Question about airlock for primary

Good afternoon

Quick question... I've had an IPA in primary for exactly 3 weeks and I was going to dry hop it today before I bottle it next week. Do you think I need to keep an airlock on it after 3 weeks or can I put a cap on the carboy after I dry hop it?
I ask because I ordered a second carboy that was supposed to come with an extra 3-piece airlock but the company never sent the airlock and just sent a cap for the carboy instead.
Do you think there would be any risk in switching out the airlock for the cap so I can use the airlock for a new batch this weekend?
*For the record, it stopped bubbling about a week and a half or 2 weeks ago.

Thanks!

 

You need to have some way for the outgassing CO2 to escape. There will be some CO2 coming out of solution for quite a while after fermentation is over.

You can still use the second fermenter even though you don't have an airlock. Stretch a piece of Saran wrap over the carboy's opening and hold it in place with a rubber band. Use a pin or needle to poke a tiny hole in it. That will let the CO2 escape but the bacteria out as they can't swim through the escaping CO2. When you have the first beer bottled, you can use that airlock for the other carboy and the Saran wrap will be ready for the next batch.

 

Yeah I was thinking I would still need it. Thank you for the advice with the saran wrap! Might be good enough until a new airlock arrives.