Last week I was standing in my living room staring at the blinking red light on my Winix air purifier. The filter indicator was screaming at me, and I knew I had to track down the right replacement. After digging through specs and reading dozens of buyer reports, I landed on the Genuine Winix 115115 Replacement Filter A for C535.
It's the official drop-in replacement for several popular Winix models, and it matters which one you buy.
Worth it if you own a C535, 5300-2, or P300 and want the factory-spec performance without gambling on off-brand filters. Skip it if you have a different model entirely or are hoping for a cheaper third-party alternative. Let me walk you through exactly what this filter does, how it performs, and whether it fits your situation.
What it is
The Genuine Winix 115115 Replacement Filter A is a combined washable pre-filter and a True HEPA filter cartridge designed for specific Winix air purifiers. It is the official OEM part that replaces the internal filter assembly in the C535, 5300-2, and P300 models. The unit includes a grey foam pre-filter that captures larger particles like pet hair and dust, plus a pleated HEPA media that targets 99.97% of airborne particles as small as 0.3 microns.
Winix is a well-known brand in the air purification world, competing with names like Honeywell and Blueair. This filter sits in the mid-range segment of their lineup. It uses a straightforward drop-in design that requires no tools.
The carbon filter is a separate component on some models, but this replacement focuses on the core HEPA and pre-filter layers.
Setup and first impressions
The filter arrives in a compact box with the pre-filter already attached to the HEPA cartridge. Verified buyer reviews repeatedly mention that the packaging is simple and protective. The filter itself feels solid and well-constructed, with a dense pleat pattern across the HEPA media.
Installation takes about two minutes. You open the front grille of your Winix purifier, pull out the old filter, and slide the new one in place. The fit is snug and precise, which is a common complaint about third-party filters that are slightly too small or too large.
The pre-filter has a foam layer that can be vacuumed clean every few months, which extends the life of the HEPA media.
Users report that the purifier immediately recognizes the new filter. The filter reset button on the unit works as expected. The initial smell of new plastic or foam is minimal and dissipates within a few hours of operation according to most buyer feedback.
| Filter type | Combined washable pre-filter + True HEPA |
| Compatible models | Winix C535, 5300-2, P300, 5300 |
| Filtration efficiency | 99.97% of particles 0.3 microns |
| Recommended replacement interval | Every 12 months under normal use |
| Pre-filter care | Vacuum or hand wash, air dry |
| Dimensions | 13.2 x 8.9 x 3.5 inches |
| Weight | 1.2 pounds |
| Country of origin | China |
Daily-use experience
Performance
The filter does exactly what it promises. Aggregate user reviews consistently report a noticeable drop in dust and airborne particles after installation. The True HEPA media captures pollen, dust mites, pet dander, and mold spores effectively.
One reviewer noted that their allergy symptoms improved within a week of swapping to a fresh filter.
The pre-filter catches larger debris before it reaches the HEPA layer. This is important because it extends the life of the more expensive HEPA media. You can vacuum the pre-filter every two to four weeks.
The airflow remains strong even after several months of use, which is a common complaint with cheaper generic filters that clog faster.
The carbon filter is not included in this assembly. The C535 model uses a separate AOC (Advanced Odor Control) carbon filter that you need to replace separately. The 115115 handles the particulate side, not the odor side.
Build quality
The frame is made of a sturdy cardboard-like material with a plastic mesh backing. The pleats are evenly spaced and the media is taut. This is a marked difference from some third-party alternatives where the pleats can be loose or uneven.
The foam pre-filter is dense but not overly thick. It sits securely on the HEPA cartridge. The overall build feels durable enough to last a full year.
The edges are sealed properly, which prevents air from bypassing the filter media.
Noise and airflow
Users report no change in fan noise after installing this filter. The airflow restriction is within the normal range for a Winix purifier. The purifier runs at the same speed settings with the same noise level.
This is a good sign because a poorly designed filter can create additional resistance that makes the fan work harder.
Some buyers mention that the purifier sounds slightly quieter after replacing a heavily clogged old filter. That makes sense. The fan does not have to push as hard against a blocked filter.
Pros and Cons
✓ Pros
- Perfect fit for C535, 5300-2, and P300 models — no gaps or air leaks in the housing
- Washable pre-filter extends the life of the HEPA media by trapping dust and hair first
- Consistent airflow and filtration performance across the full year of use
- Easy installation that takes under two minutes with no tools needed
- Thousands of verified buyer reviews with a 4.7-star average rating that holds up over time
✗ Cons
- Does not include a carbon filter — you have to buy the AOC pellet filter separately for odor control
- Price is higher than generic alternatives, often by 20 to 30 percent
- Some users report the foam pre-filter can shrink slightly after repeated washing
Score breakdown
Who should buy it
Buy it if you
You own a Winix C535, 5300-2, or P300 air purifier and you want the filter that the manufacturer designed for that machine. You value consistent performance and a perfect seal over saving a few dollars. You also appreciate the washable pre-filter that reduces how often you need to replace the entire unit.
This is for people who set their filter on a yearly schedule and want to know it will work without surprises.
Skip it if you
You have a different Winix model that uses a different filter size. The 115115 will not fit in the HR900, 5500-2, or 9500 series. You are also probably better off with a different option if you are shopping on a strict budget.
Generic filters can be found for less, though they may not last as long or fit as well. And if you are looking for a combined HEPA and carbon filter in one unit, this is not that product.
Better alternatives
If the 115115 is out of stock or you want a different approach, consider the Winix AOC Carbon Filter separately. It handles the odor side of the equation. For a complete one-piece replacement, the Winix 115115H is the same filter with a slightly different packaging.
Generic brands like FilterStream offer compatible filters that cost less, but buyer reviews show more variability in fit and longevity.
Frequently Asked Questions (FAQ)
How often should I replace the Winix 115115 filter?
Winix recommends replacing the filter every 12 months under normal household use. If you run the purifier 24/7 in a high-pollution environment like a home with smokers or multiple pets, you may need to replace it every 8 to 10 months. The pre-filter can be washed monthly to extend the HEPA section's life.
Can I wash the HEPA filter?
No. Only the grey foam pre-filter is washable. The white HEPA pleated media is not designed to be washed.
Water will damage the fibers and reduce filtration efficiency. You can vacuum the surface of the HEPA gently, but do not submerge it or run it under water.
Does this filter fit the Winix 5300?
Yes. The 5300 and 5300-2 use the same 115115 filter. The 5300-2 is a slightly newer version of the same purifier.
Verify your model number on the back or bottom of the unit before ordering. The 5300 series is one of the most common Winix models, so this filter is widely compatible.
Does the filter include a carbon layer?
No. The 115115 is a pre-filter and HEPA combination. The carbon filter is a separate component on Winix models.
The C535 and 5300-2 use the AOC Carbon Filter for odor reduction. You need to buy that separately if you want to remove smoke, cooking smells, or VOCs.
What is the difference between the 115115 and 115115H?
The 115115H is the same filter sold in a different package. Some retailers carry the H version, which stands for "home" packaging. The filter dimensions, media, and performance are identical.
Choose whichever is cheaper at the time of purchase.
How do I reset the filter indicator after replacing the filter?
After installing the new filter, press and hold the "Filter Reset" button on your Winix purifier for about three seconds. The indicator light will turn off or change color. If the light does not reset, unplug the purifier for 30 seconds and try again.
Most users report the reset works on the first attempt.
Final verdict
4.5 out of 5 stars.
The Genuine Winix 115115 Replacement Filter C535 is the right choice for anyone who owns a compatible Winix purifier and wants a straightforward, reliable replacement. It filters as advertised, installs in minutes, and the washable pre-filter adds real value over the life of the product. The only reasons to look elsewhere are if you need a carbon filter included or you are on a budget that forces you to take a chance on a generic alternative.
For most people, the peace of mind that comes with an OEM filter is worth the extra cost. You know it will fit, you know it will filter, and you know it will last. If you have a C535, 5300-2, or P300, this is the filter to buy.
Affiliate disclosure: This post contains affiliate links. If you buy through one of these links, I may earn a small commission at no extra cost to you. It never changes my recommendation, I only suggest gear I'd actually buy myself.
1. Genuine Winix 115115 Replacement Filter C535
After researching dozens of user reports and comparing specs across multiple compatible models, the 115115 consistently comes out on top for reliability. It is the factory-approved part that eliminates the guesswork of third-party alternatives. If you just want your purifier to work as intended, this is the filter to pick.
