alt Hacker NewsA light has to be seen, a siren has be heard. I bet email has a better chance of alarming the right person.
And you have to check those lights and sirens that they still work.
Everybody knew email was down.
The real problem is nobody thought of the consequences regarding the alarm system
Generally, for sensitive safety systems like this, Light and Siren are visible to those using the facility. So if problem developed, all patrons would be going "Umm, you know your sauna has flashing red light and siren going off?" after they all left the facility.
Yes, they still have to work but first off, both of those are extremely reliable systems, alarm circuits have extremely low risk of failure. Second, testing them takes 5 minutes a week/month, press the button, look for flashing light and listen to wailing noise.
It's inexcusable to think that email/slack or whatever is acceptable as anything other than notification system so people not in facility can be notified that alarms are going off.
EDIT: You are defending this setup and I'm not sure why. This seems email only setup seem indefensible.