Technology Review, Jan 1983 v86 p74(1).
Negative ion generators are curious little devices--their manufacturers' claims are inevitably followed by exclamation marks. "Is your air healthy?" asks one ad. "Recreate fresh mountain quality air indoors!" Negative ions, say manufacturers, make you feel alive, revitalized, and alert while relieving depression, headaches, and allergies. Trillions of these incredible negative ions somehow are supposed to kill bacteria and make plants grow better.
But do such claims have any scientific basis?
Possibly. First, it is true that the number of "small ions" in the air --electrically charged molecules and atoms that are highly mobile-- varies widely. Clean outdoor air may have 1,000 positive and 1,000 negative ions in each cubic centimeter, while polluted city air probably has fewer, and air- conditioned offices may have only 100.
Commercial ion generators can indeed change indoor ion levels drastically. When a high negative voltage is sent into a needle point, it generates both positive and [sic] negative ions. The negative ions are repelled by the negative needle (like electric charges repel) and blown into the room by a fan. The physics of ion measurements are almost certainly more complex than manufacturers and some experimenters recognize. However, an efficient ion generator may bring a room to even higher negative ion levels than typically found outdoors.
The question is whether increasing the number of negative ions makes people feel more comfortable and work more efficiently. The answer is especially important in regard to the video screens that display words and numbers at computer terminals. These screens, which many users say cause fatigue and headaches, usually have positive voltages strong enough to wipe out nearby negative ions.
L. H. Hawkins, from the Human Biology and Health Department of the University of Surrey in England, has performed two sets of experiments to find out how negative ions affect people. In the first set, Hawkins maintained high levels of negative ions in a room part of the time, but maintained predominately positive ions in the room the rest of the time. The people in the room, unaware that the ions were being manipulated, performed standard tasks.
When the ions were negative, the subjects did 25 percent better at complicated tasks such as drawing something while looking at its reverse image in a mirror. There was a smaller but statistically significant 6 percent improvement in simpler tests such as reaction time. Women seemed more sensitive to ions than men, and high humidity and temperature tended to wash out the benefit of negative ions.
In a second test, Hawkins installed two commercial ion generators in a congested computer office. The fans on these generators could be switched on separately from the ionizers, and with the fans always running, nobody in the office knew whether the ionizer was working. According to Hawkins' measurements, with the ionizer on, the office had about 3,500 negative and 100 positive ions per cubic centimeter of air; with it off there were about 550 negative and 500 positive ions.
At the end of their shifts, the 54 people in the office filled out questionnaires about how they felt and how they rated their environment. Negative ions did seem to produce positive effects. Workers complained of headaches in only 6 percent of the shifts when the ionizer was operating, but they complained in 26 percent of the shifts when it was off. The questionnaires revealed similar increases in how pleasant workers felt and decreases in complaints about nausea and dizziness.
Since some workers in computerized offices stay at terminals near video screens all day, where negative ions are so depleted, ionizers could be helpful accessories. But Hawkins emphasized that his findings are tentative. Negative ions are chemically reactive, so they could have some damaging effects. And other factors will undoubtedly prove far more important for workers, such as how satisfying the work itself is or what the boss is like.
Negative ions and positive vibes.
Work environment - Physiological aspects
Anions - Physiological aspects
Technology Review, Jan 1983 v86 p74(1).
Full Text COPYRIGHT 1983 Massachusetts Institute of Technology Alumni Association