In indoor air quality discussions, I often hear these two perspectives:

1.) Why use an air purifier when you can just open a window (ventilation)?

2.) Don't open a window while an air purifier is running.

If you dig deeper than that, you encounter more opinions:

1.) Who needs fresh air when you can use activated carbon to adsorb VOCs/odors?

2.) Activated carbon doesn't really work to adsorb VOCs/odors. Use fresh air (ventilation) instead.

So who is right?