All of the CF filaments now say to dry before using. My X1C came with a 1/4 roll of PAHT-CF and i did not dry out when i first opened it and put it in the AMS (it’s still in there).
Once i open the PETG-CF and PLA-CF, do i really need to dry them before use them? Or can the get damp in the vacuum sealed bag?
Anything is possible which is why they suggested drying first. I have not dried any of the Bambu filament I have gotten yet, including the PLA-CF and PETG-CF. It has all printed well out of the package.
A lot of this depends on where you live, what the local climate is like, and where you store open filament. The ambient temperature and humidity will be a lot different for someone who lives in in a hot/dry climate compared to someone who lives near large bodies of water.
Brand new, freshly opened, high quality filament that goes straight into the AMS is probably good without drying. Stuff that got opened and left out overnight in your mom’s basement during rainy season should probably be dried out. Certain filaments will soak up quite a bit of moisture pretty quickly in the right conditions.
I feel like a lot of the warnings about drying new filament is just to simplify things, because there are so many variables. But then again, I’ve had two recent Bambu Lab filament bags come unsealed on their own in the last two weeks, so I’ll probably stick them in the oven before I used them. When in doubt, dry it out.
Thanks for the replies! 
I have a Creality dryer which displays the RH of filament.
Just bought some from Amazon, (Eryone) took it out of the vacuum sealed bag and put it in the dryer! I immediately got an RH of 40%. Surely that is very high for new filament? PLA.
What did the RH display show before you added filament and turned the dryer on?
Remember that the display shows the humidity of the AIR inside the dryer. It takes a little time for most hygrometers to adjust to changing humidity, so “immediately” seeing 40% may just have reflected the moisture in your environment.
I’m not familiar with the Creality dryers, but many dryers do not vent moist air outside of the dryer, so when the heat drives moisture out of the filament it has no place to go except the air inside. It is pretty common for this type of dryer to show increasing humidity as temperature rises, enough sometimes to cause condensation. You can help such dryers by opening them a bit to let air circulate.
If you wish to be sure your filament is dry, weigh the spool, dry it, weigh it again, repeat until the weight stops dropping. 95% of the spools I’ve bought had at least 3 grams of water, some had as many as 8 grams.
Mmmmm I see what you mean!
I have now switched on the dryer for 30 mins to give it time to settle down!
RH was 28%.
I put in another new freshly opened spool and RH went up to 32%.
The dryer is vented.
It has provision for using a ptfe tube and printing while drying so can vent through that. I have never seen any moisture/steaming up.
Looks as though it is a scales job then!