Which of the following is a warning sign of backdraft?

The presence of dense gray-yellow smoke, along with pressurized smoke exiting openings, is a strong indicator of a potential backdraft. In situations where there is a fire confined to a space, the combustion gases within can become heated and filled with unburned fuel. This creates a critical scenario where smoke is under pressure, and when ignited, it can lead to an explosive reaction.

The dense gray-yellow smoke typically indicates incomplete combustion, suggesting that there may still be flammable gases present. When this smoke is seen being forced from openings, it signifies that there are pockets of heated gas building up, which can ignite upon introduction to fresh oxygen. This state is characteristic of an impending backdraft situation, making it crucial for firefighters to recognize these signs to take appropriate safety measures before engaging in firefighting operations.