I think most have heard the advise that you should put flour (or baking soda) on a grease fire to absorb the oil before. While this is certainly better than using water, I'm skeptical.
For starters it is know that flour is excellent at demolishing flour mills, but in these instances it is a dust explosion (actually a deflagration) in a confined space versus a splash of mostly unaerated powder onto a fire. Even the fine particles that fall off should only cause mild flames compared to the on going grease fire. The main cause of skepticism is the potential charring of the flour releasing water and causing splattering (i.e. bigger fire).
Alternatively baking soda has been suggested, but this also seems dodgy as it starts to decompose at 50 °C releasing carbon dioxide and water, and how many people have enough baking soda to fill a pan in their kitchen ready to go? It seems that a lid would be the most appropriate response and of course would not recommend someone to do their own fire fighting if not prepared to do so, but when seconds count help is only minutes away.
I suppose that decomposition would be less of an issue if sufficiently slow kinetically. But debating physical sciences is a fools errand so I ask: Is flour or baking soda really suitable for extinguishing grease fires?