Common sense here, when over the years we've had various different people who worked for us and smoked. The rules for us where simple.
No smoking in van
No smoking on customers property
No dumping fAg buts outside a customers house or our house in morning!!!
A quick fAg when/if we (the boss) are collecting money from job is allowed but when the bosses are back, time to go no waiting to finish fAg!!!!
The last guy that worked for us who was a diamond actually used to ask if he could have a fAg!! A little too polite but he got it, as me or my business partner dont smoke why do we want to sit around and wait for him to have a "quick" 5 min fAg 10 times a day.
Funny little story here, many years ago the first lad we ever employed we never thought about smoking or mobile usage. A good few weeks after he started and was settled in, found him up a adder fAg in mouth on his mobile

to his bird!! LOL Well that stopped and smoking and mobile use was talked about!! Crazy!!