I’m facing the same dilemma right now.

I have heat/smoke detectors tied into my Ademco Vista alarm panel and it’s monitored by a central station, so I have that covered. I do not, however, have any CO detectors.

Like you, I consider linked, hardwired detectors the way to go and I’ve identified some candidates. There’s also a Z-wave bridge that can tie to the signaling wire to communicate back to Home Assistant. I’m trying to decide what the value there is beyond being able to monitor CO levels when I’m not home.

Here’s the CO detector: https://www.homedepot.com/p/Gentex-Hardwired-Interconnected-CO-Alarm-with-Dualink-and-Relay-Contacts-CO1209F/202934253

Here’s the bridge: https://www.thesmartesthouse.com/products/zooz-800-series-z-wave-long-range-dc-signal-sensor

To further clarify, that’s carbon dioxide (CO2)–moderately inconvenient vs. carbon monoxide (CO)–deadly.

It’s a pump physically attached to a water heater that I’m controlling. The outlet and pump are both in the attic and that space gets up to 120° or more during the summer.

Unfortunately, yes. There are several critical loads on that circuit.