Hello Gary! This can't be set it can just be used to talk. You may though set alarms using a HomePod mini. If you have a HomePod, HomePod mini or any other AirPlay 2 speaker and a subscription to Apple Music (https://www.apple.com/apple-music/), you can use the loudspeaker as an alarm system in an automation in Home.
This automation only works in Home from Apple because developers like us do not have access to accessories that allow playback of TV, Apple TVs or the HomePod - only Apple can do this with the App Home.
Create an automation with a trigger from Eve Door & Window, Eve Window Guard, Eve Motion, Eve Cam (motion detection) or any other sensor and define when it should apply, such as time and/or presence/absence.
For the scene you select the HomePod and as audio source for example an alarm sound from the album Sirens Alarms and Horns (https://music.apple.com/de/album/evacuate-alarm/459056870?i=459057072) - done.
You can set the volume and duration of the alarm.
Best regards, Volker
Nov 8, 2022