GermGuardian AC4100 Review

AC4100 Air Purifier Review

Ohio-based Guardian Technologies Inc., founded in 2005 by two former Dirt Devil employees, has grown steadily despite the decade long flat spot in the air purifier business.

Guardian specializes in inexpensive UV-C germicidal air purifiers and sterilizers.

A recent new product is the GermGuardian AC4100 Table Top UV-C air cleaner, selling for just $56.

Now fifty bucks generally does NOT buy much air purifier, and AC4100 carries just a couple technologies, but it is a good value bundle for those who do not insist on being mislead.

Key technologies are "hepa," carbon, and photocatalytic ( PCO ).

Notice that hepa is NOT capitalized.

There are NO sensors or automation modes.

Competitors are few, most sell for at least double the price or have visible deficits.

I'd put this machine above the many small Honeywells and Holmes - department store air cleaners - in the big box aisles.

Professional reviews of air purifiers under $100 are rare, but has 64 customer reviews with a mean value of 4.2 stars. AC4100 purifier

One and two stars total 10% of the whole, acceptable for this price class.

Out of 64, only two were "one-star," unusual at fifty bucks.

"CADR" is an acronym for Clean Air Delivery Rate, a performance standard promulgated by the American Home Appliance Manufacturers Assn (AHAM), an industry lobbying group.

CADR is designed to support high-throughput department store purifiers which focus on macro particulates (mold spores, pollens...) and punish allergy shop machines which tend to target a smaller range of particles and chemicals (viruses, aldehydes...).

AHAM charges a pretty good price for their marketing service, and most will contrive not to subscribe.

It is increasingly common for CADRs to be quoted when no CADRs are listed at AHAM.

So we see CADR 58 Smoke, 64 Pollen for the AC4100, but these are NOT listed at AHAM.

Likewise, "up to 200 sq. ft." maximum room size is bandied about.

Here is the key to success with a $50 air cleaner - install GermGuardian AC4100 in an absolute maximum of 60 sq. feet.

Now that Pollen CADR is very good at identifying the best machines for seasonal pollen allergy, because seasonal pollens are relatively large and many cheap high CADR particle getters will suppress symptoms.

FLT4100 Filter Train

AC4100 has a simple filter train, a charcoal pre filter, a "hepa" filter, UV lamp and photocatalytic screen (PCO).

All these, except the PCO screen, must be replaced, maybe twice per year - a cash cow for Guardian.

The prefilter is NOT washable, but can be lightly vacuumed.

Here is the rub - HEPA?

Vendor sites say "HEPA Filter captures 99% of airborne particles, as small as .7 microns," (NOT HEPA) while Guardian site says both "99.97 % of .3 micron" (true-HEPA) and 99% at .7 micron.

So we are attempting to value the replacement filter/UV lamp costs but cannot determine what is actually for sale.

User reviews imply that substantial fine particle bypassing occurs in the Guardian AC4100.

If the filter is not snugly affixed (sealed) to the chassis, dirt will accumulate inside, ready to spray out.

A common practice is to make a true-HEPA filter but leave gaps so air can bypass it.

I would be very surprised to find the AC4100 true-HEPA and sealed.

Guardian has recently added a Replacement Filter Indicator and UV bulb warning lamp to the AC4100.

Of course, these are mere timers.

Replacement Filter E, Model FLT4100, is $15 below, but will double the minute something starts to go wrong.

AC4100 Photocat (PCO) ?

So the minor carbon in the pre-filter is just a fraction of 4100's gas pollutant odor filtration capability.

GGAC4100 is a photocatalytic air cleaner, meaning it cleans at the molecular level. AC4100 purifier

AC4100 creates photo ions that oxidize small particulate, destroy odor molecules, and kill microbes.

NOT trapped in a filter, GONE.

Left running in a closed small room, GG AC4100 WILL:
destroy mold spores and eventually eliminate colonies if humidity is kept low,
kill pollen,
kill germs and bacteria.

But raise the room size a bit and the whole scenario fails.

And 4100 does have a pretty good user review reputation for mild household odor situations, in small spaces.

But the key is, again, DO NOT over install the Guardian AC4100, 60 sq. ft. MAX!

The Guardian UV-C lamp is just TWO ( that's 2 ) Watts of power, seriously anemic.

At least there is a UV on/off switch.


AC4100 has NO ionizer.

Noise is louder than most expected, but numerous reviewers say "quiet, first two settings OK."

With dimensions of 7.5 x 6.5 x 11 inches, AC4100 is compact.

And light, at 3.9 pounds, easily transported to dorms or motel.

Cord length is 6 foot, some will say too short.

NOT an energy star, but still frugal.

Corporate and Warranty

Over the most recent decade, GermGuardian Technologies has prospered while most failed.

Guardian Technologies LLC
7700 St Clair Avenue
Mentor, Ohio 44060

Guardian's 1-Year Limited Warranty applies only to defects at time of sale and user pays shipping.

Where there is a visible "defect" GG will honor warranty, but this will be rare.

I think the build quality is above average, very few one star reviews piling up.

In my opinion, "Long Term Cost to Own," consisting of initial purchase price and annual maintenance, should be the criterion for judgment.

Does the semiannual maintenance cost, higher than the initial purchase price, dampen your enthusiasm for cleaner air?

It comes down to the buyer and their odor situation.

If your odor is moderate the UV-C could be "off" most of the time, particles are light enough for the 7 months to one year filter schedule, and the pet population is well behaved, you could have a winner with GermGuardian AC4100CA.


AC4100 purifier


tight footprint - small spaces
light-weight, easy to move
cheap purchase price


NOT for chemical sensitives
NOT recommended for larger areas
ongoing expenses

Best Applications

catbox hallway


GermGuardian AC4100 Table Top Tower at

GermGuardian FLT4100 Filter at

Where I see the roadblock for this device is when it comes time for a big commitment of money and effort to keep ol' 4100 performing for another 7 months.

NOW is the time to think about that day, and buy replacement parts ahead of schedule.

Right now (11/03/15) the small UV-C lamp is available ONLY at, I would consider buying the replacement bulb with the new purchase.

LB4100 is $14.99, plus about $6 for shipping, at Guardian:

GermGuardian LB4100 Lamp at Guardian Technologies site

AC4100AC is also sold at

GermGuardian AC4100 Air Purifier at

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