GermGuardian AC4825 Air Purifier Review – Hands-On Test & Details

After having to deal with dust and other air quality issues, I picked up a GermGuardian AC4825 of my own. It wasn’t hard to find – after all, it’s one of the most popular purifiers sold today.

In my GermGuardian AC4825 review I’ll help you decide if it’s a good buy or not. I own it and I’ve put it through its paces personally.

I’d love to help you make the best buying decision for your money and experience better air at home just like I have. Believe me when I say a good air purifier is a great buy – but you’ve got to shop wisely.

Unpacking & first impressions


GermGuardian AC4825 packaging and unboxing image

My AC4825 arrived quickly and after removing it from the shipping box, inside was a purifier I’d come to love soon enough. It’s well-packaged and the owner’s manual is placed right on top to be sure you find it easily. Eco-friendly recycled corrugated cardboard is used for the packaging and it’s easy to unbox. We’re off to a great start!

I’m no stranger to air purifiers and home air quality products, so I didn’t think I would get excited about another air purifier. It turned out I was wrong.

For some reason, it was still fun to pick up my AC4825 from the UPS Store for the first time and unbox it. What is it really like, I wondered? How well does it work?

It arrived well-packaged and features recycled cardboard inserts that hold it in place. The owner’s manual is right on top so you can’t miss it when opening it up the first time.

Build quality and fit & finish

GermGuardian AC4825 closeup quality image
After opening and unpacking it (which consisted of removing the corrugated cardboard inserts – styrofoam isn’t used with this one) I finally got to check it out and turn it on.

The AC4825 is built with a solid, good-feeling ABS plastic body and has a nice low-gloss black finish. The top features a matte silver finish with a satin black top section surrounding the controls.

I didn’t get any kind of impression of it having any poor-quality construction or any similar flaws. It looks good, and honestly, I’m happy with it.

Personally, I’ve never been a big fan of shiny finishes on products like this, so it’s a relief that it doesn’t stand out in a flashy way in the rooms I’ve used it in.

I have to say it’s well put together and well-made. Parts line up well, are tightly assembled, and there aren’t noticeable gaps or quality control issues to speak of.

Overall, it looks like it cost more than I spent.

If there’s one thing I’ve learned over the years, it’s that gaps and misaligned parts are a sign of build issues. There’s none of that here.

Checking out the controls

GermGuardian AC4825 top down view of controls
Operating the AC4825 is extremely easy. In the picture above, you can see 1) the 3-speed fan control, and 2) the ultraviolet-light (UV-C) germ killing feature button switch.

The fan control feels great, and the switching is somewhere between a “soft” feel and a firm feel. It’s not too light, and yet not too hard to turn. I’m pretty happy with it, because it doesn’t feel like you’re going to miss position #2 and skip over to #3, for example.

The fan switch is actually quiet in operation and smooth to use.

The ultraviolet light (UV-C) germ killing feature

The AC4825, like several other GermGuardian air purifier models, features a bulb and titanium-oxide germ killing feature which radiates germs passing through it and renders them inactive by affecting their molecular and protein structures.

However, you’ll have to manually turn on this option.

To do so, the purifier must be at least in position #1 (low speed) before the control will work. You can tell it’s on by the glowing blue trim around the body as pictured here.

GermGuardian AC4825 side view UV-C feature glowing

When activated, you’ll see the small, thin light strip on the base of the silver decorative top glow blue from the inside. Don’t worry though – you’re not in any danger from exposure to ultraviolet light. It’s safely contained inside.

I like how this feature is used as a decorative accent when active. That’s a nice touch!

One complaint I have, however, is that once it’s in use, switching the purifier off and then on again won’t re-activate the feature.

You’ll have to do so manually, as there’s no memory feature (unlike some competitors) to restore the setting the next time you switch it on.

While not a “deal-breaker”, that’s a small detail to be aware of.

Specifications & CADR ratings

GermGuardian AC4825 Specifications
  • Room size rating: 167 sq. ft (medium room)
  • UV-C germ killing light
  • Titanium Oxide odor molecule remover
  • 3-speed fan control
  • True HEPA filter w/ activated carbon filter
  • CADR (Clean Air Delivery Rate) ratings: Dust (118), pollen (125), smoke (108)
  • AHAM Verified & Energy Star Certified
  • Low-noise fan setting
  • Replaceable UV bulb
  • Dual-section blower fans
  • Simple rotary control
  • Pushbutton on/off UV switch
  • Filter replacement reminder
  • UV bulb replacement indicator
  • 3-year limited warranty
  • Replacement filter: FILTER B (FLT4825)
  • Power use: 55W (max. fan speed)
  • Carrying handle
  • Weight: 8.65 lbs
  • Cord length: 6 ft.
  • Control location: top
  • Size: 6.75 x 10.25 x 21.5″

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 AC4825 air purifier CADR ratings AHAM label

The AC4825’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.

In the case of this model, the specs are good and you’re assured you’re getting proven performance.

Size and thoughts on using a “tower” purifier

AC4825 purifier measuring height

At nearly 22″ in height, it’s not a small device. “Tower” air purifiers are simply those that are taller and don’t have a low-profile design and stand tall on the floor.

They’re taller due to having more fans to provide more airflow.

It’s important to make sure you have enough room before buying. A great place is near a door and not backed into a corner in the room.

Be sure to give it lots of room (about 2 feet in front and back) as it needs space to circulate air efficiently.

Carrying the purifier

GermGuardian AC4825 being carried by handle

One thing I like is being able to carry it easily from place to place at home using the built-in carrying handle area. At the rear of the top, there’s a recessed area where your fingers have plenty of room to pick it up securely.

It’s a nice touch I didn’t notice at first bout after moving it around to find the ideal place in my home, I found it handy.

AC4825 power use measurements

Image of GermGuardian AC4825 power use being measured

Pictured: I measured power use (in Watts) for all 4 recordings (3 speeds plus off).  I recorded power meter readings both with and without the UV-C feature switched on. Overall, it uses a relatively small amount and it’s not an energy hog at all.

How many watts does the AC4825 use?

Unfortunately, the owner’s manual doesn’t go into detail about energy for the various modes you can use.

Rather than guess, I measured power use in Watts for all speed settings with and without the UV-C feature switched on. Note that the UV-C option uses about 4W of power (larger models use 8W).

Mode Power Use, UV-C Off Power Use, UV-C On
Off 0 0
High 46.4W 50.6W
Medium 42.2W 46.4W
Low 38.6W 42.7W

Overall, it doesn’t use much power at any setting although it’s a bit more efficient on high or medium. For those speeds, the fan is running faster and you’ll get faster air cleaning. The drawback is a bit more noise.

As the UV-C feature uses only about 4W, there’s no need to worry if leaving it on all the time will affect your energy bill.

Air cleaning ability & performance

GermGuardian FLT4825 dirty filter vacuum example image

My purifier’s filter (the FLT4825 filter that’s installed at the factory) trapped a HUGE amount of dust! You can prolong the pre-filter life by vacuuming off excessive dust or hair as needed, which I did. Dust is a really big air quality problem in my home and the AC4825 made a big difference when in use.

I’ve let it run all day while at work so I could come home to fresh, clean air, and it works well. Where I live I have to suffer every day from heavy dust which I absolutely hate!

The purifier’s filter picked up a HUGE amount of dust and did well to relieve my problems, in addition to capturing light odors well, too.

As far as odor absorption performance goes, it’s not on par with more expensive models like the Winix 5500-2, but it’s pretty good for everyday needs in my opinion.

The thing to remember is that air purifiers work by cycling air in a room and it takes time to cycle & filter the entire room’s air.

GermGuardian AC4825 square feet coverage and room size

This model is recommended for room sizes that are medium in size. That being said, there’s absolutely no reason it can’t be used in a small room!

You’ll find that it cleans the air even faster in that case.

It’s sized for rooms about 167 square feet in size which is roughly a 10 x 16.5 ft room. Bear in mind that this is an approximate size used – it doesn’t have to be used in a room exactly that size.

When used in larger rooms the amount of time required to fully cycle and clean the air increases depending on the amount of space inside the room.

Filter ability

GermGuardian AC4900CA filter close up

The AC4825’s HEPA filter (seen here) section is made up of a folded, dense fiber material. A second section, the pre-filter/activated carbon filter is responsible for trapping larger particles as well as odors and volatile organic compounds (VOCs) in the air. It’s capable of excellent filtering ability and works well. The filter can capture nearly 100% of all particulates in its airflow down to 0.3 microns in size!

The high-efficiency particulate air (HEPA) filter is fantastic for removing the most common air quality issues (especially those that cause allergies!).

Here’s the basic list of air contaminants the AC4825 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

Essentially, this is a 2-stage filter assembly made up of 2 parts: the pre-filter/activated carbon filter and an extra 2nd section, the HEPA filter, for a total of 3 filters.

The pre-filter section is a less dense & thin section covering the active carbon filter. Its job it to capture larger items in the air like pet hair, dust, and so on before they reach the HEPA filter.

The active carbon filter traps odors and other chemical substances in the air.

Finally, the HEPA filter captures an amazing 99.97% of particles passing through it down to 0.3 microns in size. That’s less than 1/1,000,000 of a meter!

That means it’s capable of capturing elements that are much smaller than you can see with your eye (microscopic).

It’s a great filter and works well. I noticed fresher air soon after using it for the first time, and I’m pleased with it.

The UV-C germ killing feature

GermGuardian UV-C and Ti02 germ killing badgesBy touching the UV button on top, you switch on the germ killing feature. It’s a great addition not found in many competing products.

It’s also perfectly silent and doesn’t cause any noise or produce any side effects.

When on, the blue trim on the base of the silver top section glows blue to show the bulb is working. The technology works using the science of ultraviolet light (UV) to affect microbes in the air, coupled with titanium dioxide to remove airborne contaminants.

As stated in the owner’s manual:

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 the remaining odor molecules
caused by smoking, cooking, and pets.Author

Essentially, air passing through has the UV light irradiating into it and microbes in the air are destroyed. It can help prevent sickness and other respiratory problems caused by germs.

Does the AC4825 produce ozone?

Some people wonder if air purifiers can cause headaches. The truth is that air purifiers that use a filter to clean the air don’t produce emissions to cause unwanted effects.

The UV-C option is completely enclosed and you’re in no danger of skin UV exposure. The AC4825 is perfectly safe and healthy as it does not produce unsafe ozone levels.

In fact, it produces 1/20th of the level considered acceptable by the Health Canada Guideline 2010 based on exposure levels & time considered acceptable.

You’re perfectly safe and won’t have to worry about ozone while using it.

Filter & UV bulb replacement indicators & cost

Replacement indicator lights

The purifier features a helpful way of indicating when it’s time to check and possibly replace the filters. After about 6 months of use, the green LED near the fan switch will blink red to indicate this (see the chart below).

If your filter has had very light use and isn’t heavily used, you can reset the indicator by holding the UV-C button for 5 seconds.

In the case of replacement for the UV-C feature bulb, the blue light will blink.

Blinking Light Type Meaning
Blinking blue light (UV-C glow trim blinking) UV bulb needs replacement
Red blinking light The filter needs check/replacement

Filter life and costs

GermGuardian FLT4825 replacement filter
The FLT4825 is
the genuine replacement filter from GermGuardian. It includes both the HEPA filter and an active carbon filter section, too. While the genuine replacement filter is only around $30+, you can save money by buying 3rd party replacement filters.

Expect to replace a filter after about 6-8 months; however, this depends greatly on use. For example, if you’re a smoker or have indoor pets you can expect to replace the filter when reminded.

For situations where the air quality demands are lower you’ll get even more life out of it.

Replacement filters cost around $30 (or a bit over that) for the genuine GermGuardian brand. However, 3rd party budget models are available which contain 1 less expensive filter or 2 filters in the box. If you’re concerned about maintenance costs that’s a great option.

How hard is it to replace the filter?

GermGuardian AC4825 filter removal image
Filter replacement is easy and only takes a few seconds. I was pleasantly surprised by how easy it is.

It’s just a few simple steps:

  1. Press down on the release tab on the rear cover
  2. Pull the cover down and out (there are 2 tabs on the bottom which rest in tab slots)
  3. Using your fingers, pull the filter out and down to remove it
  4. Replace the filter using the opposite motion
  5. Insert the cover’s tabs in the base
  6. Swing the cover up and snap the release tab back in place

…and you’re done! I’ve demonstrated this in my video review as well, so be sure to watch that if you’re interested.

UV-C bulb replacement & pricing

GermGuardian AC4825 UV bulb cover diagram

UV bulb replacement is pretty straightforward. The owner’s manual clarifies what you’ll need to do for bulb replacement (which is typically after 10-12 months). You’ll need a Phillips screwdriver (not included) to remove 2 screws, unplug the old bulb, and insert then a new one. Overall, it’s pretty simple to do, so don’t worry about it. Additionally, if you rarely use the feature you’ll never have to do it, anyway.

LB4000 UV replacement bulb
The GermGuardian replacement UV bulb #LB4000. Expect to pay around $25 or so for one when replacing it. The company’s life rating is 10-12 months, although a few owners have reported shorter life (which unfortunately is a problem with many bulbs in general).

Replacement bulbs cost about $25. To replace the bulb, you’ll need a Phillips head screwdriver to remove the rear metal bulb cover. It’s accessible once you’ve removed the filter after opening the cover.

Once the metal cover is removed you simply slide out the old bulb and replace it with a new one. Overall, it’s easy to do.

The bulb is rated at 10-12 months of life expectancy, although a few owners have reported that their bulbs died after only a few months.

The owner’s manual

germguardian ac4825 owners manual image
I was pleasantly surprised to find that the purifier included a solid, well-made owner’s manual with clear instructions and helpful information. Basic information like replacing the filter, UV bulb servicing, and user operation is clearly explained.

After unboxing my new purifier I reviewed the instructions and found the owner’s manual to be very clear and helpful. It is provided in English, French, and Spanish. At only 20 pages long, it’s fairly concise, but it’s good. The manual tells you the basics you need:

  • How to operate your purifiers
  • The indicator lights (power, air filter replacement reminder, and UV light bulb replacement)
  • Replacement filter model specifications
  • Power consumption
  • Specifications: size, weight, and square feet coverage

The English section is very clear and helpful. It contains 12 pages of information you’ll want to review before operating it, but honestly? This model is so easy and hassle-free to use you won’t need instructions though, honestly!

Don’t worry, I won’t leave any of the specifications off – I’ll provide them below.

(If you like, you can download the GermGuardian AC4825 manual here for your convenience)

Noise levels during use

The manufacturer claims that the unit has low noise during use and in my testing I found it to be mostly true.

  • Low speed (#1) is indeed fairly quiet, and suitable for sleeping if you’re a light sleeper like me
  • Medium (#2) is not very loud. It’s hardly noticeable at all if I’m watching YouTube or listening to music
  • High (#3) has a moderate level of noise and can be masked by the sound of your TV or radio. However, it’s fairly noticeable but not loud.

The high setting is especially helpful for fast and maximum cleaning of contaminated air. Smoke, dust, and more come to mind.

It’s honestly very quiet and I’ve found it pleasant-sounding when in use. While not as quiet during low-speed like a few competitors such as the Levoit LV-H132, I’m happy with it.

The main reason that the AC4825 is a few decibels louder is that it has not one but 2 fan sections and produces a bit more sound. Two fans move much more air than 1 and therefore, of course, add a little bit more noise than one alone.

That’s a trade-off when using a more powerful purifier like this.

Volume measurements

dB noise level meter measurement image

I measured volume levels using a No products found. at 1 meter (3.28 ft) from the purifier.

Measurement/Speed Volume (dB)
Off (room noise) 39.3
Low 42.5
Medium 50.5
High 58

A note about the sound while running

I do have one minor gripe: while in operation, and although it’s fairly quiet, there’s a characteristic sound these devices produce.

Because of the dual-fan section design as well as both the motor and its electrical drive, the combination of these factors causes it to produce a “whirring” noise while in use. The noise isn’t annoying or bothersome in my opinion, but it’s something to be aware of beforehand.

Night brightness

Image of GermGuardian AC4825 in dark

The top-facing power-on LED is a green soft-glow type of indicator. It’s not too bright, but still slightly noticeable in the dark. The blue glow is produced when the UV-C feature is switched on and isn’t very bright, but the human eye is more sensitive to blue light.

For that reason, my opinion is that for many people it will be fine, but if you’re especially sensitive to light when concentrating on a task on sleeping it could be an issue.

In that case, I recommend leaving the UV turned off during those times or moving it out of the way where you can’t notice it.

Not to worry though: the light brightness isn’t enough to “light up a room” or something unacceptable like that. Instead, it has a soft glow that’s not a problem in my opinion.

The AC4825 vs AC4900CA – A cool looking twin worth checking out

germguardian ac4825 vs ac4900ca image

The AC4825 (left) has a cool-looking twin, the AC4900CA (right). It’s identical in features and performance. Interestingly enough, sometimes one model is priced lower than the other and you can save a few dollars!

You might not know this, but the AC4825 has a sibling called the AC4900CA, which is identical in performance, features, and specifications.

I’ve seen it sold for a few dollars less (for example here at Amazon) and I think the styling is nice.

It’s well worth considering, as while not as popular as its counterpart it has the same great quality and is otherwise identical.

AC4825 vs AC5000 comparison

GermGuardian AC4825 vs ac5000 comparison photo

The “big brother” to the AC4825, the AC5000E is nearly identical except for room size coverage and the UV-C bulb. It’s a great addition to your home as well. Be sure to check out my detailed comparison if you’re interested in the AC4825 but have a large room!

In case you’re not familiar with it, the AC5000 is almost identical except for its size (near 28″ tall) and better room coverage. It too is an excellent large-room air purifier and is recommended for rooms up to 193 square feet in size (med.-large).

Just like the AC4825, it features a UV-C germ killing feature although the bulb design is different.

GermGuardian AC4825 vs the Honeywell HPA100

Honeywell HPA100 air purifier image

The closest rival to the AC4825, in my opinion, is the Honeywell HPA100. It offers some features the GermGuardian doesn’t, although it’s lacking in a few areas. It’s also available in a white version. Room size coverage is 155 sq. ft.

In my opinion, the AC4825 is a solid, well-built, and easy-to-use purifier. However, there’s no shortage of competition. Although it can’t come close to the popularity of the AC4825, the Honeywell HPA100 is a solid contender with about the same room size coverage.

As I’ve reviewed several other Honeywell models like the HPA160 you see here, I can’t verify their quality and they’re pleasant to use.

Some of the features the HPA100 offers that the AC4825 doesn’t are:

  • Electronic touch controls
  • A Turbo high-speed setting
  • Auto-off timer

However, there’s no germ killing feature offered. That’s absent in the Honeywell HPA series of purifiers, and it’s a shame. You’ll also pay a few dollars less for the GermGuardian model as well.

Additionally, the pre-filter in the HPA series is a little bit more thin than the GermGuardian family uses. The touch controls of the HPA100 are nice to have but to be honest, I’ve haven’t missed them at all.

I still use my AC4825 regularly and find it so simple and easy to use…it’s still one of my favorites! However, if having an auto-off timer is an important feature for you, it’s worth your while to check out the impressive reviews for the HPA100 at Amazon today.

Review summary

Honestly, I’ve got very little to complain about with the AC4825. It cleans the air well, it’s extremely simple to use, and it’s quiet. I love it!

The AC4825 makes enjoying clean, fresh air easy and affordable.

Image of AC4825 with Editor's Choice award badgeWatch out for high prices, however! Head over to find the current sale price (and get free shipping!) at Amazon.

  • Quality - 9.2/10
  • Value - 8.9/10
  • Ease of use - 10/10
  • Air cleaning ability - 9/10
  • Features - 7.5/10
  • Noise levels - 8.8/10

A well-performing air purifier that you'll be glad to own. No wonder it's one of the best-selling models today.

The GermGuardian AC4825 is a no-frills tower air purifier with simple operation and good air cleaning ability. It lacks a few fancier features when compared to more expensive models, but it’s a better value. Room coverage (med. rooms, 155 sq ft) is better than many similarly priced competitors.

Quality and build are very good; maintenance is easy to perform. It’s a quiet and pleasant-sounding purifier in my testing. The prefilter/HEPA filters work well to remove airborne particulates and odors. The UV-C feature is a bonus germ-killing option. One of the best-selling air purifiers available today, it’s a solid, sensible choice for fresher air.


  • Great air coverage for its price range
  • AHAM Verified & Energy Star Certified
  • True HEPA filter + prefilter/carbon filter
  • Easy to operate
  • UV-C feature kills germs
  • Carry handle built-in
  • Filter & UV replacement reminders
  • 3-year warranty
  • Maintenance is easy to perform
  • Low operational noise
  • White version available
  • Prefilter/carbon filter separately replaceable


  • UV-C feature has no memory feature
  • No auto mode or auto-off timer feature
  • Blue glowing trim could be noticeable to some with high sensitivity
  • Tall height may not be suitable for all users
  • Rotary manual control fan speed switch
  • You’ll need to buy 3rd party filters to save money as originals are more expensive
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 »

Your comments are welcome!

  1. I have had mine for about 6 or 7 years and I use it every night all night long. The sound is perfect for getting me to sleep to block out outside noise while cleaning the air. But I’m thinking I should order another one soon in case they go out of production. How long do they generally last (in years)? Does anyone know please and thank you?

    • Hi Kathleen. It’s hard to say exactly, but I wouldn’t be surprised if it lasts 10+ years – or as long as the motor can last. I’ve had some that were already several years old and still ran great (& quietly) so I think that’s a pretty good estimate.

      Because they’re so popular I don’t think it should be too hard to find them on the used market if when that time comes. Best regards!

  2. Wonderful read!! I put a lot of thought into my AC4825 Guardian purchase and was happy until… I was concerned after reading an article that stated UV was not worth it, dangerous to have the mercury in the home, and not effective with hepa filters I was about to return my newly purchased air purifier from Guardian when I came across your article. I am pleased to say I feel I made the correct purchase and am keeping it!!!
    Thank you


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