An atom is a nucleus containing positive protons orbited by negative electrons. With an equal numbers of protons and electrons, atoms do not carry an electrical charge. Negative ions are molecules that have gained an electron. They are created in nature by rain or waterfalls, lightning, trees, seashores and other natural sources. Negative ions are believed to have a greater effect on people than corresponding positive ions. The depletion of negative ions in polluted areas and most indoor environments is the reason for the development of negative ion generators to help people.
Negative ions are believed to increase levels of the chemical neurotransmitter serotonin and increase oxygen flow to the brain, thus alleviating depression, providing stress relief and boosting energy and alertness. Columbia University professors Michael Terman and Jiuan Su Terman have conducted controlled studies of negative ion generators on people suffering from seasonal affective disorder, or SAD. Their studies have shown between 42 and 58 percent of people report significant benefits from the negative ion generators. A 2006 Columbia study showed that sitting in front of an ionizer emitting negative ions at a high rate was as effective at relieving SAD symptoms as sitting in front of a light box for the same amount of time. The treatments were used for 30 minutes daily.
Negative ion generators utilize electronic devices which cause an electron to be added to oxygen molecules and trace gasses. The resulting negative ions not only are theorized to enhance mood and alertness, but to act as air cleaners as well. They transfer negative charges to particulates including dust, mold, pollen, animal dander, cigarette smoke, bacteria and more, which then attract positively charged ions. Eventually the particles become heavy enough to drop from the air to the floor and other surfaces, where they are cleaned up by dusting, mopping or vacuuming. Some negative ion generators are designed to attract the positive ions on a bar in the machine, and so require regular cleaning.
Lack of Research
The United States Food and Drug Administration has not approved negative ion generators as air purifiers, apparently due to a lack of scientific research. In 2003, Consumer Reports magazine stated that nearly all air ionizers receive a "fail" rating when compared to conventional high-efficiency particulate air filters, commonly called HEPA filters. A study published in the 1991 Journal of Occupational Medicine found no effects from negative ion generators on ion levels, airborne particulates or reported symptoms when the ionizers were used in two office buildings over two five-week periods.