If there is an improper balance of oxygen, what happens to flammable vapors?

When there is an improper balance of oxygen, flammable vapors may not ignite or burn effectively. Combustion requires an optimal mixture of fuel (the flammable vapor) and oxygen. If the oxygen concentration is too low, there won't be enough to support the chemical reaction necessary for ignition. This lack of sufficient oxygen inhibits the ability of the vapors to combust, leading to a scenario where they remain unignited, regardless of the presence of an ignition source.

In contrast, a high intensity burn would require an adequate amount of oxygen, and instantaneous explosions typically require specific conditions, including a rapid increase in pressure, which isn't necessarily influenced solely by oxygen levels. Lastly, flammable vapors becoming more reactive would imply that they could ignite more easily, which is contrary to the effects of insufficient oxygen. Thus, the correct understanding reflects that flammable vapors will not ignite or burn when the oxygen balance is improper.