Fermenting in keg?

[TheMattTrain]

Last weekend I had to move a beer out of a carboy and into a keg because I needed the carboy for another beer I was brewing that day. I also had noticed a small film on top of the beer which I've noticed on some of my beers before but they never turn out to be infected. I think it's from the StarSan, but I don't know for sure. The beer had been fermenting for 3 weeks so it should have been ready but it was about 15 points off. It was fermenting on the cold end of the yeast, so it's possible that it went dormant and never finished.

I decided to purge the keg and then let it sit outside of my fridge until I was ready for it. It's an Irish Red Ale so I'm not planning to start drinking it for a few more weeks. I want to have some for St. Patty's Day.

When I checked on the keg this morning, I pulled the vent to see if there was pressure in the keg. There was. It vented. It would seem to me that if there was no fermentation going on inside the keg that I wouldn't get any release of CO2 when I pulled the vent. Any pressure I had in there from when I purged it last weekend would have dissolved into the beer.

I had to run home quickly a little earlier today and I pulled the vent again to see what would happen. More pressure relief.

I know there's no way to be sure without checking the gravity, but would it be fair to assume that this beer is fermenting again? I'd take a gravity sample, but I don't want to open the keg if I don't have to. I also don't want to draw a sample out of a picnic tap for fear of pulling any yeast out that it might need to finish up.

Thoughts? Opinions?

 

[Double_D]

It could be off gassing dissolved Co2 also. The only way to know for sure is a gravity reading.

The thing about removing yeast is if it's at the bottom, it's already floculated. Active fermentation is in my understanding conducted by yeast still in suspension

 

[johngaltsmotor]

You can confidently draw off a small sample to measure FG. Any yeast that are settled on the bottom are basically dead and not actively fermenting, the ones that are still working are floating around eating sugars, not waiting for the sugars to fall to them.