|MadSci Network: Engineering|
Just testing to see if the appliance puts out ionized air is one thing. Judging the amount produced is likely to be a bit more difficult, if not impossible, with simple tools. I don’t have one of these ionizers at hand to test but what I’m about to suggest should work. One of the simplest devices with which to check for charged particles is the electroscope. You can find directions for building one of these many places on the web or in the Boy Scout “Atomic Energy” Merit Badge book. It is basically two thin pieces of metal foil hanging from a conductor attached to a metal top, often the lid of a jar. Letting the negatively charged air from one of these air ionizing machines blow over the top should cause the leaves to separate as the charge is collected. One could also first charge the electroscope positively by touching its top to a piece of cloth that has just been used to charge a rubber balloon. The balloon charges negatively so the cloth is left positive. You know the balloon is well charged if it will stick to the wall or ceiling. Note these sorts of tests really only work well on days with low humidity. A positively charged electroscope should have the leaves more rapidly fall back together as negatively charged air is blown across its top than if left alone. You do not blow the air directly over the leaves just the top of the closed electroscope. In principle one could time the rate at which the leaves fall back together to judge which machine was producing the most ionization. This could be complicated by having different rates of air flow from the different machines as well as the distance from the machines. Perhaps the best way to get a good comparison done with proper instrumentation would be to check out the “Consumer Reports” web site. They also noted about a year ago that some of these devices actually put out too much ozone (which can be a lung irritant) as a byproduct of negative ion production.
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