Wireless Interconnected Smoke and CO Alarms

How it works

Each alarm carries a small radio. When one detects smoke or carbon monoxide, it broadcasts the event and every paired unit sounds, in some systems through a base station that can also notify your phone. Hardwired 'wire-free interconnect' units take mains power from the existing box and can relay between a run of old hardwired-interconnected alarms and new wireless ones. Pairing is done within one brand's system; mixed brands generally do not talk to each other.

Who needs it

NFPA 72 and US and Canadian building codes require interconnection in new homes, and wireless interconnection is permitted for retrofits in many jurisdictions. Practically, anyone in an older home with standalone alarms.

Codes, standards and listings

Canada

Smoke alarms are generally listed to CAN/ULC-S531 and CO alarms to CSA 6.19.

United States

Smoke alarms are generally listed to UL 217 and CO alarms to UL 2034. The X-Sense page we checked did not show a UL/ULC claim; check the model listing.

What the market looks like

Kidde sells a Wire-Free Interconnect range in hardwired (20SAR-VRF) and battery (20SDR-VRF) versions. X-Sense sells the SD19-W and XS01-WR; its US store listed the SD19-W at USD $18.99, but X-Sense says it does not ship to Canada, and the page we checked did not show a UL or ULC listing claim. First Alert / BRK sells the Onelink line. Google's Nest Protect was reportedly discontinued in 2025, which we could not confirm. We found no verified Canadian prices.

Features that actually matter

Radio interconnection

One alarm sounding sets off all of them. The safety case is simple: you hear a basement fire from a closed bedroom.

Hardwired bridge

Kidde's hardwired Wire-Free Interconnect models can join an existing hardwired interconnect, so you can extend an older system rather than replace it.

Combination smoke/CO units

Some systems include carbon-monoxide alarms on the same network, so a CO event also sounds throughout the house.

Phone notifications (some systems)

A base station can relay alarms to your phone. Useful when the house is empty; irrelevant to waking people inside it.

What it really costs

Up front

X-Sense SD19-W listed at USD $18.99 per unit on its US store. Other models: no reliable public figure. Budget per alarm across every level and bedroom.

Consumables

Batteries on battery models, per the manufacturer.

What else you'll need

An electrician for hardwired units. No reliable public figure.

Over five years

Mostly the purchase price; smoke alarms are replaced at ten years under NFPA 72.

Retail prices from public listings, October 2026; CAD where Canadian listings exist, otherwise converted at ~1.38.

How it differs from the alternatives

Versus hardwired interconnect

Wired interconnect is what new-build codes expect and does not depend on radio pairing. Wireless is the retrofit answer where wiring would mean opening walls.

Versus standalone alarms

A standalone alarm only warns the room it is in. Interconnection is the upgrade that matters most in an older house.

Brand lock-in

Choose a brand once and stay with it. Mixing brands breaks interconnection, and that decision follows you for ten years.

If not this, then what

• Hardwired interconnected alarmsThe new-build standard; worth doing during a renovation when walls are open anyway.
• Heat alarms for the garage and atticAdd-ons to the same system for the spaces where smoke alarms nuisance-trip.

Caveats

• Brand-locked ecosystems; mixing brands breaks interconnection.
• Google's Nest Protect was reportedly discontinued in 2025; we could not verify this.
• Listing status was not shown on every product page we checked.