Most authorities on the subject agree that ions act on our capacity to absorb and utilize oxygen.  Negative ions in the bloodstream accelerate the delivery of oxygen to our cells and tissues, whereas positive ions slow down this delivery of oxygen, producing symptoms markedly like those in anoxia (or oxygen starvation).

The body chemical serotonin, linked with mood and stress, is also influenced by air ion levels. Too many positive ions alter the levels, causing stress and discomfort.  Increasing the negative ion concentration helps bring relief.

Researchers believe that negative ions may stimulate the reticulo-endothelial system, a group of defense cells in our bodies which marshal our resistance to disease.

Offices and organizations that have installed negative air ionization equipment have found that their employees are less likely to get colds, report absent less frequently and are generally more cheerful and alert.

Scientists have also recommended the use of negative air ionizers in the closed and artificial atmospheres of submarines and spacecraft.

Our modern vehicles have their problems too!  Basically they are a plastic-lined metal shell, with air supplied through ducting. All these factors dramatically increase positive ions.  Opening a window can cause problems, letting in polluted city air.

Many drivers, (long-distance drivers particularly) find using an ionizer in their vehicle helps their alertness and concentration - and in some cases, their passenger's travel sickness - along with the usual benefits of removing pollen and smoke.