The ionizer (stage 11) of the Puritii Air Purification System produces negative ions, which help to clean the air by causing very small particles to become attracted to each other (forming bigger particles that will be filtered in the next circulation through the purifier) or to surfaces. People who have used the ionizer have reported better sleep, reduced stress and fatigue, and a better smell in the air.
Demonstrating that the ionizer is working can be done using an air ion counter. Several ion counters exist (usually very expensive), however they are not all reliable. The ion counter used for third-party testing of the Puritii Air Purification System is called AlphaLabs AIC (see the device on the left in the picture below). Some representatives have attempted to use the KT-401 Air Ion Counter (the handheld device on the right in the picture below, but it does not work well. So you don't need to go buy these expensive testers, we have done the test in our office and you can see the results in the pictures below: