Heiman Smart Carbon Monoxide Alarm (C1-M)

Quick verdict

Carbon monoxide alarms have been slow to get the smart home treatment, and Heiman is among the first to bring one to market with Matter over Thread. It works with Home Assistant, Apple Home, Google Home, and Alexa, all locally. The built-in alarm sounds regardless of your network status. It is also certified under Works with Home Assistant, which is rare for a CO alarm. Check the SKU before you order: the US/Canada part is the C1-M and the Europe/China part is the HS-720ES-M, and the similarly named HM-720ES and WS-720ES in the same series are not Matter devices at all. If you have been waiting for a CO alarm that integrates into your smart home without cloud dependency, this is one of the first viable options.

Standout: Among the first Matter over Thread carbon monoxide alarms available, and certified under Works with Home Assistant.

Notes last checked Oct 20, 2026.

Compatibility snapshot

Why it stands out

• one of the first Matter-native CO alarms on the market
• works across all major smart home platforms via Matter
• standalone alarm function works independently of your network. Safety first

Reasons to hesitate

• requires a Thread border router for smart home integration
• CO alarm support in Matter controllers is still relatively new
• less brand recognition than traditional safety brands like First Alert or Kidde
• two regional SKUs with the same name: the C1-M is the US/Canada part and the HS-720ES-M is the Europe/China one, and the sibling HM-720ES and WS-720ES in the same series are sub-GHz and Wi-Fi rather than Matter

Best for

• users who want a cross-platform smart CO alarm with local-only operation
• early Matter adopters building a Thread-based safety network

Avoid if

• you want a CO alarm from a legacy safety brand with decades of track record
• Matter CO alarm support on your preferred platform is not yet mature

Privacy and local-control notes

Fully local Matter over Thread device. No cloud account or internet connection required.

Home Assistant support: supported · integration path: Matter.

Buying reality check

Price notes: The C1-M read $47.99 in the Amazon buy box on 2026-10-21, which is mid-range for a smart CO alarm and carries Matter cross-platform support on top.

Compare side by side: see smoke alarm comparisons →

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