Why? You'd think folks would realize what could be the possible damage to the drive train while purposely causing fire to erupt from the exhaust? To me, it is about as inane as doing donuts in the middle of Hollywood and Vine. As Forest Gump would say... "Stupid is as stupid does!"
I believe these items were conceived and created to attract attention. With some customers catching their vehicles on fire (see YouTube), they are great at delivering that experience.
I attempted to get an Material Safety Data Sheet (MSDS) for the chemicals involved, but Dragonbreath does not have them listed on-line.
"Your car must shoot flames out of the exhaust tips before purchase." (Dragonsbreath faqs page). There's a solution for that, below.
What I'm most interested in is how long any of these companies will last. The test, acceptance and safety information for different products, different vehicles, states and municipalities? If I attempted to create a company like this, I'd be run out of business before the ink was dry on the business card.