Sending Airtable data to Firebase (and sending data in the reverse direction) can be done quickly with Bracket. You just have to input your Airtable API key and connect it to your Firebase. It handles syncs in just either direction, or both at the same time.
There's also features that you can customize. If you only want to sync certain fields in two directions and make other fields read-only in Airtable, or if you want to write queries to make the data you pull into Airtable very customizable, then that's all possible!