Re: NOT an urban legend
I do pause at "Would not believe it if I had not read it." In the "urban legend" usual version* it's a cleaner who does it.
I'd expect any mains medical appliance to bleep when it goes onto battery, but there are possible reasons that that wouldn't be noticed or attended to. On the other hand, the COVID-19 intensive care ward is not going to welcome visitors. Not now anyway. And if this is a true "ventilator" then the patient is kept unconscious and not really worth visiting, but the term may also be applied to different types of oxygen supply machine.
I had the school admin server that went onto battery and shut down before making its overnight backup for a while (we didn't want it to shut down at all), because the "janitor" in role of watchman had got it into their head to save turning off lights one by one by just turning off the whole building.
* https://www.snopes.com/fact-check/polished-off/ "arranging for an electrician to fit an extra socket"
Biting the hand that feeds IT
