Different CO2 grades?

[balvey]

The easiest way I have found to purge the keg (and know that I have all the O2 out) is to fill the keg with starsan, purge the minimal head space, then push the starsan out of the tap with CO2. In the end, I have a santized and CO2 filled keg ready for filling.

hmm... so how do you get that little bit star san out of the bottom of the keg?

[LoganO]

You can just flip the keg upside down and pull the relief and left the small amount of star san run out and sanitize the relief while doing so.

[TheTodd]

The easiest way I have found to purge the keg (and know that I have all the O2 out) is to fill the keg with starsan, purge the minimal head space, then push the starsan out of the tap with CO2. In the end, I have a santized and CO2 filled keg ready for filling.

hmm... so how do you get that little bit star san out of the bottom of the keg?

You can just flip the keg upside down and pull the relief and left the small amount of star san run out and sanitize the relief while doing so.

Or don't worry about it. The few ounces of StarSan left in the bottom will not have any effect on your beer.

[PhillyBrewer]

So does the overwhelming majority purge their kegs before filling them?

[Grist Licker]

You can get the last drop of starsan out of the bottom of the keg if you (1) make sure your beer out dip tube is sitting in the the divot in the bottom of the keg before adding starsan, (2) after pushing out the starsan with co2, let keg sit for 5 minutes to let all liquid run down the sides and into the divot below your diptube, (3) pressurize the keg to around 30psi, (4) "burp" the keg by pushing on the beer out poppet a few times. 30psi will blow dry the bottom of your keg in a hurry.

[Airedale98]

There are grades of CO2 but if you're using a reputable shop -there should be no issue. I work for Airgas, not the division that manufactures CO2 but here's a bit on the subject from their website;
What are the uses of Carbon Dioxide(CO2)?

Carbon Dioxide is used as a refrigeration gas, as a blanketing gas for chemical reactions and other applications requiring a chemically inert gas. The Bone Dry and Anaerobic Grades of Carbon Dioxide are used as atmospheres for anaerobic incubation in microbiology labs. Coleman Instrument Grade is a carrier gas for the Coleman Oxygen Analyzer. Medical carbon dioxide is used for various medical purposes, such as in its liquid phase, where it provides sub-zero temperatures for cryotherapy or other surgical practices.

Good Brew to All!

[jimmiec]

Our local Airgas switched to food grade CO2, which means I have to leave my tank overnight. CO2 is CO2 but how does a supplier know what gas is in your tank when you bring to be refilled. Is the provider of CO2 purging all the gas out out and you are getting 100% CO2 or a mixture?

Probably the same with propane. Some people will loosen the screw to the tank valve to release the gases when filling up the tank and some do not, even at the same store.

I'm not going to worry about pruging kegs until I get a conical or start canning beer.