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Here's something most filter brands won't tell you: not all airborne threats are created equal. Bacteria can be up to 50 times larger than viruses — and that size gap changes everything about how your air filter performs. Based on our experience manufacturing millions of filters across four U.S. facilities, we've seen firsthand how the right MERV rating makes a real, measurable difference in what gets trapped and what slips through.
Below, we'll share what we've learned from over a decade of building and testing filters — including which MERV ratings target bacteria, where viruses present a trickier challenge, and the practical steps you can take right now to better protect your home's air.
The bottom line from our team: After manufacturing millions of filters at every MERV level, we've seen MERV 13 deliver the most meaningful improvement for households concerned about airborne bacteria, allergens, and respiratory virus protection. No filter eliminates every pathogen—but the right one captures the particles that carry them.
Recommended action: Upgrade to a MERV 13 filter and change it every 60–90 days for consistent whole-home protection.
Bacteria and viruses both travel through indoor air, but they're fundamentally different in size — and that's the key factor in filtration. Bacteria typically range from 0.3 to 10 microns, making them large enough for quality pleated filters to capture effectively. Viruses are significantly smaller, often between 0.02 and 0.3 microns, and they frequently travel attached to larger respiratory droplets rather than floating freely.
Understanding this distinction is the first step toward choosing a filter that actually does the job you need it to.
MERV — Minimum Efficiency Reporting Value — measures a filter's ability to trap particles within specific size ranges. Here's how the ratings we manufacture at Filterbuy line up against bacteria and viruses:
MERV 8 (Standard) captures dust, pollen, and larger debris. It provides solid everyday protection but isn't designed to target most bacteria or viruses.
MERV 11 (Superior) begins trapping finer particles, including many common bacteria, pet dander, and mold spores. For households with pets or mild allergy concerns, this is where noticeable improvement starts.
MERV 13 (Optimal) is where filtration gets serious. At this rating, filters capture particles as small as 0.3 microns at high efficiency, which covers the vast majority of airborne bacteria and many virus-carrying respiratory droplets. From our experience testing across our U.S. manufacturing facilities, MERV 13 consistently delivers the best balance of air quality improvement and HVAC system compatibility for residential use.
Here's where we'll be straight with you: no standard residential HVAC filter eliminates all viruses. Individual virus particles are simply too small for even MERV 13 to catch on their own. However, viruses rarely travel solo — they're almost always attached to larger moisture droplets, dust, or other particles that a MERV 13 filter can effectively capture.
That means a high-quality MERV 13 filter significantly reduces your exposure, even if it can't promise 100% removal. It's one of the most practical steps any homeowner can take without modifying their existing HVAC system.
After building filters for over a decade and hearing directly from millions of customers, our recommendation comes down to your household's needs:
If your main concern is general home maintenance and dust control, MERV 8 handles the basics well. If you have pets, seasonal allergies, or want better protection against common bacteria, MERV 11 is a meaningful upgrade. And if you want the strongest residential defense against both bacteria and virus-carrying particles — without restricting airflow or stressing your HVAC system — MERV 13 is the filter we'd put in our own homes.
The easiest way to stay protected is to change your filter every 60–90 days and choose the highest MERV rating your system supports. Not sure which that is? Our team can help you figure it out in minutes.
"After manufacturing millions of filters across our four U.S. facilities, we've seen the data firsthand — MERV 13 consistently captures the vast majority of bacteria and virus-carrying droplets in real-world conditions, making it the strongest practical defense most homeowners can add without any modifications to their existing HVAC system."
— Filterbuy Team
We get it—when you start researching air filtration and pathogens, things can get technical fast. So we pulled together the seven most useful resources from the EPA, CDC, and ASHRAE to help you cut through the noise. Each one backs up what we've covered in this article, and together they'll give you everything you need to feel confident about protecting your home's air.
EPA – Guide to Air Cleaners in the Home (2nd Edition) https://www.epa.gov/indoor-air-quality-iaq/guide-air-cleaners-home
Not sure where HVAC filters end, and air purifiers begin? This EPA guide sorts it all out. It compares your main options for reducing airborne contaminants—including bacteria, mold spores, and virus-carrying particles—without drowning you in jargon. If you're just getting started with indoor air quality, this is the resource to bookmark first.
EPA – Air Cleaners, HVAC Filters, and Coronavirus (COVID-19) https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-hvac-filters-and-coronavirus-covid-19
A lot of people don't realize their existing HVAC system can help reduce airborne pathogens—with the right filter. This EPA resource explains how filters capture the respiratory droplets that carry viruses, and why they recommend MERV 13 as the minimum for meaningful pathogen reduction. It's one of the clearest explanations out there of how filtration fits into a layered defense for your home.
EPA – Residential Air Cleaners: A Technical Summary (3rd Edition) https://www.epa.gov/sites/default/files/2018-07/documents/residential_air_cleaners_-_a_technical_summary_3rd_edition.pdf
This one's for the homeowner who likes to see the numbers. The EPA's technical summary shows exactly how different filter ratings stack up across particle sizes—from the larger bacteria range down to the sub-micron droplets that carry viruses. It's more detailed than the general guide, but still organized in a way that makes sense if you want real data backing your filter choice.
ASHRAE – MERV Rating System (Standard 52.2) https://www.ashrae.org/technical-resources/filtration-disinfection
ASHRAE literally created the MERV scale, so there's no better source for understanding what those numbers actually mean. You'll learn how filters are tested across three particle size ranges (0.3–1.0, 1.0–3.0, and 3.0–10.0 microns)—which maps directly to where bacteria and virus-carrying droplets show up. This is the resource that explains why MERV 13 hits the sweet spot for most homes.
CDC – Improving Air Cleanliness Through Filtration https://www.cdc.gov/niosh/ventilation/prevention/air-cleanliness.html
The CDC doesn't mince words here: upgrade to MERV 13 when your system can handle it. This page lays out their filtration recommendations for reducing airborne bacteria and viruses, and explains why pairing better filters with regular HVAC maintenance creates a much stronger defense than either one alone. Practical, specific, and straight from the nation's top health authority.
CDC – Ventilation and Respiratory Viruses https://www.cdc.gov/niosh/ventilation/about/index.html
Here's something most people miss: the best MERV rating in the world won't help if your filter is clogged or overdue for replacement. This CDC resource explains their recommendation of 5 air changes per hour for reducing viral transmission—and why staying on top of filter replacements is just as critical as the rating itself. It's a good reminder that consistent maintenance is half the battle.
EPA – Preventing the Spread of Respiratory Viruses in Indoor Spaces https://www.epa.gov/indoor-air-quality-iaq/preventing-spread-respiratory-viruses-public-indoor-spaces
This EPA guide was written for commercial and public buildings, but the core principles translate perfectly to homes—especially if someone in your household deals with allergies, asthma, or a compromised immune system. The takeaway? Combine MERV 13 filtration with good ventilation and regular filter changes for the strongest protection against airborne pathogens. It's the same layered approach that health authorities recommend across the board.
After more than a decade of manufacturing air filters in the U.S. and shipping millions to homes nationwide, we've seen firsthand what's really going on with indoor air. These numbers reflect the real-world challenges we help customers solve every day.
The U.S. EPA reports that indoor air can be 2 to 5 times more polluted than outdoor air. That lines up with what we hear from customers all the time—they're surprised by what's actually floating around their homes.
Common culprits hiding in plain sight:
Our takeaway: A filter change isn't just a chore. It's one of the simplest ways to protect your family's comfort and health.
(Source: U.S. EPA – Introduction to Indoor Air Quality)
According to ASHRAE Standard 52.2, MERV 13 filters trap up to 90% of airborne particles in the size range where bacteria, mold spores, and common allergens live.
From our experience manufacturing filters at every MERV level, here's what we've found:
Our takeaway: If you're only going to make one upgrade, this is the one we recommend most.
(Source: ASHRAE – Standard 52.2: Method of Testing for Filter Performance)
To lower respiratory virus particle concentration indoors, the CDC recommends a minimum of 5 ACH (Air Changes per Hour) through a combination of:
What most homeowners don't realize is that upgrading your existing HVAC filter is one of the easiest and most affordable ways to work toward that goal—no new equipment required.
Our takeaway: We've talked with countless customers surprised to learn a simple filter swap could meaningfully improve their home's air turnover. Small change, big impact.
(Source: U.S. EPA / CDC – Preventing the Spread of Respiratory Viruses in Public Indoor Spaces)
Here's the truth most filter companies won't tell you: no single air filter can eliminate every bacterium or virus from your home. Anyone who says otherwise is overselling.
But after more than a decade of building filters in the U.S., talking directly with millions of homeowners, and watching the science evolve—especially through the pandemic years—we can tell you this with confidence: the right filter makes a meaningful, measurable difference.
Bacteria and viruses don't behave the same way in your air:
We've had thousands of conversations with real customers who noticed a difference after upgrading their filter. A few patterns come up again and again:
These aren't outliers. They're the norm.
Most homes are underfiltered. A lot of people are still running MERV 8 filters—or worse, cheap fiberglass panels—because that's what came with the house or was cheapest at the store.
A MERV 8 is better than nothing. But it's leaving a lot of what you actually want to catch right there in your air:
If we could recommend just one thing to every homeowner, it would be this:
It's not complicated. It's not expensive. But it's one of the highest-impact things you can do for your home's air quality, your HVAC system's longevity, and your family's everyday comfort.
We didn't get into this business because air filters are exciting. We got into it because clean air matters—and because we saw a chance to make it easier, more affordable, and more accessible for every household in America.
That mission hasn't changed since we shipped our first filter back in 2013. Everything we've learned since then has only made us more obsessed with getting it right.
Better air isn't a luxury. It's something every home deserves. And we're here to make sure getting there is as simple as possible.
You know how bacteria and viruses behave in your air. You know what your filter can do about it. Now let's put that knowledge to work. These steps take just a few minutes.
Pull out the filter in your HVAC system and look for two things:
Not sure what size you need? Check the dimensions on the frame or use our filter size finder to match your exact fit in seconds.
This is the single upgrade that delivers the most noticeable improvement for the widest range of homes:
Even the best filter stops working when it's clogged, so staying on top of replacements is key. For homes with multiple pets, smokers, or located in high-pollen areas, plan to swap your filter every 30 days. If you have pets, allergy sufferers, or heavy foot traffic, every 60 days is the sweet spot. And for standard households with moderate use, changing your filter every 90 days will keep your air clean and your HVAC running efficiently.
Pro tip from our team: don't rely on memory. Set a reminder—or better yet, let auto-delivery handle it for you.
This is the step that turns good intentions into lasting results:
Want to go deeper? These resources pick up right where this article leaves off:
A: Yes—but they work differently for each.
From our experience, we tell customers the filter isn't chasing individual viruses. It's intercepting the vehicles they ride on.
A: MERV 13 is the recommended starting point for most homes. Here's why:
From our experience: after shipping millions of filters at every MERV level, MERV 13 is where customers consistently report the most noticeable improvement—especially for allergies and respiratory comfort.
A: Yes, for most standard residential systems. A few things to keep in mind:
From our experience: we've shipped MERV 13 filters to millions of homes nationwide. The vast majority of systems handle them without any issues.
A: It depends on your household, but here's a general guide based on what we've seen work best. Homes with multiple pets, smokers, or high pollen exposure should aim to replace their filter every 30 days. If you have pets, allergies, or heavy foot traffic, every 60 days is the sweet spot. For standard households with moderate use, every 90 days will keep your air consistently clean. The key is staying on schedule—because even the best filter stops doing its job once it's clogged.
From our experience: customers who commit to a regular schedule often report lower energy bills alongside better air quality.
A: Start with a MERV 13 filter. Add a purifier if you want extra room-level protection. Here's the difference:
How to think about it:
Upgrade to a MERV 13 filter today and give your home the protection it deserves. Shop MERV 13 filters now and enjoy free shipping, factory-direct pricing, and the convenience of auto-delivery—so clean air is one thing you never have to worry about.
