The legal limits are different for different types of driving licenses and also for differnet countries.
Below are the current UK limits (excluding Scotland which is now lower)For vehicles operated on a normal driving license
Blood test - 80 milligrammes of alcohol in 100 millilitres, 80mg/ml, 0.08 BAC, 0.8 Promille
Breath Test - 35 microgrammes of alcohol per 100 millilitres of breath BrAC
For all professional drivers and operatives.
Under the new Railways Transportation Safety Bill the Government have now introduced new limits for those working in the Transport Industry. The new limit is just 0.02% - one quarter the UK Drink-Drive limit of 0.08% and the lowest detectable level possible allowing for the residual levels that can exist in anyone whether they've been drinking or not. The new rules also apply to Pilots, Cabin Crew, Air Traffic Controllers, Aircraft Engineers, Train Drivers, and Commercial Seamen.
Blood test - 20 milligrammes of alcohol in 100 millilitres, 20mg/ml, 0.02 BAC, 0.2 Promille
Breath test - 9 microgrammes of alcohol per 100 millilitres of breath (BrAC) More information on legal limits including Scotland and Europe