GermGuardian AC4100 And AC4150 Air Purifier Hands-On Review And Comparison

Looking for a great air purifier for small rooms? If you’re considering the GermGuardian family of products you’re on the right track. But how do the AC4100 and AC4150 purifiers stack up?

In my review and comparison of the GermGuardian AC4100 and AC4150 models, I’ll tell you everything you want to know. I personally own and have tested both.

Because of this, I can give you my real and honest opinion. As they’re based on the same design and share the same basic platform I’ll cover both in the same review.

Getting to know the AC4100 and AC4150

GermGuardian AC4100 vs AC4900 vs AC4825

The AC4100 (left) is a small room purifier and the little brother to the larger AC4900CA (center). The AC4900CA is also the near-identical sibling to the very popular AC4825 (right). The AC4900 and AC4825 are recommended for medium-sized rooms. All 3 share a very similar design and most of the same features.

The AC4100 and AC4150 are similar models and part of a family GermGuardian air purifiers that are some of the most products on the market.

The AC4100 is a small room air purifier that’s the smaller sibling to the AC4900CA and its very popular twin the AC4825.

The two larger models are recommended for medium-sized models up to 155 square feet while the AC4100/4150 is designed for small rooms below 100 sq. ft.

GermGuardian AC4100 vs AC4150BLCA vs AC4150PCA comparison image
The 3 models are extremely similar in design and have identical performance. The BLCA and PCA models are designed to be a great fit for children and include a cool-looking LED night light that projects onto the room’s ceiling!

The AC4150 version is available in 2 different models: the AC4150PCA (pink color) and the AC4150BLCA (blue color). Both feature a top-mounted LED night light that projects 1 of 3 designs on your ceiling.

They’re aimed for use in children’s rooms and make a great choice for a bedroom.

Both are marketed for use in small rooms and feature a “3-in-1” design:

  • A true HEPA filter
  • Prefilter/charcoal filter
  • UV-C germ killing feature

A removable and replaceable filter is used just like the larger models, although smaller. A replaceable UV bulb is used as well (again, specific size for the AC4100).

Note that you can expect to pay about $15 more for the AC4150 depending upon current pricing.

AC4100 vs AC4150 features

Here’s a quick summary of the differences to know between these two very similar models.

Feature AC4100 AC4100PCA AC4100BLCA
Color Silver-grey Pink Blue
Fan speeds 3 3 3
Room coverage Small Small Small
UV-C feature Yes Yes Yes
Night light No Yes Yes
Ceiling projector No Yes Yes

As you can see from above, the only real differences between the two types are an additional night light projector and color choices. All 3 use the same replacement filter and UV bulb part numbers.

There’s no difference in their air cleaning performance.

Unboxing and first impressions


Unboxing the GermGuardian AC4100 and AC4150PCA

My AC4100 and AC4150PCA (pink kid’s air purifier) arrived! Time to give them the hands-on test. Both arrived well-packaged just like the other GermGuardian products I own and have come to love.

The packaging was great and the same as my other products from the company. GermGuardian uses recycled corrugated cardboard for the packaging inserts and it works well.

Everything looked great and the box even had helpful information about service part numbers on the box flaps.

Build quality

GermGuardian AC4100 and AC4150 comparison image

Before long-term testing and after unpacking, I inspected both to check out the build quality and appearance. Both are well-made, look nice, and give a good impression. Just like their bigger sibling the AC4900CA, they’re very modern and stylish.

I own and use several models from Guardian Technologies already, so I had the same expectations for build quality for these. The great news is that I wasn’t let down.

Fit and finish are great. They’re well put together and I couldn’t find any visible defects, gaps, or assembly problems at all. Both also worked great right out of the box.

GermGuardian AC4100 corner angle image

The finish on the AC4100 resembles a silver-gray simulated brushed metal appearance while the AC4150 models have a satin pink or blue finish.

The finish on the AC4100 is a modern and contemporary one: it resembles a brushed metal silver/gray finish. However, the AC4150 models feature a satin paint appearance.

In all cases my purifiers look great and would fit in just about anywhere!

Checking out the controls

AC4100 and AC4150 controls comparison image

The controls are super-simple to use and work well as I discovered in testing.

The AC4100 family uses a 3-speed rotary fan control for fan air cleaning speeds (low, medium, and high). The “UV” on/off switch enables the built-in ultraviolet light (UV) germ-killing feature.

The controls have a good, solid feel and aren’t at all “cheap” in everyday use. No complaints there from me! I was very happy with how well it works, despite the simplicity.

Specifications and CADR ratings

GermGuardian AC4100/AC4150 Specifications
  • Room size rating: 78 sq. ft (small room)
  • Clean Air Deliver Rate (CADR): 56/76/50
  • UV-C germ killing light
  • Titanium Oxide odor molecule remover
  • 3-speed fan control
  • True HEPA filter w/ activated carbon filter
  • Low-noise fan setting
  • Replaceable UV bulb
  • Simple rotary control
  • Push button on/off UV switch
  • Filter replacement reminder dial
  • UV bulb replacement indicator
  • Prefilter/carbon filter is replaceable separately
  • 1-year limited warranty
  • Replacement filter: FILTER E (FLT4100)
  • Replacement bulb: LB4100
  • (AC4150) LED multi-color ceiling projection night light
  • (AC4150) 3 night light character lenses included
  • (AC4150) Night light dimmer feature
  • Weight: 5.38 lbs (11.9 kg)
  • Cord length: 6 ft.
  • Control location: front
  • Size: 7.5 x 6.4 x 11.5″ (19 x 16.3 x 29.2 cm)

If you’re not already familiar with it, it’s helpful to understand more about the Clean Air Delivery Rate (CADR) standard used by the industry. This is a voluntary lab-tested rating of an air purifier’s cleaning ability.

GermGuardian AC4100 CADR ratings labelThe AC4100’s CADR ratings are shown here.

The AHAM is an organization that verifies the testing results of home appliances & performs lab testing for appliance manufacturers although it’s not required by law.

In simple terms, it’s a rating used to help you know before buying an air purifier’s effectiveness. The rating numbers mean “higher is better” as they’re lab tested using a series of tests to measure their air cleaning effectiveness.

For the AC4100, the air cleaning is somewhere around 1/2 that of average models like the larger AC4825 and other brands. 

It’s important to understand that smaller air purifiers like this simply can’t move as much air so they’re limited in their performance.

I bring that up so you can understand what smaller units are capable of. For very small rooms that’s fine – but if you’ve got more demanding air quality needs I strongly recommend spending more money for a more effective model. (It’s very important to have realistic expectations)

Setup and placement

GermGuardian AC4100 set up foam pads image

After unboxing the purifiers are ready to go. Just take a few seconds and attach the foam pads and that’s it!

Setup is extremely simple! Aside from unpacking the purifier, you’ll only have to attach the soft foam pads included. The HEPA filter and pre-filter are assembled as one unit and are pre-installed from the factory.

Some competitors like Honeywell need additional steps before first use, just so you know.

Note: You’ll need to provide at least 1 foot of unobstructed space in front of and behind the purifier for proper airflow.

At about 11.5″ tall in size, it’s small and fits well on small tables and shelves in my experience.

However, for best use of the night light feature, place the AC4150 model closer to the room center to project the night light image across a larger area of the ceiling.

Air cleaning performance

GermGuardian AC4100 dirty prefilter image

In testing the AC4100, it captured significant amounts of dust which is one of my biggest air quality problems. You can see the dirty pre-filter here. Look at how much dust it removed from my air!

I tested the AC4100 by using it regularly including while away from home. It works well in small bedrooms but obviously can’t match the performance of larger models, so I was realistic about my expectations (as I own and regularly use its larger siblings already).

However, it performed well and I definitely found it helpful for removing dust (my biggest problem), pollen, and more. My air was fresher, easier to breathe, and much more enjoyable.

Despite them being lower-cost and smaller purifiers, they’re still great little workhorses just like their bigger brothers, you could say!

Overall I’m quite happy with them.

As both are smaller purifiers they have a smaller amount of airflow as they use only 1 fan unlike their larger counterpart, the AC4900. That being said, if you use them in the correct size room you’ll get the same results.

AC4100 dirty vs unused HEPA filters comparison
Before and after comparison of the AC4100’s HEPA filter. Left: My old used filter after trapping a lot of use in testing over several months. It captured quite a bit! Right: A new HEPA filter. The AC4100 & AC4150  work well for removing airborne irritants and allergens.

GermGuardian AC4100 square feet coverage and room size

The AC4100/AC4150 models are recommended for small rooms less than 100 square feet in size.

The company doesn’t specify the sq. ft. size in the owner’s manual, but it has been said to be below 100 ft, which is about a 10 x 10 ft room in size. This also makes it a great choice for bathrooms and offices as well.

That’s comparable to one of its competitors, the Honeywell HPA060 which I reviewed and tested as well.

When used in a larger room it will take more time to cycle and clean the air depending on the difference in air volume of the larger room.

Filters used

GermGuardian AC4100 HEPA and prefilter image
The AC4825’s HEPA filter (seen here) section is made up of a folded, dense fiber material. It’s capable of excellent filtering ability and works well. The filter can capture almost 100% of all particulates in its airflow down to 0.3 microns in size! A pre-filter/odor trapping carbon filter is attached to the front.

A high-efficiency particulate air (HEPA) filter is used to remove the most common air contaminants you’ll have to deal with.

Here’s an example list of what the AC4100’s pre-filter/HEPA filter combination can remove:

  • Pet dander
  • Pet hair (thanks to the pre-filter)
  • Dust mite allergens
  • Pollen
  • Dust
  • Home construction particles
  • Smoke residue
  • Smoke odors
  • Chemical and organic odors
  • Chemical vapors

Basically, it’s a multi-stage filter process as the pre-filter/carbon filter can trap both odors and larger particles like pet hair and dust. The HEPA filter removes smaller particles like smoke elements, pet dander, dust mite products, and much more.

The pre-filter is a thin, mesh material that attaches to the HEPA filter using a type of Velcro attachment. It’s easily removed and can be vacuumed to remove dust or hair buildup.

GermGuardian uses a true HEPA filter meaning it performs to the HEPA standard: a whopping 99.97% of particles passing through it down to 0.3 microns in size are trapped.

That’s particles less than 1/1,000,000 of a meter in size!

It’s a great filter assembly and works well, although I did notice some “new product” odor at start-up. However, it went away after a few hours of use.

I’ve found that to be normal for many air purifier products in general.

Ultraviolet light (UV-C) germ killing feature

GermGuardian UV-C and Ti02 germ killing badges

The AC4100 family includes a feature GermGuardian air purifiers offer that most competitors don’t: a UV-C ultraviolet light (UV) germ killer. Using a special bulb and titanium oxide components the system works to irradiate germs passing through, rendering them inactive.

The technology works by affecting germ and other airborne microbes’ molecular and protein structures.

The UV feature only operates when the fan is running, however. You’ll need to set the fan switch to any 1 of the 3 positions for it to operate.

However, I do have one minor complaint here. When the UV-C feature is in use, there’s no front LED indicator like its bigger sibling the AC4900CA.

According to the company:

UV-C light technology works with filters to enhance the elimination of airborne germs. Titanium Dioxide is activated by the UV-C light to decompose remaining odor molecules
caused by smoking, cooking, and pets.Guardian Technologies

In other words, air passing through the purifier during airflow is exposed to the UV light. This damages a small some of the germs in the air while the unit is running.

This makes it possible to reduce sickness and respiratory problems caused by germs as well.

Does the AC4100 produce ozone?

Quite a few people have wondered if air purifiers can cause headaches. The fact is that a filter-based purifier like the AC4100, for example, doesn’t produce any harmful emissions.

The UV-C feature is completely optional and doesn’t present any hazards at all. Both models don’t produce any ozone.

Filter & UV bulb replacement & cost

Replacement indicator wheel

GermGuardian AC4100 filter replacement reminder image

Unlike larger models I mentioned earlier, there’s no electronic filter replacement reminder feature. However, a manual reminder wheel is built into the rear. Using a coin I set the month reminder 6 months ahead to mark when I needed to check the filter for possible replacement.

Bigger models like the AC4900CA and AC4825 have an automatic filter replacement reminder feature. Those models track time electronically and blink a light to show when it’s time to check the HEPA and pre-filter sections.

Unfortunately, that feature isn’t present in the AC4100/AC4150 models. To be fair, it’s also not available in the similar small-room HPA060 air purifier from Honeywell either.

To their credit, however, GermGuardian does offer a “date wheel” as a type of reminder. By setting the wheel 6 months ahead from the current month you can track when the date when you should check the filters for replacement.

Filter life and costs

AC4100 replacement filter options
Right: A complete filter replacement for the AC4100/AC4150 is the FLT4100 size E set. Left: As the prefilter section is removable, you can also save money and extend life by buying a replacement pack instead of the extra HEPA filter.

Filter life is roughly 6-8 months as recommended by the manufacturer. However, in my experience that varies a lot depending upon use. Heavy air quality problems like severe dust, cigarette smoke, and especially heavy airborne particles may consume the filter faster.

It’s not necessary to replace the HEPA filter section every time, which is great! You can also optionally purchase the prefilter/carbon replacement filter separately for more value.

However, it’s important to note that while the HEPA filter may have a long life, the odor and vapor trapping ability of the activated carbon is time-limited. You’ll need to replace them periodically for maximum performance.

Expect to spend around $18 or so for a complete single-unit filter pack (FLT4100) or around $13 for a 4-pack (FLT11CB4) of the prefilters.

There are also replacement filters sold by other companies, but you’ll need to be careful when shopping to get the same performance as sometimes non-original filter replacements aren’t as effective.

How to replace the filters

GermGuardian AC4100 filter replacement how to image

Filter replacement is easy and I found it to be a snap to do. It only takes a few seconds to 1) remove the rear grill by pushing down on the release tab, and 2) pull out the filter assembly using one finger.

Filter replacement is a snap, so no complaints there. You’ll only need your fingers to do so.

To replace the filters:

  1. Push down on the release tab at the top
  2. Swing the grill down and outward
  3. Pull the soft tab or use a finger to tilt the filter assembly out

That’s it! I replaced my dirty filter (both my HEPA and pre-filter, since both were old) and thought it was very pleasant to do.

Note that as I mentioned earlier, the prefilter section can be detached from the HEPA filter once it’s all out. A Velcro-type fastener is used around the edges to hold them together.

UV-C bulb replacement & pricing

GermGuardian AC4100 replacement UV bulb LB4100The GermGuardian replacement bulb #LB4100. Expect to pay around $25 or so for one when replacing it.

Replacement bulbs cost about $12-$15 or so. Bulb life is rated for 10-12 months but a few people reported shorter life. However, I haven’t had an issue so far during use with mine.

AC4100 rear UV bulb cover diagram
To replace a dead bulb, you’ll need to remove one screw on the bulb’s metal shield after removing the grill and filter assembly. The owner’s manual has great instructions on how to do so.

It’s easy to replace in my opinion – but then again, it’s something you won’t need to do for a long time, so don’t let it be a concern.

Owner’s manual quality

GermUuardian AC4100 owners manual image
Buyers will be greeted by a very nicely done and helpful owner’s manual. It covers all recommended use advice as well has maintenance, replacement filter & bulb part numbers, and help contact information.

The provided owner’s manual is actually very nice, and one of the best I’ve seen from products of its type.

It’s somewhat short in length but very detailed, clear, and helpful. Additionally, French and Spanish sections are included.

In it you’ll learn:

  • Basic operation notes
  • How to set the filter replacement reminder
  • Replacement filter & bulb part numbers
  • Power consumption (about 65W on high)
  • Specifications
  • How to contact the company for support

However, the purifiers are so easy to use there’s little to learn aside from the basics. Note that the AC4150’s manual also has notes about how to use the LED night light provided.

Noise levels during use

Yep, noise levels are one of the biggest selling points for air purifiers and other air quality products sold. To make matters difficult, as it turns out I’m a light sleeper so I took great interest in testing this as well.

Volume measurements

dB noise level meter measurement image
I measured volume levels with my No products found., performed at 1 meter (3.28 ft) from the purifiers (note that both are the same in noise levels).

Measurement/Speed Volume (dB)
Off (room noise) 39.3
Low 47
Medium 51
High 58

In practice, with the exception of the high setting, I found the AC4100/AC4150 to be pretty quiet and very comparable to other models I’ve tested.

If you’re a light sleeper like me you’ll enjoy the low setting. It’s quite low and barely noticeable in my opinion. Medium is pretty quiet as well.

A note about motor hum

As these purifiers use a motor driven by an electronic board that uses controlled pulses for speed control, there is a characteristic hum you’ll notice a bit.

That’s typical of many in the GermGuardian line but I haven’t found it to be an issue. To its benefit, it’s actually a bit lower than its larger siblings.

AC4150 night light feature

GermGuardian AC4150 night light projection examples

I tested the AC4150PCA’s wonderful night light. You can choose from 1 of 3 included designs to project on the ceiling, in addition to changing colors. It’s pretty neat, and a great addition to your kid’s room! A dimmer function is provided as well.

Evaluating the AC4150PCA, the pink model, was pretty fun. I was really curious about how well the night light would work.

The AC4150 models feature an RGB (red, green, blue) LED night light lamp with a single button control. The purifier includes 3 total “lenses” (plastic light projector caps) you can swap out to change projector designs.

How does the night light work? Is it worth the money?

GermGuardian AC4150 night light how it works

The AC4150 “Kids” model night light works by using 3 LEDs to project one of 3 cute designs on the ceiling. It uses a single push button control to turn it on or off, change colors & mode, and adjust the brightness. It’s a very cool feature and looks very nice in the dark! 3 projector caps are included.

I’ve not always been a big fan of night lights considering how plain or too bright some are, so I had a few doubts before testing the AC4150. It turns out I was definitely wrong about it – and I’m glad!

The night light works great and projects one of 3 cute designs on the ceiling:

  • Under the Sea: whales, sea creatures, and aquatic shapes
  • Twinkle Moon and Stars (my favorite!): a nighttime moon and star pattern
  • Sleepy Safari: palm trees and animals from the jungle and zoo

To change projector caps, you swap out one for another by rotating the cap away from the locked position. It’s easy to do.

When installed correctly the cap locks in place and can’t fall off of the purifier in case it gets bumped or moved.

The night light is easy to use and isn’t complicated, either. The push button control operates using either a push or push-and-hold method.

Push button operation Description/Night light mode
Push Mode change:
1. On (max. brightness)
2. Slow color change
3. Solid white
4. Solid green
5. Solid blue
6. Off
Push and hold Dimmer mode: rotates from bright to dark then cycles back to full brightness and repeats if held again

Is it worth the $15+ dollars or so more than the AC4100 model? In my honest opinion, yes!

It’s a rare feature I haven’t seen on competing products. I would have liked, however, to be able to place the projector at an angle. That’s my only gripe with it.

Because it points directly upward, if you want to cover the entire ceiling of a room, you’ll need to place it closer to the center of the room. Otherwise, part of the projected pattern will be lost on a side wall.

GermGuardian AC4100 vs Honeywell HPA060

One of the main competitors is Honeywell’s HPA060 small room air purifier. Here’s a quick summary of how the two compare.

GermGuardian Desktop Air Purifier for Home, H13 HEPA Filter, Removes Dust,...
Honeywell AllergenPlus HEPA Tower Air Purifier, Airborne Allergen Reducer...
Room size (sq ft)
~75 (small room)
75 (small room)
Filter type
True HEPA + prefilter/activated carbon
True HEPA + prefilter/activated carbon
Germ killer?
Filter reminder?
Yes (date wheel)
GermGuardian Desktop Air Purifier for Home, H13 HEPA Filter, Removes Dust,...
Room size (sq ft)
~75 (small room)
Filter type
True HEPA + prefilter/activated carbon
Germ killer?
Filter reminder?
Yes (date wheel)
Honeywell AllergenPlus HEPA Tower Air Purifier, Airborne Allergen Reducer...
Room size (sq ft)
75 (small room)
Filter type
True HEPA + prefilter/activated carbon
Germ killer?
Filter reminder?

Ultimately, in my opinion, the AC4100 and AC4150 are a better deal and offer just a bit more. Not only that, but the GermGuardian models often sell for less.

However, note that the HPA060 is less noisy on the Low setting but otherwise almost exactly the same volume.

After owning and testing both I’ve found the AC4100 to simply be a better value. The addition of a germ-killing feature is a plus that the HPA60 doesn’t offer.

The filters are the same type and the performance is the same, so why pay more?

Review score & summary

After testing I have to say the AC4100 and AC4150 models are well-made air purifiers that live up to the expectations set by their bigger brother the proven and popular AC4900CA. If your room isn’t very small (or if you have more than light air quality problems), however, I would strongly recommend stepping up to the AC4900 or AC4825 if you can afford them.

Check my review score below to see the pros and cons then head over to see why they’re also highly rated by others as well!

AC4150BLCA (Blue)
AC4150BLCA (Blue)
  • Quality - 9/10
  • Value - 9/10
  • Ease of use - 9.8/10
  • Air cleaning ability - 7/10
  • Features - 7.8/10
  • Noise levels - 7.8/10

Well-made and reliable, the AC4100 offers nice small room air purification for the money. The AC4150 adds a fun night light that kids will love.

The AC4100 and AC4150 aren’t flashy or fancy, but they get the job done well in small spaces they’re recommended for (~78 sq. ft ). They’re affordable and easy to use. A true HEPA filter and prefilter/activated carbon filter do well at trapping allergens, smoke, dust, and pet dander as well as odors and vapors. The AC4150 Kids model offers 2 unique colors and a fantastic night light I enjoyed. It’s a unique feature not found in other models. They’re relatively quiet with simple controls anyone can use. Unfortunately, while the germ killer feature is a plus, there’s no indicator light like on larger models. Great for offices, dorm rooms, and other small spaces for adults or children, they offer decent light duty air cleaning, but for greater air cleaning performance you’ll need to spend more.


  • Quiet operation
  • UV-C germ killing feature
  • Clear, detailed instructions
  • Attractive and classy appearance
  • [AC4150] Nice kids color options
  • Good build quality
  • Simple controls
  • Filter replacement reminder wheel
  • Easy filter replacement
  • Pre-filter can be replaced separately
  • True HEPA filter
  • Great for small tables or desks
  • [AC4150] Color changing night light
  • [AC4150] 3 selectable night colors
  • [AC4150] Includes 3 projection patterns
  • Priced less than several competitors/better value
  • No ozone production
  • Replacement filters are affordable


  • Low CADR rating/air cleaning performance
  • No UV-C on/off indicator light
  • No power light
  • No filter reminder light (like other GermGuardian models)
  • Reminder wheel requires turning unit around
  • [AC4150] Night light projector can’t be angled
  • No 3 yr warranty like AC4900, AC4825 models
  • Not as quiet as a few others (Levoit LV-H132)
  • [AC4150] Manual doesn’t mention dimmer function
Grant Williams

About the author

Grant is a professional engineer by trade and has experience with both maintenance and do-it-yourself home projects. He enjoys sharing his expertise & ideas with others to help them improve their comfort and quality of life. Read more »

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