Smoke and CO usually refers to a combination smoke and carbon monoxide detector —a 2‑in‑1 safety device that alerts you to both fire and carbon monoxide gas with one unit.

What “smoke and CO” means

  • It is a single alarm that includes a smoke sensor (for flames/smoldering fires) and a CO sensor (for carbon monoxide, an invisible, odorless gas).
  • These devices are marketed by major safety brands (First Alert, Kidde, SimpliSafe, ADT, X‑Sense and others) specifically as “smoke & CO” or “smoke and carbon monoxide” alarms.

Why people use them

  • They save space and outlets by combining two required alarms into one, making it easier to meet building and safety code recommendations on every level and near bedrooms.
  • Modern models often add features like 10‑year sealed batteries, hardwire plus battery backup, voice alerts that tell you if the danger is smoke or CO and sometimes app or professional monitoring integration.

Quick safety pointers

  • Install on every level of a home and near sleeping areas; brands explicitly advise “every level, every bedroom” for combination units.
  • Keep them a bit away from cooking appliances (often at least about 10 feet) to reduce nuisance alarms from regular cooking smoke while still catching real fires.

Information gathered from public forums or data available on the internet and portrayed here.