radon alarm

https://theradonfannotworkingindex.cloudhinter.com/posts/what-to-do-when-your-radon-fan-is-not-working

That chirping from the basement is the radon alarm doing its job, alerting you to a colorless, odorless threat that can sneak into homes through cracks in the foundation. It's a sobering sound, reminding you to test levels and mitigate before this radioactive gas builds up to dangerous concentrations.