I have spent fourteen years crawling around houses with a particle counter in one hand and a clipboard in the other, and I can tell you the single most common mistake I see: people buy the machine and never think about the filter. This HEPA air purifier filter comparison is written for that person. It lines up two purifiers and two replacement filters, because those four things are the same purchase decision wearing two different hats. The machine is the down payment. The filter is the mortgage.
Related: Air Purifier CADR Explained: What The Numbers Actually Mean
The best value in this group for most homes is the Winix 5300-2, because a washable prefilter means you actually replace the HEPA on schedule instead of putting it off until the filter turns gray and stops moving air. But that is the short answer, and it only holds if you are buying a purifier at all. Two of the four products here are filters, and if you already own an AC4825 or a Levoit Core 300, the filter is the only row that matters to you.
PuroAir 240 HEPA Air Purifiers for Home Pets Bedroom - Filter 1,000 Ft²
HEPA filtration aimed at pet dander and bedroom use, with a coverage claim big enough for an open living area
The 1,000 sq ft number is a nameplate claim, not a CADR figure, so treat it as a ceiling and not a promise
Winix 5300-2 Air Purifier with True HEPA, PlasmaWave and Odor Reducing Carbon Filter
True HEPA plus a carbon odor stage, which is the combination that matters during smoke season
No washable prefilter emphasis here, so the HEPA interval depends on how disciplined you are
GermGuardian, Filter B HEPA Pure Genuine Air Purifier Filter
Genuine OEM filter that keeps an older Guardian tower running instead of sending it to the curb
You are locked into one brand's filter pricing for the life of the machine
Levoit Core 300-P Air Purifier Replacement Filter, Genuine Air Filters
Genuine filter for one of the better small-room machines on the market
If you put a Core 300 in a living room, no filter on earth will fix that mistake
Prices and availability were captured from Amazon Creators API and may change.
What is actually being compared here
Four products, two jobs. The PuroAir 240 and the Winix 5300-2 are complete purifiers. The GermGuardian Filter B and the Levoit Core 300-P are replacement filters for machines people already own.
That split matters because the buying logic is different. With a purifier, you are choosing an air-moving system and accepting whatever filter ecosystem comes with it. With a replacement filter, you are already married to the machine and you are deciding whether to pay OEM prices or gamble on a third-party clone.
The one number that ties all four together is CADR, Clean Air Delivery Rate. It is cubic feet per minute of clean air, and it is the only spec that predicts what happens in your room. Filtration percentage tells you how good the media is at the filter surface. CADR tells you how much clean air reaches your lungs. A unit with excellent media and a weak fan loses to a unit with good media and a strong fan every single time.
The PuroAir 240: big coverage claim, bedroom manners
The PuroAir 240 is marketed for homes with pets and for bedrooms, and its name carries a 1,000 square foot coverage claim. I want to be careful with that number, because coverage claims and CADR are not the same thing and the gap between them is where money gets wasted.
Coverage figures usually assume a standard ceiling height, a certain number of air changes per hour, and a fan running at its highest setting. Nobody sleeps with a purifier on high. If you run it on medium overnight, which is what most people actually do, you are getting a fraction of the rated airflow. That is not a knock on PuroAir specifically. Every brand does it. The lesson is that a purifier sized for a 1,000 square foot open plan is genuinely working when it is placed in a 200 or 300 square foot bedroom, and it is coasting when you expect it to scrub the whole downstairs.
Where this unit makes sense: a primary bedroom with a cat, a dog, or a pollen problem, run on a mid setting overnight. Where it does not: as the only air cleaning strategy for an entire floor of a house with a wildfire smoke event outside. For that, you want more machine than this.
One thing to verify before you buy any purifier, and I mean this literally: put your hand around the filter door while it runs on high. If you feel air leaking at the seams, that is bypass, and bypass is the number one failure I find on inexpensive units. Air that sneaks around the filter is air you paid for and did not clean. Check the seal before you check anything else.
The Winix 5300-2: the one with the carbon stage
The Winix 5300-2 pairs a True HEPA filter with a carbon odor-reducing layer and PlasmaWave. That combination is the reason I keep pointing people at this family of machines.
Here is why the carbon stage matters more than the marketing suggests. HEPA media is a mechanical filter. It catches particles: dander, dust, pollen, smoke particulates. It does not catch smells, because odor molecules are gases and they are far too small for the mesh. Odors need carbon, and the amount of carbon in a purifier is usually the difference between a machine that handles a litter box and one that just blows the smell around the room. When someone tells me their purifier "does not work," the honest answer is often that it is working fine on particles and doing nothing at all about the smell, because there is barely any carbon in the filter.
The other thing I like about the Winix approach is the prefilter concept. A prefilter catches hair and coarse dust before it reaches the HEPA, which is what lets the expensive media last. Any purifier that makes the prefilter easy to vacuum is saving you money every month, whether or not the spec sheet brags about it.
The trade-off is that you are buying into a filter ecosystem with its own pricing and its own replacement intervals. Buy the machine for the filtration. Budget for the filters before you decide it was a bargain.
GermGuardian Filter B: keeping an older tower alive
If you already own an AC4825, an AC4300, an AC4850, an AC4880, an AC4900, a CDAP4500, or an AP2200, this is your filter. It is the genuine GermGuardian HEPA Pure replacement, and it fits the whole FLT4825 family of machines.
Two things to say about it. First, genuine matters more than people think on these towers. A third-party filter that is two millimeters too thin will not seat properly, and a filter that does not seat properly gives you bypass, which means you have paid for HEPA media and are running a fan with a suggestion of filtration. If you go aftermarket, measure the gasket. If you cannot measure the gasket, buy the genuine one.
Second, the "removes 99.97% of pollutants" language on the box describes the media, not your room. It is the standard HEPA efficiency rating at the most penetrating particle size, and it is a real number. It is also a filter-surface number. A purifier with a great filter and a tired fan still delivers mediocre CADR, and after five or six years of service, that is exactly what an older Guardian tower is. New filter, old motor. That is still a reasonable deal compared to a new purifier, as long as you know what you are getting.
The genuine filter also includes the carbon layer these units use for odors and smoke smell, which is why it is the one I would pair with a smoke season rather than a plain HEPA-only clone.
Levoit Core 300-P: the right filter for the wrong room
The Core 300-P is the genuine replacement filter for the Levoit Core 300 series, and I have a complicated relationship with that machine.
As a small-room purifier, the Core 300 is one of the better budget buys out there. For a bedroom, an office, a nursery, it does what it says. For a living room, it does not, and no replacement filter fixes a sizing mistake. I cannot count the number of people who bought a Core 300 for an open-plan space, ran it for two months, and concluded that air purifiers do not work. The purifier worked. The room was three times too big for it.
So the filter recommendation comes with a condition. If you own a Core 300 and you run it in a bedroom, buy the genuine Core 300-P and replace it on the interval the manufacturer specifies, not when it looks dirty. Filter media loads from the inside. A filter that looks clean on the outside can be substantially loaded, and the way you notice is that the fan sounds the same while the air stops getting better.
If you own a Core 300 and you want it to handle a living room, buy a second purifier instead of a second filter. That is the honest advice, and it is cheaper than the allergy medication you will otherwise keep buying.
The real price is the filter, not the machine
Here is the rule I give every client: take the cost of the replacement filter, multiply by the number of replacements per year, and add that to the purchase price. That total is what the purifier costs. The sticker price is a fraction of it.
Most HEPA filters in this class are rated for roughly a year of normal use, less if you have pets, smoke, or construction dust, more if you vacuum the prefilter regularly. Over five years, a machine with a cheap filter can cost less than a machine with a premium filter, even if the premium machine is better built. This is not an argument for buying cheap filters. It is an argument for doing the math before you buy the machine, because once the machine is in your house, you have already lost the negotiation.
This is also why I care so much about prefilters. A washable prefilter that takes you thirty seconds to vacuum is the single best filter-cost reducer in this entire category. It is unglamorous. It also saves more money than any feature you will see advertised on a box.
Matching these four to a room
If you are buying a purifier for a bedroom with pets, the PuroAir 240 is the straightforward pick, and its coverage claim gives you headroom if you move it to a larger room later.
If you want the best all-around value and you care about smoke and odors as much as particles, the Winix 5300-2 is the one I would hand a client, because the True HEPA plus carbon stack is the combination that handles a real smoke season.
If you own a Guardian tower and it still runs, the GermGuardian Filter B is a repair, not a purchase, and a repaired purifier is almost always cheaper than a new one.
If you own a Levoit Core 300 and you use it in a small room, the Core 300-P is the correct filter. If you use it in a big room, buy a bigger machine and keep this one for the bedroom.
Trade-offs I will not pretend away
Every row in that table has a downside, and here they are without decoration.
The PuroAir 240 asks you to trust a coverage number instead of a CADR number, and I do not like that, even when the machine is fine.
The Winix 5300-2 commits you to one brand's filter pricing for years.
The GermGuardian Filter B keeps a machine alive that may be past its air-moving prime.
The Levoit Core 300-P is a genuinely good filter attached to a purifier that people constantly oversize into rooms it cannot handle.
None of those are dealbreakers. All of them are things you should know before you spend money.
The short version
Buy the machine for its airflow and its seal, buy the filter for its fit and its price, and never separate those two decisions. Check the current Amazon price on all four, do the five-year filter math, and pick the row that fits the room you actually have instead of the room the box describes.