At my company you can work up to 60 hours in any one stretch, but due to pay rules pretty much has to be 2x24's with a 12 back to back since you have to have a minimum 4 hour break after a 12hr shift before being allowed to work a 24 (apparently less than 4 hour break means you get the 12 hour pay rate for the follow on 24 hour shift which means 24 hours at double time pay, which I would love to get lol). My FTO and his partner didn't know the answer to the follow on question of how many hours after the 60 hour stretch before you're allowed to work again...
I suppose I should also mention our regular schedule not just the max allowed hours (since that's what everyone else is mentioning lol). There are multiple regular schedules, the 24 hour shifts are mirrored to the FD they work with (County fire being 7/8ths of our area.....those are a modified Kelley schedule, one 24 hour shift on, one off, one on, 2 days off, then another cycle of one on, one off, one on before a 4 dayoff period before the whole thing starts again. XOXOOXOXOOOO
http://www.fire.lacounty.gov/wp-content/uploads/2014/02/Shift-Calendar-2016.pdf Comes to roughly 2-3 shifts a week, 10 shifts a month). The remaining 8th of our 24hour shifts are on a 48-96 (days straight, 4 straight days off) so also about 2-3 shifts a week, roughly 10 shifts a month. 12 hour "Day Cars" all have staggered start times (so there are overnight day cars lol), most are M-W-F every other Sat, with the corollary Sun-Tues-Thurs every other Sat, and there may still be Sun-Mon-Tue every other Wed and Thurs-Fri-Sat, every other Wed. Either way 3-4 12 hour shifts a week.
So on a regular schedule, if you're on a 24 hour unit you can expect to work 48-72 hours in a week, and a 12 hour unit 36-48 hours a week (plenty of overtime available which is where the 60 hours max at any one stretch come into play) (12 hour units get straight time pay for the first 8 hours, time and a half the last 4 hours of shift, and double time if held over beyond 12, 24s only get time and a half after 40 hours in the week).