Friedrich C90b Air Purifier Review

C90B air purifiers: $599.00

Replacement Carbon Filter: $34.95

Replacement Nylon Pre-filter: $39.50

The Friedrich air purifier, now called Friedrich "C90B", is a top quality electrostatic air cleaner producing outstanding airborne particle removal.

The downsides are intensive maintenance of the plate filters and ozone emissions, plus an industrial aesthetic which puts many off.

The Friedrich C90B air purifiers are an upgrade of the C-90A.

The "B" has been available since July 2005, but was not marketed real aggressively since many dealers still had commitments and unsold inventory in the C90A.

friedrich air purifier

With improved clean air delivery rates (CADR) and larger room size spec, the new Friedrich air purifier is 15% more powerful than C90A.

CADR's of 384 dust, 326 tobacco smoke, 421 pollen, and room size 506 square feet, push the C90B Friedrich air cleaner very close to its main competitor, the Blueair 503 air purifiers (375 dust, 375 smoke, 375 pollen).

Consumer Reports liked the old C90A Friedrich air purifiers, ranking them number one: the new model should fare even better in their short tests.

Popularity peaked shortly after the 2005 boost from Consumer reports. In 2007 CR blasted ozone emitting "ionizers," then somebody noticed that they had promoted the ozone prone C90.


The C90's still have a following, many people love 'em, especially in dusty work environments.

Twenty six reviews at average 4 of 5 stars.

Thirteen reviews at average 4 of 5.

A four step filtering process is claimed to remove particles beyond HEPA spec (99.97% at .3 micron) to 0.01 micron.

This is very good performance!

When the electrostatic collector plate is kept clean, it continues at this level.

Most users of electronic air purifiers will not maintain clean plates, despite good intentions at purchase.

There are a few carbon mesh air filter replacements to run up costs, but the C90B Friedrich purifiers cost of ownership is lower than many lower priced HEPA air purifiers.

With all electrostatic air cleaners, the buyer is trading their labor (frequent plate washing) for the cost of filters.

The C90B is not mechanically complex; a washable pre-filter lies ahead of dual Honeywell-made de-ionizers and a large precipitator grid, plus a final carbon impregnated post filter.

Air comes straight in the rear and out the front through large black grillworks.

A high voltage DC power supply runs a powerful three speed fan in the middle of a heavy duty molded plastic body.

Call the Friedrich air purifiers "utilitarian." No frills, no electronics, just military-like function.

So what's wrong with that?

I thought you'd never ask.

Frequent Purifier Plate Cleaning

In high-particle rooms, especially where tarry tobacco smoke is present, efficiency of the electrostatic cell will degrade rapidly, requiring very frequent plate washing.

If washing is neglected, as is extremely common, all electrostatic purifiers will bypass lots of finer particles just like a cheap, leaky HEPA air filter.

These fines accumulate inside the exhaust housing, on the fan, and in other less accessible parts of the machine.

To maintain efficiency, wash plates every 3 days.

In fairness to the manufacturer, their Friedrich C90B literature is very detailed concerning the need for frequent careful washing.

And many a HEPA air purifier is out there with dirty filters running way beyond replacement intervals, bypassing fine particles like crazy.

Cleaning the electronic cell is easy if it fits in your dishwasher.

Compare the space inside your dishwasher to the dimensions of the electronic cell: 16" high x 12 1/2" wide x 4 1/2" deep.

"Just put it in the dishwasher."

If it doesn't fit, the user's manual includes extensive instructions for a lengthy cleaning process involving soaking and rinsing in very hot water.

This same problem haunts almost every electrostatic air purifier, Friedrich C90B is no exception. Some smaller air cleaner's plates will be easier to fit in the dishwasher.

Care must be taken to avoid cuts from the sharp, fragile plates, which cost $160 to replace.

The ionizer wires may get dirty: occasional cleaning is recommended. I have seen complaints about the life expectancy of delicate ionizer wires and collector plates with frequent washing.

The point here is for consumers, adverse to HEPA filter changing, to avoid being mislead by illusions of zero maintenance.

When the carbon post-filter gets dirty, it can be vacuumed, but this will not restore odor removal capability. This filter must be installed for the machine to run.


The complete Air-Purifier-Power noise specification (sound in decibels @ air volume in cubic feet per minute) is;

55dB(A)@410cfm on high, awesome!

50dB(A)@340cfm on medium,

40dB(A)@280cfm on low.

For those new to this site: noise is relative, not just how loud, but how much air purifying is done?

Like most air purifiers, the C-90B is loud on high speed. But 410cfm(!) is lots and lots of purified air.

And 40dB(A) on low is not real quiet for sleep, but at that lowest setting it moves more air than almost every HEPA air purifier on high. 280 cfm is lots of purified air, real air purification power!

Freidrich C90B makes crackling sounds, which worsen if the air purifier's plates are not kept clean.

Some users report minor, but irritating, vibrations of the housing. Others report out of balance fans hitting the housing.

Airflow into the intake and from the discharge grilles must not be blocked. This just about means the air purifier must be placed sideways along the wall.

The rear of Friedrich C90B looks just like the front, a black grille. The required eight inch wall clearance would have the cleaner sticking out pretty far if installed at a right angle.

Drafts could be a problem with a bedroom installation. On low, the large front discharge area makes for gentle airflow

Weighing 28 pounds and measuring 19" by 15" by 21.5", the C90 is large, and boxy.

C90B's heavy duty, almost military appearance, is quite a contrast to the current crop of stylish, ineffective "tower" air purifier models.

C-90 Purifiers Ozone

Ozone(O3) is produced at "safe levels" as a by-product of air ionization and the smell may be quite noticeable. Friedrich C90B produces .014 parts per million (ppm) of O3, well below the FDA limit of .050 ppm for medical devices.

Many customers have returned units, complaining of an annoying odor emitted by the unit, probably ozone. The smell lasts about an hour after the purifier is turned off, but O3 will persist much longer.

Air-Purifiers-America rated C90 only 3 stars due to the ozone smell and higher than average product returns. Some people get headaches around even low levels of ozone.

I rant at length elsewhere on this site about the dangers of ozone. Due to these emissions, I do not recommend this product for allergies, asthma, or MCS.

Does it do VOC?

These purifiers do a very good job at removing allergens and dust.

Unfortunately, the Friedrich is less effective with odors and gaseous chemicals.

When plates are rigorously cleaned, it will purify the air of many side stream smoke particles, but not the invisible gases which accompany them. No air purification system has been created that can fully protect against secondhand smoke.

Although the Friedrich has a carbon post-filter, it does not have sufficient carbon for major VOC or heavy odor removal.

Some user reviews have reported satisfactory removal of light odors with fresh filters.

The ozone byproduct is a potent odor oxidizer, probably removing more VOC and odor than the carbon filter.

There has been some price creep on the carbon filter. Three to six months is the typical replacement interval.

Going toward the short side for best odor removal could result in $100 annual filter costs.


The high voltage used in the ionizer may create significant electromagnetic fields.

Multiple users report TV (Radio Frequency) RF interference up to 20 feet from the C90.

The “90” in Friedrich C90B refers to the 90 watt energy use on high, which is pretty frugal for an air purifier this strong.

A one year warranty is on the short side. Friedrich is a San Antonio based air conditioning company.

I have seen a couple Friedrich workshop air cleaner installations, the machine fits right in; heavy duty construction and appearance, fast, efficient particle removal.

In a workshop air cleaner, the need for fast toxic particle removal outweighs the ozone problem.

I have a "77" (good) rating on the Friedrich C90B due to ozone emissions and lack of VOC gas capability.

Compare the upper end Blueairs.

Some dislike the shrill pitch of the Blueairs: Friedrich C90B is fairly quiet, and very strong, on low.

Friedrich C90B Air-Purifier-Power Rating: 77 "good"

Each of ten factors gets up to 10 points, 100 is perfect and very unlikely.

1. First do no harm; minimal out gassing, no ozone.

Score: 6 of 10, .014 ppm O3 is low, but not "safe".

2. Serious gas and odor removal is a requirement if health benefits are expected: Units with real carbon VOC capability rank higher.

Score: 5 of 10

3. Quality construction; case, gaskets, seals, and precision fitting eliminate air bypassing and assure high efficiency at filtering sub-micron particles.

Score: 9 of 10, excellent filters when cleaned.

4. The design maximizes the lifespan of each filter stage by allowing independent filter replacement. Ideally this is combined with electronic monitoring of filters.

Score: 8 of 10

5. Unit has long life filters, low maintenance requirements, and reasonable operating costs.

Score: 8 of 10, I don’t agree with the “low maintenance” label for electrostatic purifiers.

6. Purifier produces low noise levels and meaningful air flow rates relative to noise.

Score: 10 of 10, a bit loud on high, but real airflow to match.

7. Manufacturer has a track record, with many units in the field and a reputation for supporting what they sell. Warranty period and average service life are long.

Score: 8 of 10, one year warranty too short for price range.

8. Purifier is a value in terms of price/performance ratio. Every price range should be included, “models above $1,200 are best”, while true, is not useful to most consumers.

Score: 7 of 10, costs as much as Blueair 501.

9. No dirt; air cleaners and manufacturer should be devoid of class-action suits, high returns, recalls, consumer complaints, and legitimate negative consumer reviews.

Score: 9 of 10, some vendors report returns.

10. Unit is stylish, portable, comfortable, and convenientfor consumer use.

Score: 7 of 10, boxy, no electronics

Air-Purifier-Power Numeric Rating; 77, Good for Smokers and shops.

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