07-03-2025
I'm looking to replace my wired smoke detectors. What are my options?
Q: About 10 years ago, I replaced the original wired smoke alarms in my home with wired dual sensors that use both photoelectric and ionization technology. Because I've read that in-home smoke detectors should be replaced every 10 years, I have looked for replacements. But I've found just photoelectric detectors and photoelectric plus carbon monoxide detectors, which I don't need because we have stand-alone CO alarms. What is the best type of replacement smoke alarm to buy? I would like to add a battery-operated smoke detector in the garage. Can it be connected with the ones in the house? Also, I am considering internet connectivity for the alarm system. In a wired system, should each alarm be connected to the internet? Or do we need only one alarm to be connected to get alerts on our mobiles?
A: Your question about whether to get photoelectric or ionization detectors is easiest to answer. A new testing standard for smoke alarms went into effect in June that requires all new models to be good at sensing both smoldering fires and open flames. Before that, photoelectric detectors were better at sensing smoldering fires and ionization detectors were better at sensing flames. The difference was significant enough that the National Fire Protection Association recommended installing both types, leading manufacturers to make dual-sensing units. The distinction is no longer relevant as long as you buy sensors that are labeled as meeting the new requirements. The new rules also include a test designed to reduce false alarms: An alarm must stay silent when two hamburger patties are grilled 10 feet away.
Because finding dual-mode sensors isn't really an issue anymore, figuring out how to link a battery unit with wired-in alarms might seem like your biggest challenge. Numerous websites say flat-out that it's not possible and that only wired alarms can interconnect. That's outdated advice, too. First Alert and Kidde both make bridge units that allow a battery-only detector to communicate with wired-in detectors, creating the interconnected system you want.
The picture you sent shows that your current detectors are made by Kidde. Its bridge unit, P4010ACSCO-W, has only 1.2 out of 5 stars from customer ratings reported on its own website. The company is no longer making it, although some retailers may still have some in stock.
First Alert's bridge unit, the SA520B, has good reviews but is being replaced by the SM500-AC to comply with new electrical standards; these models are also listed with the same codes as a products from BRK, a sister company. The NFPA warns not to mix detectors from different manufacturers in an interconnected system because the way they communicate might be incompatible. Because you are planning to install new detectors throughout, switching to a different manufacturer is no issue, but if you were just trying to add a battery unit, you'd be wise to stick to one manufacturer or call your current company to ask about compatibility of a bridge unit from a different company.
If you go for First Alert's products, you could get the SM500V ($59.95 on the First Alert website) for the garage. This alarm runs on batteries and delivers warnings by voice. Note, though, that First Alert does not recommend installing a smoke alarm in a garage because of the risk of false alarms. But if you aren't starting a car or running equipment that generates smoke there, the warning probably wouldn't apply. The new battery-only detector should include 'wireless interconnect' as a feature, but that means it can connect wirelessly to a bridge unit inside your house, not to your phone.
For the bridge unit, which would link the battery unit in the garage to the other detectors in your house, you could replace one of the wired-in units with the SA520B or, when it is available, the SM500-AC. Finding these could be a challenge if you want to update your alarms soon. A First Alert customer-service representative said there is no estimate of when the new units will be available. The older model, SA520B, is sold out at many companies, although some online retailers still have it in stock. Elliott Electric Supply, which has dozens of stores in many states, had 256 units in stock earlier this week, although some stores had none. Call before you place an order. (The SA520B is described on some websites as a battery unit, but it has a way on the back to wire it in, which is what you'd need to do, after you turn off power at the circuit-breaker panel.)
For the other wired-in detectors in your house, you have numerous options, including the SM100V-AC, a photoelectric sensor with voice commands ($59.95), or the SMI100-AC, an ionization detector that also has voice commands ($34.95 on Amazon).
Could the combination of a battery unit in the garage and a bridge unit and wired-in detectors in the house also allow you to monitor the system from afar via cellphone? Not currently with First Alert products, said a customer-service representative who specializes in interconnectivity at First Alert. First Alert did make them, including a model designed to work with Ring, but no new ones are being made while the product is being redesigned. Kidde's Smoke Alarm with Smart Features also seems to have problems: On the company's website, more customers gave it one-star reviews (the lowest option) than gave it five stars. Kidde smart alarms that include air-quality monitoring have better reviews.
There are companies that make devices for linking alarms to home-monitoring systems accessible via phone using Z-Wave, a technology protocol that uses a different wavelength than WiFi, thus avoiding interference. The Zooz Z-Wave Plus Smoke and CO Detector Bridge, which lists for $34.95 at is one example. But study the technical details or contact that manufacturer to make sure it would work with whatever smoke alarms you buy. Installation instructions for the Zooz device suggest installing it at the last smoke detector in a wired system because that electrical box doesn't have as many wired connections. You would need only one bridge for the system.
You'd also need a compatible hub to receive the message. Zooz has tested Ring and ADT systems and verified they work. If you have a different home-security system, you'd need to call the company to make sure.
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