The short version
- A cooling fan is a part that wears out, and fans wear out fastest in extreme heat, which is when wildfires happen.
- A controller built around a computer has to start up after every power cut, and software updates can break things.
- FireShield has no cooling fan and no computer. Nothing inside a FireShield controller moves.
- It's sealed, so dust, water and insects can't get in, and there's no filter to clean.
- If you're comparing systems, ask whether there's a fan in it and whether it runs an operating system.
Wildfires usually come with heat, dry air and strong winds, and the controller on your house may be sitting in direct sun.
That's the day your system is there for, and the hardest conditions it will face.
A good question to ask about any system: what is most likely to be broken when you need it?
For most outdoor equipment, it's the cooling fan, and after that, the small computer the fan is there to cool.
The FireShield controller has neither.
The fan
A fan has a spinning part, and spinning parts wear out.
Fans wear out faster in heat, and a controller on the side of a house gets very hot in the summer sun.
A fan also needs vents, and vents let in dust, ash and insects. A filter helps, but filters need regular cleaning.
A fan is most likely to fail in extreme heat, and extreme heat is when wildfires happen.
FireShield left the fan out.
FireShield's patent says it plainly: the controller has "no fan or other moving cooling part," and "operates within a sealed, high-temperature enclosure." That requirement shaped everything else. With no fan, the processor has to be one that can handle the heat inside a sealed enclosure, so FireShield chose a chip for that, instead of choosing a fast chip and adding a fan to keep it cool.
Sealing the enclosure also keeps dust, water and insects out, and there's no filter to clean.
The computer
The second part FireShield left out is the computer.
A lot of control equipment is a small computer running an operating system, such as Linux. That makes it easier to build, but it causes three problems for a wildfire controller.
It has to start up. A computer can take up to a minute to start. During a wildfire the power can cut in and out, and each time the computer has to start over.
FireShield's controller restarts in a moment, not a minute.
Updates can break things. An operating system gets regular updates, and sometimes an update stops something that used to work. In a safety device that sits unused for years, you might only find out during a fire.
The patent is blunt about why FireShield went the other way: dropping the operating system "removes operating-system updates and the version dependencies among operating-system components, drivers, and libraries that can mismatch and cause failure or downtime."
The timing can slip. This matters most for the valves.
An operating system handles many jobs at once, so it can't always do one specific thing at an exact moment.
Valves need exact timing. The controller has to power each valve for the right amount of time to open or close it fully, every time.
So the FireShield controller runs simple software written for its chip, with part of the processor set aside just for the valves. The satellite radio has its own processor, so it can't interrupt a valve.
This kind of software takes more work to build. FireShield keeps all the settings stored on the controller, separate from the software, so your system can be adjusted without changing the software.
Lower power use
With no fan and no computer, the controller uses very little power, so it runs cooler, and cooler electronics last longer.
When the power goes out, the controller and the valves keep running on built-in backup power, and a controller that uses less power runs longer on it. There's more about power and internet outages in a separate article.
What to ask any company before you sign
Questions you can ask:
| Question | Why it matters |
|---|---|
| Is there a cooling fan? | If yes, it's a part that wears out, and it fails fastest in fire weather. |
| Does the enclosure have vents? | Vents let dust, water and insects in over the years. |
| Does it run an operating system? | If yes, ask how long it takes to start up after a power cut. |
| Can settings change without a software update? | With FireShield they can. It's a setting, not a software change. |
| How much power does it use on backup? | Less power means it runs longer on built-in backup power, with more left for the valves. |
Ask FireShield and other companies these questions.
You'll never see any of this working, and that's how it should be. A system like this has to work after sitting unused for years.
A fan can wear out, and an operating system can break with an update.
FireShield removed the fan and the operating system.
Next in this series
- The Setting You Can Change in Ten Seconds — Why FireShield's settings are stored separately from its software, and what that means when an installer wires a valve backwards.
- What Happens When the Cell Towers Go Down — How FireShield keeps working when the internet, the power, and the phone network are all gone.
- One Controller Fits Every House — Why FireShield builds one controller for every size of house.
- What Actually Has to Work When Nobody's Home — The whole system, start to finish, in plain English.
About FireShield — FireShield builds automated exterior wildfire defense systems for homes across Southern California. The controller described here is covered by FireShield's patent. See the wildfire defense system or talk to us.