Zojirushi: Ballad of a Thin Man

The Zojirushis are AHAM certified with clean air delivery rates (CADR) of 94 dust, 94 smoke, 107 pollen,and room size 146 square feet.

Like many European purifiers, the slim Zojirushi air purifier's airflow is quoted in cubic meters per minute: 3.1 m3/min.

Applying a handy conversion factor known only to international air cleaner aficionados like you and me (35.3145 cu. ft./cu. m), we get 109 cubic feet per minute (CFM).

This is very consistent with the CADRs cited.

This is a pretty weak air cleaner, a room size consistent with power would be 110 square feet, a small bedroom.

Did You Say HEPA-type?

Zojirushi MTC14 air purifiers have no prefilters, exposing the 2 side-by-side HEPA-type filters directly to the airstream.Yes you read correctly, HEPA-type filters, not "true-HEPA" or “99.97% at .3 microns HEPA” as misstated on some vendor's websites.

A HEPA-type filter meets nobody’s specifications, it is whatever a vendor wants it to be.

In-My-Exceedingly-Humble-Opinion, these "type" filters belong only on $50 and under discount department store air cleaners.

Zojirushi may have deliberately under-filtered their air purifying product to keep fan power down and profile slim.

True HEPA air purifiers need powerful, noisy fans to pull air through tightly built and sealed filters.

While the design specs are achieved, the PA-MTC14 is both quiet and slim, I expect the efficiency of this arrangement to be below par.

Notice the significant difference in the Zojirushi air cleaner's CADRs for dust and pollen.

As stated elsewhere on this site, CADR testing uses particles ranging from .9 micron to 11 micron to simulate dust and pollen. Real world pollen, ranging from 5.0 to 50 microns, is among the largest particles captured by air filtration.

Because of this large particle size, seasonal allergy to airborne pollens is among the easiest to cure with air purifiers.

Poorer performance on the smaller particles suggests inadequate filtering of the real dangerous .1 to .3 micron particles that premium true-HEPA air purifiers strive to eliminate.

What I am concerned here with is bypassing, allowing particles to slip through and past the filter.

Filters are projected to last up to 2 years under normal operating conditions, but the user's manual lists numerous exceptions.

In smoking, pet hair, or dusty environments, filter life will be much shorter, due to the absence of a cleanable pre-filter.

Behind the particle filters, two carbon impregnated odor filters precede the fan. These are not heavy carbon and also are unlikely to adsorb chemicals or odors beyond a year or so.

Replacement filter kit part number PA-FMC02, $48.00, includes 2 HEPA-type and 2 carbon impregnated filters.

At least the replacement filter kit is cheap. Based on a 1 year replacement intervals a filter cost to initial purchase price ratio comes out to about 3. This is above the industry average for filter economy.

I found few vendors stocking these filter kits, which are available on the manufacturer's website.

Zojirushi is Partially Automated

An odor sensor provides automatic operation, turning up the fan when airborne impurities are detected.

This sensor has two levels: normal and gentle. This may explain the Amazon user review which complains of seemingly arbitrary activation in auto mode.

Switch to "gentle" mode, this may help.

I rant elsewhere about the desirability of sensor driven automatic air purification, but here ZO has omitted a key component, the particle sensor.

Without the ability to respond to particle levels, automatic operation is limited.

Particles, stirred up by feet across carpet, air conditioning drafts, or even making the bed, are an ever present episodic air pollutant.

Sharp made this same mistake with their FPN40CX, but corrected it in the Canadian sequel, FPR45CX.

The Air Quality Monitor displays detected odor levels.

A filter replacement indicator is a timer, not a sensor.

The shut-off timer allows 1, 2 or 4 hour delayed turn-off. If the air purifier is left running for 36 hours without user input, it shuts down. A remote control is included.

Quiet Air Cleaning

Airflow for the lower two speeds is a prorated estimate based on energy draw.

While this is quieter than many real HEPA purifiers, this machine does not have the power to make lots of noise.

Compare Sharp FPN60CX; 40 dB(A)@212 cfm, twice the power, less noise.

With energy use on each of 3 speeds at 20/33/55 Watts, the Zojirushis are below the 2.0 dust CADR/Watt needed to get EPA Energy Star Rated. Slim and stylish at 19.6" x 5.1" x 18.1", and weighing 15 pounds, this air purifier is portable up stairs.

Warranty and Customer Service

Zojirushi Corporation is Osaka, Japan-based, and warrants the purifier for one year.

Some bread maker customers have complained of poor customer service.My calls to sales and customer service, based in Cupertino, CA, were answered promptly by friendly personnel without foreign accents. Of course, I wasn't trying to return product.

21 service contractors in the lower 48 are authorized to repair the ZO air cleaners.Many stateside vendors show web screens without inventory, only one Canadian vendor still offers this unit.Others appear to be drop-shipping from the manufacturer, citing 3 week delivery times.

Replacement filter kits (PA-FMC02) are also scarce.

One web vendor states: "We do not allow returns or cancellations for this manufacturer."

Conclusions

All this adds up to a weak review for the Zojirushi Air Purifier.

I think this is a good faith effort by a corporate engineering group without depth inindoor air.

Who would develop a HEPA-type product in the near $200 price class?

Even at the lower end of the price range I found advertised ($149.95), this air purifier is overpriced.

Other Asian builders have made similar mistakes.

Despite Zojirushis good quality and fair customer service reputation, I expect a thinning market and soft prices for the Zojirushi UltraSlim Air Purifiers.

Air-Purifier-Power Rating Criteria

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: 9 of 10.

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

Score: 7 of 10, little odor removal and very little chemical removal.

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

Score: 5 of 10, forget HEPA-type anything, anywhere!

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

Score: 7 of 10, lack of prefilter makes filter life claims suspect.

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

Score: 8 of 10, maintenance costs good.

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

Score: 8 of 10, quiet but weak.

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: 6 of 10, 1-year warranty should be longer, mfr lacks air purifying experience.

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: 6 of 10, overpriced.

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

Score: 8 of 10, manufacturer not air quality specific

10. Unit is stylish, portable, comfortable, and convenient for consumer use.

Score: 9 of 10, handy remote, partly automated interface.

Air-Purifier-Power Numeric Rating; 73