GermGuardian AC4200W – An Tiny Air Purifier Review (2022)

I have been following the air purifier market for some time now. I couldn’t help but notice the many popular GermGuardian air purifiers. However, the downside that has turned me off, like many others, is the old-school and outdated design.

You’re probably wondering why I’m currently doing a review of a GermGuardian model? The answer is straightforward because the GermGuardian AC4200W is different; its aesthetics are much better. It seems like a significantly better air purifier than some of the older models.

GermGuardian AC4200W Air Purifier - Review
I placed this small air purifier on the small table.

In addition, I was drawn to the fact that this model does not have a UV-C light, which is an indispensable part of many GermGuardian models. The big jump in demand for air purifiers seems to have forced many manufacturers to look more closely at innovation and launch new models. This is a good sign for users, and we can expect many innovative air purifiers in the coming period.

I have done a full review and tested the GermGuardian AC4200W lengthwise and crosswise. Find out what performance it showed, how loud it is, and whether it is affordable for maintenance in this comprehensive GermGuardian AC4200W review.

Short on Time? Here’s My Short Summary of The GermGuardian AC4200W!

  • Suppose you are looking to upgrade your old GermGuardian with a new, more modern, and beautiful device. In that case, the AC4200W is a great device to consider.
  • The GermGuardian AC4200W is a True HEPA air purifier designed for rooms up to 105 sq. ft.
  • GermGuardian offers a 3-year warranty on this model.
  • The average filter life on the AC4200W is about 6 months.


The GermGuardian AC4200W air purifier is characterized by several specifications, which you can see in the table below.

Manufacturer Guardian Technologies
Model AC4200W
Dimensions 10.5 x 10.75 x 15.5 inches
Filters Carbon/Pre-filter Combination and True HEPA Filter
Filter Longevity up to 6 months
Room Coverage (4.8 ACH) 105 sq. ft.
Number of Fan Speeds 4 – Speed 1, Speed 2, Speed 3, and Speed 4
Power Consumption 26W
Warranty 3-year
User manual PDF

Setup and Installation

The GermGuardian AC4200W does not require much complex preparation before the first start-up. However, I would like to point out that preparing the filter before switching on the air purifier is mandatory. This is done by opening the lid at the bottom of the unit, removing the filter, unpacking the same filter from its plastic packaging, and returning it back into the device. That should be all, and your GermGuardian AC4200W is ready for use.

I would also advise you to be careful where you place the device; I suggest moving the device at least 12 inches away from the wall or other objects.

There is a red safety button in the filter component to check that the filter is set correctly. So if you do not set the filter correctly, you will not be able to start the air purifier.


As I mentioned at the beginning of the review, GermGuardian has taken a step forward in design with the AC4200W. Until now, their air purifiers have been using old-school design, but recently they have released several models that follow all modern design guidelines.

The build quality is excellent, the plastics seem hard and solid, and everything is in place. Every part is in place, and everything seems very well-tightened.

GermGuardian AC4200W Air Purifier On The Desktop
The GermGuardian AC4200W placed on the office desk.

The device does not have a carrying handle, but it is very light and small, so it will not be a problem.

The AC4200W is unevenly circular in shape; it is colored white except for the grey control panel on the top of the device. The white color, the modern design, and the overall impression allow you to integrate the GermGuardian AC4200W into almost any ambiance. And now you’ll be able to do that easier than with some older GermGuardian models.


The control panel is on the top of the device. The control panel has buttons and indicators. The buttons are touch-sensitive, very sensitive, and very easy to use.

GermGuardian AC4200W Air Purifier - Touch Buttons
This air purifier has controls located on the top.

You will find the ‘Power,’ ‘Speed,’ and ‘Timer’ buttons on the control panel. The fan speed button changes the motor speed with each press, the first speed is the sleep mode, and the last fourth speed is the turbo mode.


Although the GermGuardian AC4200W has an unusual circular shape, the vents are not positioned over the entire surface. The vents are located on the lower half of the device but only partially on the front and rear sides. It also has vents at the bottom. The GermGuardian logo is painted on the front panel. As mentioned earlier, the AC4200W draws air through the vents, which is then filtered and exits through the grilles at the top of the device.

Size and Dimensions

The air purifier weighs 6.55 lb. The dimensions of the device are: 10.5 x 10.75 x 15.5 in. It is a very small device, so it can easily be placed on a bedside table, desk, or shelf.

What’s in the box?

When you buy the device, you get a GermGuardian AC4200W air purifier, instruction manual, and True HEPA filter.

The AC4200W requires preparation before the first start-up, so I advise you to look at the beginning of the review, where I describe the steps necessary to complete before starting the device for the first time.


The GermGuardian AC4200W does not have advanced features to highlight that are innovative and unique to this device. It is, however, slightly more creative and different from the GermGuardian AC4825, which of the advanced features only has a UV-C light.

GermGuardian AC4200W Air Purifier - Features
The AC4200W is an old-fashioned air purifier.

To avoid prolonging the discussion, please see below for a description of this model’s individual options.


The timer is one of the options I have mentioned. Not very innovative, but very useful, especially if the device cannot connect to a smart app or if there is no auto mode. When you set the timer, the unit will switch off after a specified time. The AC4200W allows setting the timer to 2h, 4h, or 8h.

Filter Reset Indicator

This is a necessary option that makes no sense to omit on any air purifier.

The filter reset indicator essentially gives you “less hassle” it allows you to easily track and control the time when you need to change the filter. This means that the filter reset indicator on the control panel at the top of the unit will light up when it is time to change the filter.

Sleep Mode

The GermGuardian AC4200W has 4 speeds. The first speed is sleep mode. I really like the sleep mode on this model, but I honestly wish the motor volume is a bit quieter at this speed.

When you switch to sleep mode, the current speed indicator flashes for 5 seconds, and then all the indicators turn off. This means that you can easily use the GermGuardian AC4200W in a bedroom or other darkroom.


As I mentioned earlier, the AC4200W does not use UV-C light like some of the other models in the GermGuardian series. It does not use an ionizer or any other level of filtration that could produce illegal amounts of ozone.

The GermGuardian AC4200W complies with California’s very stringent legislation. It is irrefutable proof that this model does not produce harmful amounts of ozone and is entirely safe to use.

Energy Star Certified

Energy Star is the simple choice for energy efficiency, making it easy for consumers and businesses to buy products that save them money and protect the environment. This certification verifies this model’s energy efficiency and low power consumption of just 26W. You can see the confirmation of the energy efficiency and very low power consumption in the “Operating Costs” section.

Motor Protection Circuit

The GermGuardian AC4200W motor is equipped with a protection circuit that is activated if the motor overheats and if it is used for a certain period without switching off.

When the protection is activated, the motor switches off, but the indicators continue to work. In this case, the device must be reset; this is done by disconnecting the device and leaving it to rest for at least 10 minutes. Then you just need to switch it on, and that’s it; you have successfully reset it.

Room Coverage and CADR

The GermGuardian AC4200W is designed for rooms up to 105 sq. ft. In a room of this size, the AC4200W cleans the air as much as 4 times when running at maximum speed.

It is most effective in rooms of very small dimensions, but even larger rooms are not a problem for it, as it performed very well in the tests I carried out in a room of 194 sq. ft.

I would like to point out that the GermGuardian AC4200W is AHAM tested, which means that the clean air intake rate data is accurate and verified. The CADR for this model can be checked in the table below.

Smoke 68
Dust 76
Pollen 77

GermGuardian AC4200W Air Purifier Video Review

Check out in detail how GermGuardian AC4200W performs in the video above. It has great performance, but you can also discover that at some speed, the noise is a bit loud.

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Filtration Technology

The GermGuardian AC4200W uses a True HEPA filter in combination with an activated carbon filter. The filter is round in shape, and located at the bottom of the device.

GermGuardian AC4200W Air Purifier - Filtration Technology
I pulled out the filter so you can see how large it is in comparison with the device.

The first thing that caught my eye about the filter is the filter dimension which is very small compared to the device. A similar situation is with the TruSens Z-1000 filter, which is also much smaller than the device. 

GermGuardian AC4200W Air Purifier - Replacement Filter

GermGuardian AC4200W Replacement Filter

Always buy genuine filters for the best performance. As soon as the filter reset indicator is on, you are ready to change filters. Do it as quickly as possible.

Check Filter Price On Amazon

Honestly, I think that the manufacturers would have benefited much more if they had used a larger filter and that the device’s performance would have been much better in the long run.

GermGuardian AC4200W filters are not washable, so never wash them in water or rub them with liquid.

Activated Carbon and Pre-filter Combination

The first stage of filtration is a combination of charcoal and pre-filter. Its purpose is to reduce unwanted odors from pets, smoke, cooking fumes, and other terrible smells.

This combination is not always the best solution, mainly because the pre-filter needs to be cleaned frequently. The filter material breaks easily, leaving you in a situation where the whole filter needs to be replaced.

Another complaint is that this fiber filter is carbon-coated, which can absorb much less gas than a carbon pellet filter.

Overall, the AC4200W has not performed too badly on gas tests. It performs well in these situations. However, if this level of filtration could be improved, there would be better performance and greater efficiency.

True HEPA Filter

The last level of filtration is the True HEPA filter. It is commendable if a product in this price range uses a True HEPA filter, so I have nothing but praise for this level of filtration. A True HEPA filter captures 99.97% of microscopic allergens, dust, and mold spores down to 0.3 microns in size.

How to Replace the GermGuardian AC4200W Filter?

The filter reset indicator lets you know when it’s time to change the filter. The GermGuardian AC4200W has an average filter life of between 6 and 8 months. However, in my experience, due to the very small filter, I think it will get dirty much quicker, and you will need to replace it sooner. So I think that the filters on this machine will last a maximum of 6 months. In any case, the replacement time depends on the way the air purifier is maintained and the conditions in which it is used.

It is recommended to clean the pre-filter at least once a month as this prolongs the filter’s life and keeps the filtration at a constant high level. The carbon filter on this model is replaceable. Suppose you feel that the unit is losing performance in filtering gases. In that case, you can order as many as four carbon filters in the box and change them as needed.

Noise Test

When it comes to the noise produced by the motor on the AC4200W air purifier, I have to say that I expected less noise. What surprised me most was that the device is very loud in sleep mode when compared to some other competing devices.

GermGuardian AC4200W Air Purifier - Noise Test
I used a special noise measurement tool when performing noise level tests.

Other speeds are similar here and there and do not differ much from the range of competing devices. The AC4200W produces a sound of about 49.3 dBA in sleep mode and about 63.1 dBA at maximum speed.

The loudness at higher speeds can pass, but I think GermGuardian should have tried a little harder to optimize the motor’s performance in sleep mode.

In the table below, you can see detailed data of the loudness for each speed.

Speed Value (dBA)
Speed 1 49.3 dBA
Speed 2 59.5 dBA
Speed 3 61.3 dBA
Speed 4 63.1 dBA

Performance Tests

The GermGuardian AC4200W is an air purifier designed for rooms up to 105 sq. ft. This device is intended for very small rooms. Still, I must immediately point out that it has outperformed some other devices designed for rooms up to twice as large.

GermGuardian AC4200W Air Purifier - Performance Test
I used the Tmetop laser particle matter when have been testing performance.

To be honest, I was not expecting this kind of performance, but the AC4200W surprised me positively. Given the recommended dimensions, I tested the AC4200W in custom rooms. I did all the tests separately, but the principle is always the same.

120 sq. ft. Room Test

The first test was carried out in a 120 sq. ft. room.

This room is a shade larger than the recommended dimensions, so the AC4200W is expected to perform well. In 60 minutes of work, the GermGuardian AC4200W improved the air quality in this room by approximately 92% at maximum speed, lowering the AQI from 120 to 10.

# Starting Baseline After 60min
PM 2.5 91.5 7.9
PM 10 128.1 10.8
Particles 132776 11167
AQI 120 10

As I expected, this is an excellent result, despite the slightly larger than recommended room dimensions.

194 sq. ft. Room Test

For the second test, I installed the device in the same conditions but in a 194 sq. ft. room, which is larger than recommended.

As in the previous test, the device ran continuously for 60 minutes. It reduced the AQI from 125 to 12, improving air quality by approximately 90%.

# Starting Baseline After 60min
PM 2.5 95.4 9.3
PM 10 133.6 13.1
Particles 138432 13589
AQI 125 12

This is also an outstanding result, especially as the room is almost twice the recommended dimensions. The test in a room of this size is just proof that the AC4200W can cope with even more demanding challenges.

Operating Costs

The GermGuardian AC4200W is an air purifier with a power of only 26W.

This air purifier is Energy Star certified, which is proof that it doesn’t use a lot of electricity.

GermGuardian AC4200W Air Purifier - Operating Costs
The GermGuardian AC4200W uses a small motor of just 26W.

If you leave the AC4200W running at its maximum speed for 24 hours a day for a month, the machine will cost about USD 2.7. This cost is definitely not high.

Speed Power Usage (W)
Standby 0.2W
Speed 1 19.5W
Speed 2 24.6W
Speed 3 26.5W
Speed 4 30.8W

In addition to the cost of electricity, there is the cost of a filter replacement, which lasts on average up to 6 months. I advise you to maintain and clean the filter as often as possible to prolong its life and ultimately reduce maintenance costs.

FAQ on GermGuardian AC4200W

What is the warranty on the AC4200W?

GermGuardian offers a 3-year warranty on this model. I recommend that you register your device on the Guardian Technologies website to secure your warranty.

Does the GermGuardian AC4200W produce ozone?

The AC4200W does not produce unauthorized amounts of ozone and is entirely safe to use.

How often should I change the filter in this unit?

Depending on maintenance and the contamination of the room in which it is located, the filter on this model lasts up to 6 months.

Pros and Cons

To revise, here are the advantages and disadvantages of the GermGuardian AC4200W air purifier:


  • Excellent Test Performance
  • 3-year Limited Warranty
  • Does not produce ozone
  • 4 fan speeds with motor operation
  • Energy-efficient and very low power consumption
  • New, improved design
  • Good value for money


  • Considerably loud at some speeds
  • Lack of advanced options
  • It would be good if the filter was bigger


It is good to see one manufacturer continuously progressing and bringing new, innovative, and improved products to the market. GermGuardian is one such manufacturer, and the AC4200W is a model that brings many improvements and innovations to the brand.

In addition to its improved design, this model gives excellent performance and, above all, is energy efficient.

Suppose a loud motor at some speeds combined with a lack of advanced options is not a problem for you. In that case, my absolute recommendation is to buy the GermGuardian AC4200W air purifier. After all, it has excellent performance results, and the company gives a 3-year warranty on their product.



Review Breakdown





Operating cost


Value for money


Ease of use


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