There are some clear situations where mixed gas should be used for dispensing Beer to avoid disaster.

• If you are serving a ‘nitro’ beer, a beer that has nitrogen brewed in it or added to it. Guinness is a good example of this style.
• If you are serving beer at a pressure over the balance point for that beer. In other words you need to dispense at a higher pressure than the beer desires, in which case you will over-carbonate it.
• For ‘nitro’ beers, CO2 gas alone will allow the nitrogen to come out of solution and nitrogen alone will allow the CO2 gas to come out of solution. So to keep the beer in equilibrium the correct mix of CO2 and N2 is required.

The higher the N2 content in the brewed beer the more N2 needed in the mix used to keep and dispense it.

For non 'nitro' beers there is a different situation. All beers have an as brewed CO2 content, quoted in volumes or grams per litre. This level is selected by the brewer, and it has an effect on taste and appearance. The correct gas mix will keep the balance of the beer. The CO2 part of the mix will help maintain the as brewed volumes and the nitrogen part of the mix will help provide the pressure necessary to dispense it. By looking at the dispense temperature and the dispense pressure an appropriate mix of CO2 and N2 gases is selected.