Final answer:
The rapid increase in intensity of a ventilation-limited fire is often caused by unventilated or improperly adjusted heating sources leading to oxygen-deprived environments that facilitate intense combustion.
Step-by-step explanation:
A common cause in the rapid increase of intensity of a ventilation-limited fire involves situations where there is insufficient oxygen for combustion due to unventilated or improperly adjusted heating sources, such as gas or kerosene heaters. When the area is decreased, this can also increase the intensity of a fire, as seen with the concentration of sunlight capable of igniting materials. Conditions such as wind-driven fires on uphill terrains can also lead to more intense flames, creating hazardous situations where fire spreads quickly, and escape routes are compromised, as historically seen in tragedies like factory fires with locked doors.