Yes, a single infraction will result in a 3 day suspension. However to reiterate, unless it is a severe violation, you will always receive a warning before receiving an infraction.
Just to be clear, a single infraction will result in a suspension?
Edited to add: Do warnings have a time limit in which they expire?
Warnings do not have a time limit/expire but this doesn't mean you couldn't receive more than one warning before getting an infraction.