They have ventral lungs which, peculiarly and unlike other fish which may breathe air, are not derived from the swim bladder! They take in air through two spiracles, where it then enters the esophagus, through the glottis, into the right lung, where a separate opening may then allow the air into the left lung as well.
The way this sold was the best. Someone was browsing my stuff and said out loud “Oh my god is that a Bichir?!” And they were the proud owner of a Blue-chir after we nerded out about our fish. (If you’re reading this, Hi! I remember your Oscar!)
Why did this make me so happy? Because I too have gone, with all the fish nerd joy, “Oh my god is that a bichir?!” And basically bought it immediately, too.