UNFORTUNATLY I DON'T OWN THIS ITEM AND ONLY KNOW WHAT WAS WRITTEN ABOUT IT. I SUSPECT THE MECHANISM IS COCKED WHEN YOU OPEN AND LOAD AND THEN CLOSE THE BREECH. THE CENTER OF THE KNOB ON THE HANDLE HAS WHAT APPEARS TO BE A CENTER HOLE. PERHAPS YOU TURN THE KNOB TO OPEN AND THEN BLOW INTO IT AS DESCRIBED PROPELLING A STRIKER TO TRIP THE FIRING PIN.

JUST GUESSING HERE AS THE INFORMATION WAS NOT COMPREHENSIVE OR CLEAR AND I HAD NO WAY TO CHECK IT OUT.
I DO ASSUME IT WAS ACTUALLY TRIGGERED BY BLOWING AS IT WAS SPECIFICALY MENTIONED THAT IT WAS DESIGNED TO PROTECT THE MOUTH WHEN IT WAS FIRED.