The Friedrich line of room air purifiers has been discontinued but I’ve added it here anyway in case someone was wondering why they couldn’t find one. –ACboy
Friedrich Air Purifier: C90B
Indoor air quality has become a major concern. This is due, not only to medical concerns for those vulnerable to allergens, but also because the general population has become more aware of indoor pollutants. The problem is made even more important as houses and buildings are better sealed to prevent heat/cold loss. Insulation prevents free air exchange and concentrates unwanted odors and particulates.
The issues of mold, microbial contamination and indoor air remediation have brought the topic into the professional realm. There are even courses offered in these areas for HVAC personnel.
The Friedrich air purifier C90B is a “filterless” unit, although it does have two filters. A pre-filter catches large particles (like dog hair or dust clumps) to protect the internal workings and a final, carbon filter at the outflow end helps reduce household odors. But the main action is the same as other electrostatic precipitators.1
Air moves through an electrostatic grating, and any particles in the air pick up a charge. The air almost immediately goes to the next step, where a charge of the opposite polarity then pulls the particles to another plate. The plates will pick up material from the air and have to be cleaned – weekly if the house has a lot of pollutants and monthly otherwise. They can be hand washed or run through the dishwasher.
Friedrich has all the advantages of this type of purifier. They are very inexpensive to run because the only power consumption is for the fan. They are quiet, again because the fan doesn’t have to be high powered to force air through the unit. They are also excellent at removing smoke and other very fine particles.2
Downside and discontinued
In 2008, Friedrich and other manufacturers were soundly criticized because electrostatic units were found to have some problems. The first was that the units produced some ozone, a gas that can cause problems with allergy sufferers. Although the level of ozone was very low, this was still a concern. A second, and just as powerful criticism, came because some units actually produced more pollutants than they removed.
To understand this latter criticism, it’s important to note that charging an airborne particle may cause a chemical reaction or a splitting of the particle into smaller pieces. In effect, there’s some unintended chemistry going on that can create new items – at least some of which escape the process and recirculate back into the environment.3 At the same time, Consumer Reports quit recommending this type of air purifier.4
These concerns, as well as at least one class action lawsuit, resulted in Friedrich withdrawing from the air purifier market. At their website they still sell the pre and post filters for the C90B, but other than a press release (2008), they do not mention the product at all.5
Friedrich air purifiers may still be available online and are still in service. However, for all intents and purposes, they are no longer being sold retail.
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