Final answer:
The stage where the visible flames diminish and the fire continues to produce smoke and toxic gases is called the smoldering stage.
Step-by-step explanation:
In the stage where the visible flames diminish and the fire continues to produce smoke and toxic gases, it is called the smoldering stage.
During this stage, the fire has an unlimited supply of fuel left over, which allows it to continue burning without visible flames.
Instead, it produces smoke and toxic gases such as carbon dioxide and water vapor.
An example of this stage is a campfire that has finished burning but is still producing smoke.