GermGuardian AC4825 Air Purifier Review

GermGuardian AC4825 Review

The GermGuardian AC4825 air purifier is tremendously popular – one of the best sellers online, in fact – but it’s what happened the first night my friend’s son put it to use that helped me put the finishing touches on this review.

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3-in-1 Air Cleaning, Charcoal filters, True HEPA filters, and UV-C

The GermGuardian AC4825 uses three methods to purify, or clean, air–hence the “3-in-1” in its name. At the first stage, air is sucked in through the pre-filter, which screens out the largest things like hair, large dust particles and lint. Air then passes through the activated charcoal or carbon filter. The second stage is the HEPA filter which filters out small particles. The final stage is the UV-C or ultraviolet light and Titanium Dioxide (TiO2) mesh which kills germs and breaks down odors.

The First Stage: Prefilter and Activated Carbon

Air first passes through the pre-filter screen. This is much like the screen on your window, though it may be a finer mesh. This traps hair, lint and the larger particles, keeping the filter from being clogged up too early. What is Activated carbon or charcoal? It is a form of carbon that has GermGaurdian AC4825 Filter Combinationbeen processed to increase its porosity or holes in its surface. Non activated carbon has less porosity. These pores help trap impurities in the air passing through the filter. After this, air then goes through the HEPA filter.

The Second Stage: HEPA filter

HEPA stands for “High Efficiency Particulate Air” or “High Efficiency Particulate Arresting”. There are many air filters available on the market, and some are more efficient at filtering air than others. HEPA simply means that the filter meets a certain filtering efficiency standard. In order to qualify as HEPA by US Government standards, the filter must remove 99.97% of all particles that are 0.3 microns in size. A micron is 1/1000 of a millimeter. So you can understand what this means, imagine if the air passing through the filter had 1000 particles 0.3 microns in size in it. Only 3 out of that 1000 can make it through the filter for that filter to be called a HEPA filter. If there are 100,000 particles in the air, then only 30 can make it through.

You really don’t want to consider any air filter system or air purifier that does not have a True HEPA filter. You would be simply wasting your money, time and peace of mind by buying a non true HEPA air purifier.

The AC4825 comes with an initial set of filters: an activated carbon filter and a HEPA filter. If you run the AC4825 continuously 24 hours a day, 7 days a week, plan on replacing the filters 6 to 8 months from now, and on a regular 6-8 month schedule after that. New filters start off white and turns grey to black over time. Once it turns dark grey or black, it’s time to replace it. No tools are required to replace the filters.

The Third Stage: UV-C and TiO2GermGaurdian AC4825 HEPA Filter Side View

After passing through the HEPA filter, the mostly clean air passes through the third and final stage. This consists of a metal mesh coated with Titanium Dioxide or TiO2, which is activated by an ultraviolet lamp or UV-C light. This is the latest technological innovation in consumer air purifiers.

This method is a way for the GermGuardian AC4825 to kill germs and break down any remaining odors the earlier stages did not catch in the air. The screen does not need to be replaced or cleaned. The PCO process has been found to be much safer than ionizing or ozone generating air purification methods. As a matter of fact, the state of California has banned ozone generators or air purifiers that generate too much ozone. More on this later. PCO is a relatively new technology to consumer air purification, as some purifiers that have been around a while don’t have this built in. This is an extremely desirable feature to have, and fortunately, the AC4825 has it built-in.

The UV-C lamp will need to be replaced yearly if you run the machine 24/7. This is true even if the lamp does not burn out. This is because the lamp degrades and gets weaker slowly over time. The AC4825 has a indicator light on the front/top that will flash continuously when it’s time to replace the UV-C lamp. Normally, the indicator light will stay on solid and not flash. You can still run this air purifier with the UV lamp off, and just use the carbon and HEPA filters and there’s even a button to turn the UV-C feature on and off at will.GermGaurdian AC4825 Filter View

The fresh, clean air now exits the machine and is ready for you to breathe!


This air purifier works great for people with severe allergies, even if they are home most of the time. Allergy sufferers will often see a positive difference in their breathing the first night they use it and a decrease in allergy attacks. Many people like this machine so much that they buy a second one. Allergy sufferers that wake up with headaches in the morning due to allergies and in spite of medication found that they no longer wake up with headaches when using the AC4825 in their bedrooms at night. The AC4825 is able to remove most or all smoke odors due to roommates that are heavy smokers. This air purifier works great on removing pet odors and pet dander from the air.

The GermGuardian AC4825 is extremely quiet on the two lower fan settings and emits a low hum akin to white noise, which makes it great for use in rooms when you are trying to concentrate on listening to music, the TV, sleeping or working like in your home office or at an office job. On the highest setting, it’s a little louder and sounds like a small tower fan.

It’s been proven to be a very reliable air purifier, with few reported failures, as measured as a percentage of total units sold, even if run continuously – 24 hours a day, 7 days a week.

It’s very lightweight and easy to move from room to room with its very comfortable built-in carrying handle.

A friend of ours had this to say about the AC4825:

“I bought this in May 2014 for use in my son’s bedroom. He works part-time outside – in Phoenix – at a paintball field and doesn’t like to do much laundry. I could hardly stand to go into his room and could even smell it down the hall. However, this has completely solved that issue. Instead, his room has a new car smell. I don’t know if that’s an odor put out by the air purifier or if it’s the smell of really clean air but it smells nice and certainly better than a teenage boy’s bedroom.
In addition, he’s suffered from congestion since he was an infant and is always sniffling or having to clear his nose. We had his tonsils removed, his adenoids removed, and had tubes in his ears all to help with ear problems and constant congestion from allergies. The first night we put this in his room he woke up able to breathe easily through his nose – something he hadn’t experienced in ages. He has run this 24/7 since on level 1 or 2 depending on what else he’s doing in his room.”

In the interest of giving a balanced and objective review, we looked for problems as well. Out of thousands of reviews we read through, only a tiny fraction had any issues with this product. Overall, it seems very well made and is highly reliable.

For the infrequent problems, the manufacturer’s site and the product manual contain contact and support information. The manufacturer and its representatives seem very responsive and helpful. The AC4825 comes with a 3 year limited warranty, which is pretty generous as many electronics these days come with only a 1 year warranty.GermGuardian-AC4825-Tron-ArtleyHome

When turned on, there is a very bright, blue Tron-like light band on the front of the unit, towards the top. If you are planning on using this in a bedroom at night and easily distracted by lights in the room, this could bother you. Just keep that in mind. The AC4825 can emit a chemical smell when it is new. Not all units have this problem. If it does, it’s typically due to out-gassing of the plastics that the unit is made from and is a common occurrence with products manufactured in China, where most molded plastic products are made these days. The odors should dissipate after a few days. If you find it objectionable, you may want to place the unit in the garage or outside (don’t let it get wet) the first few days to “air out” the plastics.

Beware of negative reports about how this air purifier doesn’t filter enough air for a 400 sq ft room! Remember that this machine is rated for a 155 sq ft room, so for 400 sq ft, you will need at least 3 of them! I cover the machine’s ratings in the next section, below. Some people complained about the cost of the filters. Ok, let’s look at that in detail. The manufacturer’s site says to replace the HEPA and carbon filter every 6 to 9 months. Let’s assume your air is pretty dirty and you replace the filter every 6 months. Replacement filters are about $30 as of the time of this review, or if you buy in bulk, the cost drops to $27.67, and this includes the prefilter/carbon filter and HEPA. The UV-C lamp should be replaced once per year at a cost of about $12 at the time of this review. So let’s add that up. $30 + 30 +$12 = $72 a year, or about $6 per month.


Capacity or Performance Ratings

The AC4825 is rated for a room size up to 155 sq ft. This would be a square room about 12.4 ft x 12.4 ft. It might be a rectangular room 12 ft x 12.9 ft, or 11 ft x 14 ft

It has a CADR (clean air delivery rate) of 100 for tobacco smoke. Higher CADR ratings are better, and 450 is the maximum possible rating. CADR or the Clean Air Delivery Rate is a rating of the volume of the purifier can filter. CADR is a rating of effectiveness of how efficient the air purifier is at filtering very small particles like cigarette smoke, dust, molds, and pollens from the air in the room.

If your room is larger, consider the AC5000, which has a CADR of 125 for tobacco smoke. It is rated for 193 sq ft. This is a square room just under 14 ft x 14 ft, or a rectangular room 12 ft wide x 16 ft long.

Energy Consumption

Electricity in our area costs 9.6 cents per Kilowatt hour (you can find your local rate on your last electric bill). At its highest fan speed setting the AC4825 uses 55 watts. That’s $46.25 a year or $3.80 a month if you run the machine 24 hours a day, 7 days a week.

Total Running Costs

Total annual costs to run the AC4825 including filters, replacement UV lamps, and electricity altogether will be $118.25 a year or $9.58 a month. Remember, these costs are at the highest fan setting, and most people will run it at one of the two lower settings. Lower fan settings means it uses less watts, so less electricity is used.


The unit has a large knob with three fan settings: low, medium and high. There is a single button that turns on or off the UV-C light. You can run the AC4825 with or without the UV-C lamp on. An indicator light on the top tells you if the unit is on. It will flash continuously when it’s time to replace the UV-C lamp. Normally, the indicator light will stay on solid and not flash.

Other Features

The AC4825 uses a Titanium Dioxide (TiO2) screen in conjunction with the UV-C lamp to kill airborne germs, mold, viruses and bacteria. See the discussion above in the section “The Third Stage: UV-C and TiO2”

The power light is also an indicator light to let you know when the filter needs changing. Filters can be changed without tools. Changing the UV-C light requires a screwdriver to remove the protective metal shield.

GermGuardian AC4825 Dimensions

10.25 inches long x 6.75 inches wide x 21.5 inches high.

Weight is 8.7 lbs and has a handle on top to carry it from one room to another. Most air purifiers do not have a handle so this is a very handy feature if you only have one air cleaner but multiple rooms. It’s also a very comfortable handle – nice and deep so you feel you have a sturdy grasp when moving from room to room which can be done easily with one hand.


UV-C bulb part number LB4000, AC4825 replacement HEPA and Charcoal (carbon) filter FLT4825 Filter B


• Lots of features for the price
• True HEPA
• UV-C lamp
• Simple controls
• Runs quietly
• Filter & UV-C replacement indicator lights


• Small unit and capacity – rated for up to 155 sq ft.
• May have True HEPA filters, but there are no seals between the housing and the filter frame, allowing contaminates to leak past the filter.
• Some units emit plastic smell that may not go away, or takes a while to go away.
• If your air is extra dirty, you will need to replace the filters more often than every 6 months. Cost of filters can add up.

Consumer Review Ratings

Generally, consumers rated this air cleaner extremely high. It is a best seller with many retailers. For the Small Room, under $100 category, I give this unit our Best Buy Rating. This unit is meant for smaller rooms. If your rooms are larger you will need multiple units, or a different, larger unit.

GermGuardian AC4825 Price

Best price was Amazon (roughly $10 less than Walmart at the time of this writing). Who should buy this? People who want an inexpensive (under $100) high performance air purifier with the latest technology (UV-C and TiO2), and are looking for something to clean the air in a room no larger than 155 sq ft. Larger homes with larger rooms will need several of these units, or a different air purifier – something much larger, and more expensive.



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