While it can be tempting to view this as a relatively benign issue that will have no immediate impact on your home and health, we disagree. The stack effect is most commonly seen in homes that already have vulnerabilities or damage, but it can also have an impact of its own.    The Stack Effect is a Symptom    Even if you are not convinced that the stack effect is something to worry about on its own, you should be concerned as to how it is possible for it to take place within your home. While most properties have some kind of ventilation in the attic, the stack effect needs more than one entry/exit point. As such, the sudden onset of the stack effect should be a concern for you.    The sudden onset of this issue in a home where it has not always been present is an indicator of some kind of damage to the property. This is usually in the crawl space or lowest level of a home. The most common cause will be a non-encapsulated crawl space or uncovered crawl space vents, but there are other potential issues that could be at work.    The Stack Effect can be Dangerous    Because of the way the stack effect increases airflow through your home, it can be dangerous for several reasons. First, this airflow from outside can bring harmful allergens and contaminants into your home or contribute to the spread of things like mold and mildew. This can cause respiratory issues and skin irritation, among other things.    One of the most pressing issues, however, is the way that this can accelerate the spread of immediately harmful substances like gas. If you have a gas or carbon monoxide leak in your home, this kind of airflow will make it spread through your full home with alarming speed. Fire will also spread incredibly quickly when the stack effect is at work.