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The GermGuardian AC4825 air purifier (also called the 3 in 1) has been one of our highest-rated air purifiers of the year.

But that doesn’t mean it’s the perfect one for you. It’s not for every home or set of requirements.

In this review, we’ve covered what it’s best at, and who it’s best for, including room sizes, the material you most want to filter (dust, smoke, pet dander, germs?), how much you want to spend on an air purifier, and more.

If you’re looking for a quick summary, here goes:

The GermGuardian AC4825 is the lowest cost air purifier verified by both and AHAM, (the two most important rating bodies for these machines) that we could find. It might not look as fancy as newer models, but it has the fan speed and filtration capacity to handle dust, smoke, and odors in rooms up to 153sq ft. If you want an affordable machine for a small room, you won’t regret it.

For our full review, see the table of contents below, or keep on scrolling.

What Makes the GermGuardian AC4825 Stand Out?

Germ Guardian True HEPA Filter Air Purifier with UV Light Sanitizer, Eliminates Germs, Filters Allergies, Pollen, Smoke, Dust Pet Dander, Mold Odors, Quiet 22 inch 4-in-1 Air Purifier for Home AC4825E

You’ve got 100 air purifiers to choose from… why would you consider this one?

The first reason to consider a GermGuardian AC4825 – I think the main reason – is the price.

Is it the best air purifier you can buy? No. But for the technology, the capability and the energy star rating of it, the GermGuardian AC4825 is among the best value air purifiers you can get for use in small to medium rooms.

We’ll get to the specifics in a second, but that’s the first thing you need to understand. There aren’t many air purifiers that will do as good a job as this one, for a price as good as this one.

The GermGuardian AC4825 is one of the best-selling air purifiers on Amazon. With a 4.3 star rating and over six thousand reviews at time of writing, it’s fair to say that the AC4825 has been well tested, and well liked. If you like proven quality and durability, these stats should be comforting.

Key Features of the GermGuardian AC4825

The GermGuardian AC4825 is a 22-inch-tall air purifier that cleans dust and particles out of the air as well as kills viruses and bacteria using a three-step process.

We’ll return to the 3 step process in one more sentence, but first, think about that size. This is a tower-shaped air purifier that’s meant for sitting on floors. It’s too tall to sit up on a bench or table or desk, so if that’s what you need, consider something more compact like a Levoit air purifier.

Ok, the filters:

First, the air enters through the back, hitting the prefilter and activated carbon layer. This first filter catches all of the large particles and pet dander and kills odors from animals or smoke.

Second, the air goes through a HEPA filter that catches fine particles like pollen, pet dander, dust mites, and anything that might trigger your allergies. And third, a UV-C light kills airborne bacteria and germs that can cause allergies and diseases.

Sounds great, but is all that stuff just a gimmick? How is this different than the filter in my HVAC system? I mean, do charcoal and a fancy light bulb really do anything to improve air quality?

The short answer is yes, all of the technology in the GermGuardian AC4825 serves specific and important purposes.

The first filter is important for two reasons: it filters the large particles while increasing the lifespan of the HEPA filter, while the activated carbon part increases air quality by eliminating odors. The first filter helps by catching the large particles and pet hair, which can then be cleaned off or the filter can be replaced much more easily than the more expensive HEPA filter.

The next filter layer is called the HEPA filter. HEPA stands for High-Efficiency Particulate Air. In order for a filter to be HEPA, it is required by law to filter 99.97% of particles that are 3 microns wide. 3 microns is incredibly small, and your standard HVAC home filter cannot come close to those numbers. HEPA filters keep the air clean that goes into your car’s engine. Doctors also use HEPA filters when handling tuberculosis patients and when dealing with other contagious viruses and bacteria.

You could pretty much turn your home into a cleanroom using the GermGuardian AC4825. The only downside to the HEPA filter is that it can be expensive to replace (and needs to be replaced every 6-8 months)

The final layer of air purification is the UV-C light. Ultraviolet-C light is sometimes called “ultraviolet germicidal irradiation.” The light kills things like bacteria, viruses, and germs. UV-C light has been used for a long time for sterilizing medical instruments and purifying water. Recently though, companies like Guardian Technologies have adapted it to purify the air. Not only does the light kill germs, but it also activates titanium dioxide in the AC4825 which decomposes other harmful molecules.

Oh, and lastly, it has an energy star rating.

Does All of This Technology Actually Work?

Absolutely, yes.

You will be amazed at how fresh and clean the GermGuardian AC4825 can make a room feel. And you will be amazed at the types of smells it can clear from a room. Some people even use the GermGuardian AC4825 for cigarette smoke. I don’t smoke myself, but some people have said it will clear the cigarette smell from a smoker’s house in less than a day. If it can do that, then it can do anything, and it does.

It eliminates pet odors, pollen, and dust. If you live in a basement, the GermGuardian AC4825 will make the stale air crisp and refreshing. This is a perfect air purifier for people with allergies who have reported feeling like they can finally breathe in their own homes.

What About Those Negative Reviews?

If you were looking at the AC4825E on Amazon, you might have noticed that despite having thousands of positive reviews, there are a handful of very negative reviews at the top of the list, where people talked about the product creating a fire hazard.

While the company has failed to comment on these reviews, it’s clear that some percentage of these units are faulty. The exact same problem has been reported and documented repeatedly. The latest of these reports is from this year, so it’s clear the issue hasn’t yet been resolved.

When it’s this kind of faulty – an inner circuit board overheating and causing the plastic casing to melt – it’s hard to justify taking a risk on this product.

Could you purchase it and be really careful? Not leave it running for too long etc? Could you bet on the issues being a few faulty units? Sure, but why bother, when by spending slightly more you could get an air purifier like the Coway Mighty, where no such issue has been reported?

Of course, it’s up to you, but that’s our word of caution.

How Do You Use the GermGuardian AC4825?

The GermGuardian AC4825 is very easy to use and understand. It comes in the mail completely assembled and ready to go with the filters already in place. Just plug it, turn it on, and choose your power setting.

Most people put the AC4825 away from the wall so that it can get good circulation throughout the room, and some even put it in the middle of the room.

The manual says that the GermGuardian ac4825 can be used in a room up to 155sq feet, or about a 12-foot by 13-foot room size. But don’t be afraid to use it for a larger space. Most people have found that it improves air quality in much larger spaces, so long as you allow it more time to run. I would recommend having at least one for every 600sq feet of the house.

Check out the video below to see the AC4825 in action.

What Is the Cost of Filters, Where Do I Get Them, and How Often Do They Need to Be Changed?

When you see a blinking red light on the top of the AC4825 air purifier, then it is time to change the filter. You can expect to change the filter about every 6 to 8 monthsChanging the filter is very easy and doesn’t require any tools. Just take the back off by pushing on the clip near the top and pull. The plastic back will come off and reveal the filters. Both filters can be removed at the same time. After you remove the filters, you can see the special UV-C light bulbs near the top. The bulbs should last a long time.

It’s kind of important that you use the Guardian Technologies replacement filters for the AC4825 since the HEPA filter is the most important part of the whole device because it’s what grabs those particles 3 microns or smaller from the air. Replacing the HEPA filter with a cheap off-brand filter would be like replacing a flat tire on your car with a bicycle wheel.

New filters are normally listed at $34.99; however, you can usually find them cheaper on Amazon. It’s best to have one or two extra filters handy so that you can easily swap them out when your red light starts blinking.

You can also make your filters last longer by cleaning them. You cannot wash them in the sink like you can with a cheaper filter, but you can vacuum the HEPA filter. I recommend using a vacuum on the carbon filter and the HEPA filter every month. You can also replace the carbon filter cheaply on a more regular basis.

How Noisy is the GermGuardian AC4825?

Compared to other air purifiers, the AC4825 performs at an average rating for noise.

There are decibel ratings but they can be hard to interpret before you buy. (How loud exactly is 24db? It depends on how sensitive your ears are and how close to the air purifier you intend on sitting, cooking, sleeping!) I’ve always found it more meaningful to look at user reviews for information about the noise, and the consensus with the AC4825 is that the machine is quiet at higher speeds and very quiet at low speeds (that you would use at nighttime). 

This makes sense too because it’s nowhere near the largest air purifier or the one with the most wattage.

What is the Warranty?

The GermGuardian AC4825 air purifier has a three-year limited warranty. The warranty, of course, does not apply to the filters or the UV-C bulbs, which are designed to be replaced.

What Are the Cons of the GermGuardian AC4825?

One of the major downsides to the GermGuardian AC4825 is that there is a little window at the top that lets the UV-C light shine through. This blue light is really distracting in a dark room. It is not ideal for trying to watch a movie or sleep. And yes, this light is safe to look at, it’s just a poorly thought-out design feature. The easiest way to stop the blue light is to turn off the UV by pushing the button on the top, but then you don’t get the benefits of the UV-C light sterilizing your air! Some people put dark tape over the light window, which does a great job of blocking the light. I would recommend using electrical tape or black duct tape.

Some people worry about the UV-C lights in the GermGuardian AC4825 emitting ozone. Fortunately, this is not an issue. The UV lights emit light at a lower frequency than what is possible to emit ozone. The GermGuardian AC4825 is an ozone-free machine!

Some people who have bought this air purifier say they have the blinking red light right out of the box. Do not worry, nothing is wrong with your machine. All you have to do is reset the light by holding down the button for 3-5 seconds. Once the indicator is reset, then it is good to go!

Another common complaint that some people have is that it has an air outlet issue. They say that air only comes out of one side of the machine. There is nothing wrong with the machine, that’s just how it works! The way the fan inside is designed means that it only blows air out of one side.

How Does It Compare?

GermGuardian AC4825 vs AC5000

Well for one, both these air purifiers are currently unavailable 🙂 See my note at the top of this post and try the AC5250PT instead 🙂

The only OTHER differences between the GermGuardian AC4825 and the AC5000 air purifier are size and price. The AC5000 is 28 inches tall compared to the 22-inch-tall AC4825. The manual states that the AC5000 can be used in rooms up to 193sq feet, or about 14 by 14 feet. Of course, just like the AC4825, most people use it in even larger spaces. I would recommend one AC5000 for every 900 square feet of floor space.

GermGuardian AC4825 vs AC5350

The difference here is a bit of quality and size. The AC5350 air purifier is the same size as the AC5000 at 28 inches tall and it can handle about 1000sq feet of floor space. One advantage of the AC5350 over the AC4825 is that it has a nice digital display that gives you more control. The AC5350 has five power settings, while the AC4825 only has three. And I know that beauty is in the eye of the beholder, but the AC5350 is just a better-looking model. Of course, you pay a lot more for those extra features.

GermGuardian AC4825 vs AC4100

There is a big difference between the AC4825 and the AC4100 air purifier. The AC4100 is very small, at only 11 inches. It’s half the height of the AC4825. The smaller AC4100 is made for sitting on a desk or table and is built to clean air in small rooms. The AC4100 should only be used for spaces of about 100 square feet.

GermGuardian AC4825 vs AC5250PT

The GermGuardian AC5250PT is very closely related to the AC5350. It is 28 inches tall, compared to the AC4825 at 22 inches, which means it can clean a larger space. It also has a digital screen and more settings, like five power levels. The AC5250PT air purifier is also able to clean a room a bit faster than the AC4825.

GermGuardian AC4825 vs AC4900CA

The only difference between these two units seems to be the design. The AC4900CA is a bit more minimalist and geometric compared to the AC4825.

GermGuardian AC4825 vs Winix 5500

There are a number of differences between these two models.

First, you will notice that they look a lot different. The Winix is a wide and flat air purifier, while the GermGuardian is skinny and tall. The Winix also has some extra features over the GermGuardian, like a timer and an extra power setting. One major difference is that the Winix comes with a remote so that you can control the power setting from anywhere in the house. The Winix is also designed for much larger rooms, covering a size of 360sq feet.

These differences come at a price, though. You could almost buy two GermGuardians for the price of the Winix 5500-2.

GermGuardian AC4825 vs Purezone

The Purezone air purifier and the GermGuardian AC4825 have a number of differences. The Purezone is a desktop or tabletop model designed for small rooms. It’s supposed to be compact and convenient, but for covering a smaller space.

Despite being much smaller, the Purezone is quite a bit more expensive than the AC4825.

GermGuardian AC4825 vs Honeywell HFD-120-Q

There are large differences between the Honeywell air purifier and the GermGuardian. The major difference is that the Honeywell does not have a HEPA filter. The GermGuardian’s HEPA filter traps 99.97% of particles, while the Honeywell does not. The upside to the Honeywell is that its filter is permanent and washable.

GermGuardian AC4825 vs Honeywell 50250-S

The major difference between the GermGuardian and the Honeywell air purifier is that the latter does not use UV light to kill bacteria and mold like the GermGuardian does. The Honeywell 50250-S does use a HEPA filter like the GermGuardian and does a good job of filtering particles, but it doesn’t have the germ-killing power of the AC4825.

GermGuardian AC4825 vs Coway AP-1512HH

The Coway AP-1512HH air purifier is currently our number 2 rated air purifier of 2020 so it takes a lot of beating.

It uses a HEPA filter just like the GermGuardian but does not have UV light for killing bacteria and mold. Some users consider this a benefit especially in light (pun intended) of the blue light issue we mentioned above.

The Coway covers a wider area and is a little smaller and more convenient. It has a very similar filtering style and capacity, minus the UV-C light feature. It’s more expensive, which mainly reflects the higher build quality and better feature set. Given that the AC4825 isn’t currently available, the Coway Mighty is your best buy for medium to large-sized rooms.


The GermGuardian AC4825 is a high-value energy star-rated air purifier. It is able to clean air in ways that its competitors can’t and for a price that competitors won’t beat.

After you’ve installed the GermGuardian AC4825, the air in your home will be fresh and crisp and clean in less than a day, and as long as you replace the filters regularly, it should stay that way. Plenty of reviewers report having had this air purifier for years.

This thing is perfect for smoking houses, people with pets, people with allergies, or just anyone who wants to have a better life in their own home. I highly recommend the GermGuardian AC4825 three-in-one air cleaning system if you are looking for an air purifier for your home.

If you’re ready to grab one, you can click here to see today's price for a GermGuardian AC4825 on Amazon.

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