topic Re: All-1-Sensor Not Recognizing Smoke/CO Detector(s) in Arlo Home Security System

All-1-Sensor Not Recognizing Smoke/CO Detector(s)

MG-ARLO-NM — Sat, 24 Jan 2026 16:48:15 GMT

My Arlo All-1-Sensors are not recognizing the T3/T4 sound from my First Alert Smoke/CO Detectors (First Alert 2-in-1 wired (SMCO100VAC) and 2-in-1 battery (SMCO210V)).

The All-1-Sensors are within 2' so I do not think it is a placement issue.

I, too, have been able to connect the All-1-Sensors to older plug-in CO detectors that emit the warning sound at a lower/different pitch. The newer First Alert detectors have a (much) higher pitch as well as voice commands (other threads indicate the voice command is not an interference).

As such, I think it has to do with pitch of the sound emitted by detectors.

I know a potential work-around would be to buy another (different brand?) battery/plug-in detector with a different pitch; however, this approach would not leverage the whole-home coverage of the interconnected wired detectors.

I, too, the All-1-Sensors do not have firmware updates.

I am open to any suggestions, comments, thoughts.

Re: All-1-Sensor Not Recognizing Smoke/CO Detector(s)

ShayneS — Tue, 27 Jan 2026 01:05:59 GMT

HI @MG-ARLO-NM

Thanks for reaching out, Can you PM me with the last four digits of the serial numbers of the affected devices?

Re: All-1-Sensor Not Recognizing Smoke/CO Detector(s)

jguerdat — Tue, 27 Jan 2026 15:05:47 GMT

As I recall, when I was testing the smoke/CO settings, I was unable to set them properly due to the combo detector sounds coming right after each other when pressing the detector test button. It seemed that I would have needed single detectors to make it work. I haven't tried to set that up since so maybe something has changed but I kinda doubt it.

@ShayneS can you verify any of this?

Re: All-1-Sensor Not Recognizing Smoke/CO Detector(s)

ShayneS — Fri, 27 Feb 2026 21:36:35 GMT

@MG-ARLO-NM

Just wanted to let you know I'm still waiting for feedback on this, and I'll be sure to provide more info as soon as that's received.

Re: All-1-Sensor Not Recognizing Smoke/CO Detector(s)

ShayneS — Fri, 10 Apr 2026 21:39:01 GMT

@MG-ARLO-NM

I have been in contact with the dev team regarding this and we would like to ask if you can try enabling the Smoke/co feature utilizing another method Instead of using the All-in-One Sensor to detect your smoke/CO combo alarms. Can you try enabling that detection directly on the Security sensor hub itself. Here's how you can enable this

In the Arlo app, go to your All-in-One Sensor settings and disable Smoke/CO alarm detection on the sensor.
Then go to your Hub/Base Station settings and enable Smoke/CO alarm detection there.
Once enabled, press and hold the test button on your First Alert combo detector and let it run for at least 2-3 full alarm cycles.

Please let us know if the hub successfully detected the alarm, and which detector you tested with.

Thank you!

Re: All-1-Sensor Not Recognizing Smoke/CO Detector(s)

ShayneS — Wed, 22 Apr 2026 15:42:24 GMT

@MG-ARLO-NM

Did you happen to receive my Reply above?

Thanks

Re: All-1-Sensor Not Recognizing Smoke/CO Detector(s)

ShayneS — Wed, 29 Apr 2026 21:04:45 GMT

@MG-ARLO-NM

Just following up again to see if you received my response.