In my current role we have scheduled breaks, which are to include anything 'personal'- smoking, eating, getting a drink, toilet time, checking your phone etc. Management are exempt from this rule.
In my previous role, no scheduled breaks, and I could take 2 additional smoke breaks a day. This wasn't specified in the contract, it wad just allowed.
However the same applied to anyone really, smoker or not. You could take 5 minutes out, generally, twice a day, in addition to the 30 min lunch. Whether that be to make a quick breakfast to eat at your desk, make a cuppa, take/make a personal phone call. Oh and unlimited toilet time! (I can't believe as an adult I have to appreciate going to the loo when I need to but thats another discussion
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It was very flexible, but no one took the piss and the workload didnt suffer.
Generally, people worked more than their hours anyway, coming in earlier, leaving later, lunch at their desks, which allowed for the flexibility.
I think smokers shouldn't be given special treatment tbh, either everyone gets the same level of flexibility or not.