Still actively fermenting?

I know its the best way to confirm if something is done fermenting is to take gravity samples on consecutive days. That being said I've got an extract iipa that has been fermenting for about two weeks now and I'm still getting sporadic (a few bubbles maybe once an hour, if that often) activity from the blow off tube. I'm wondering if that is gas from the co2 blanket in the head space just creeping out the tube or a sign of active fermentation. I'm planning on transferring to a secondary to dry hop, but obviously don't want to be premature and unnecessarily open up my bucket to take a sample.

Thanks for all the help and sorry for any spelling issues, wrote this on my phone

You already answered your question, the only way to know if fermentation is done is to take a gravity sample a couple of days apart and if the number remains the same, chances are it is done. Those bubbles could be caused by just about anything.

As mentioned, you answered your own question. Hydrometer is the only way to know if activity is done.

I assume that if you know about hydro readings, then you also know not to equate airlock bubbles with fermentation, and how it could just as easily be bubbling because of a change in temp, barometric pressure, because the vacuum hit it, or traffic is going by. And that an airlock is a valve, not a fermentation gauge.