If you make a profile where all the ringers are silent the alarm should still work...if you're talking about calendar alerts then there's an option when you edit a profile to make those loud or not. The profile shouldn't affect the alarm- if it's set, it'll go off.
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Put your ringer profile on "OFF" and set your alarm. It works. I do this all week because I do not want to hear my phone go off in the middle of the night or an alarm for my email or SMS. I have to get up at 4 a.m. M-F and the last thing I need is my phone to go off while I try to sleep. So yes it does work.