Every body is different. Every body processes alcohol differently at different times. 

In many venues you will now be able to find a wall mounted breath-tester... STEER recommend using the device throughout the evening to monitor your alcohol levels. 

There are also many personal breath-testing devices on the market and some are better than others. STEER suggest you get a good one.  

IMPORTANT NOTE
Results from ALL breath-testing devices are indicative only and maybe subject to design, calibration and user operator errors. Readings given by breath-testing devices are not accepted by Police or the Courts. Your blood alcohol level can rise for one hour or more after your last drink. If you feel unsure about your ability to drive safely it is best to choose another transport option. 

-------------------------------     Alcohoot Personal Breathalsyer  ---------------------------

STEER recommend the Alcohoot personal breath-testing device. Purchase at
 www.alcohoot.com.au
and type in "STEER" to receive a 10% discount and 10% will also be donated by Alcohoot to the STEER Project.