This happened to me a week or so ago. Unlike the OP, I searched for "Nest Protect false alarm" and was sent directly to this helpful page: https://nest.com/support/article/Nest-Protect-sounds-false-s...

After blowing the visibly-accumulated dust out of the interior everything was back to normal.

I wonder if the OP uses similar debugging tactics on servers that send alerts? "Hmm. 'CRITICAL: disk full' alert? Guess I'll hit it with a hammer until I stop getting paged."