Don't ask him about the break-up. It would just be adding fuel to the fire.
Don't ask her why she's acting that way. Clearly she wants attention, and you'd just be adding fuel to the fire.
When Meredith and Tom fight over silly things, he knows it's better to be quiet than to argue back and add fuel to the fire.
Shouting at a crying baby just adds fuel to the fire.
People are already unhappy, but if the government increases taxes, that'll just add fuel to the fire.
When someone loses their job, you shouldn't prod them for details about it. It just adds fuel to the fire.
Please don't talk to him when he's in a bad mood. It just adds fuel to the fire.
People were already upset with the government, but recent news about spying activity has only fueled the fire.