can be interconnected, either wired or wirelessly. If one senses smoke, they all go off, making them better at alerting occupants.7 Usually only alarms from the same company will talk to each other.

There are other features, such as internet connectivity, built-in carbon monoxide detectors, and easily accessible battery compartments that don't require taking the entire damn thing apart. Our house sports heat detectors interconnected with the smoke detectors,8 though we narrowly escaped installing the residential fire sprinklers required for new builds in California.9 If our landscape sprinkler system ever gets fixed, we'll probably get a controller that also connects to the smoke detectors so the grass doesn't get charred.

My final recommendation is to clean your dryer vent and duct. Lint gets past the screen and builds up over time, creating a fire hazard.10