A muzzle loading black powder cannon is perfectly safe if used in the correct manner. 

 

Never stand in front of or foreward of the the cannon

 

Only use Black Powder NEVER use Gun Powder

 

Ensure the barrel is clean swabbing it after every use.

 

Never overload the cannon

 

Never aim the cannon at anyone or anything

 

Never force anything down the barrel

 

Keep your powder away from your cannon in a locked box lined with a fire retardent material