The most efficient air filter for improving air quality is the electronic air cleaner. Air returning to the furnace or air handler passes through a screen to trap any large dust particles or objects. Using line voltage to power circuitry, a positive electrical charge of high voltage (upwards of 12,000 volts) is sent through fine wires stretched across the air stream immediately behind the screen. The dust particles pick up a positive charge, then pass through plates or grids that are negatively charged. Opposites attract, and the dust particles collect on the plates. Smoke is microscopic particles, and is trapped as well. Ozone is created from the charged air, which helps kill bacteria and odors.
Electronic air cleaners will usually operate at 95% efficiency, allowing little or no dust to pass through. The dirtier they get, the lower the effectiveness, so clean grids are a must. Before removing the screens and grids for cleaning, it is imperative to shut the power off and wait a few seconds to allow the grids to lose the static charge. They are dishwasher safe as long as they fit inside. If not, sloshing around in a tub of hot soapy water will loosen dirt that can be blasted off with a garden hose. Extreme caution must be taken when handling to protect the grids and the person handling them. The plates are very sharp, and can cut like razor blades. The fine wires stretched across the grids are delicate and crucial to proper function. Proper spacing between the grids is important. Do not bend or distort them.
If the grids are not completely dry when installing them, do not turn the power back on; damage to the power pack can occur as the water will short the grids out. If in doubt about the dryness, leave the power switch off for a day or two; the air flow will take care of any residual water. Arrows one the grids will display the correct direction for air flow. Improper installation will render them useless. If the air cleaner was installed correctly in the return air duct by the original HVAC mechanic, air flow will be going from the duct toward the appliance. The arrows should do the same. Troubleshooting falls into two categories: Grid failure or power failure. Excess dirt or a large object stuck in the grids will cause an electrical short. A loud snapping noise will sometimes indicate this problem. If cleaning does not stop the snapping and the grids are bone dry, inspect the fine wires stretched across the terminals. If they are white from oxidation, gently run an old soft toothbrush up and down them once, then rinse and dry again.
Most electronic air cleaners have a light to show operating power. If the light is not on when the system is running and the switch is on, there are two possibilities. The power pack has burned out, the power to it has been disconnected, or the unit has a pressure switch to sense air flow and charge the grids and it has failed. Either repair means opening up the power pack, exposing dangerously high voltage. This task should be left to a qualified technician.