Ionization systems and methods include moving air into contact with one or more ion generators and then past an ozone removal assembly to remove at least some ozone from the air. The air may be moved by a fan and may be filtered before contacting the one or more ion generators. The amount of one or more of the following of the air may be measured: the amount of ions, particulates, temperature, humidity, and other relevant factors. The ionization amount may be adjusted based on one or more of the measured amounts. The one or more ion generators and ozone removal assembly may be constructed as part of a single unit so they can be removed and replaced easily.