The Importance of Standalone Air Filters
A good air filter is one of the easiest and most reliable ways to improve your air quality. We recommend them to almost everyone we work with.
Why? Because indoor air is a complex mix of pollutants: outdoor pollution, off-gassing from furniture, cleaning products, cooking fumes, and more. Among these, ultrafine particles, especially those smaller than 2.5 microns (PM2.5), are particularly dangerous as they can penetrate deep into your lungs and even enter your bloodstream. These particles are linked to respiratory and cardiovascular problems, making effective filtration so important for your health.
Addressing pollution at its source is ideal, but it isn’t always practical, or even possible. Think of air like water: when you’re concerned about contaminants in your drinking water, you don’t fix the city’s treatment plant; you install a filter in your home. Air works the same way.
Even if you have an HVAC filter (that square or rectangular filter you put in your intake vents), we still recommend standalone air purifiers. In fact, counterintuitively, we recommend you use less effective HVAC filters: around MERV 8 instead of a higher-efficacy MERV 13 or above filter.
Why is that? Because the higher the HVAC filter grade, the lower your rate of airflow in your house will be. The most effective way to filter your air is with high throughput through the HVAC system, circulating air quickly, and good standalone purifiers in the rooms.
And anyway, most HVAC filters are designed to protect your equipment, not your lungs. They catch larger particles but miss the smaller particles that are more of a health concern.
The ideal setup is a lower MERV filter (like MERV 8) in your HVAC to maintain airflow, plus dedicated standalone air purifiers across the home. If you can’t get standalone units, using a MERV 13 filter in your HVAC helps, but may strain your systems.
How Do Air Filters Work?
High-quality air filters use a combination of physical and chemical processes to clean your air.
HEPA Filters
Most air purifiers contain HEPA filters, which use a dense mat of fibers to physically trap particles as air passes through.
But here’s something interesting: filters are highly effective at capturing both very large particles (like dust and pollen) and extremely tiny ones (like smoke). But they are least effective at capturing particles in the “middle” size range, typically around 0.1 to 0.3 microns. This is called the “most penetrating particle size” (MPPS).
This is because large particles get stuck in the filter fibers, and smaller particles move erratically (Brownian motion) and collide with the fibers. But middle-sized particles are small enough to slip through gaps, yet not so small that they bounce around randomly.
Even so, true HEPA filters remove at least 99.97% of these “most penetrating” particles, and even more of other sizes.
Activated Carbon Filters
These work differently. Instead of trapping particles, they adsorb gases and odors (like VOCs from cleaning products or off-gassing furniture) onto the surface of millions of microscopic pores in the carbon. The amount of carbon varies dramatically between units, from thin pre-filter sheets to several pounds of pellets. More carbon means better VOC removal, so it’s something to look out for (more on this below).
Other Technologies
Some filters use UV or ionization (though these are less reliable and can sometimes create unwanted byproducts like ozone, and have less data behind their efficacy than HEPA and carbon filtration).
How to Choose an Air Filter
Step 1: Ensure Sufficient CADR for Your Space
When choosing an air filter, by far the most important factor is the throughput, typically listed as CADR (Clean Air Delivery Rate). This tells you how much clean air the unit actually delivers, which matters far more than any other marketing claims about “advanced technology” or “hospital-grade” filtration. Any HEPA filter can filter 99.97% of even the particle size it is worst at, so the thing you really care about is how much air it can push through that filter.
Here’s a simple rule: multiply the CADR by 1.5 to roughly get the coverage area in square feet. For example, a unit with a CADR of 200 is good for a ~300 sq ft room.
Step 2: Choose the Right Filter Technology for Your Needs
For general purposes, look for True HEPA + activated carbon. This combination will effectively handle both particles and gases/odors.
If VOCs are a concern, or if residents have chemical sensitivities, then prioritize filters with substantial carbon, as thin carbon pre-filters won’t cut it.
Step 3: Consider Practical Factors
Noise level: For bedrooms, we typically recommend units under 50 dB on medium speed.
Maintenance: Check the replacement schedule and cost of HEPA and carbon filters. These can vary dramatically.
Design: We know many purifiers look clunky, but well-designed models exist, so you can definitely find an effective model that still suits your space.
The Optimal Set-up for Your Home
To make things simple, we’ve put together a tool where you can input your home’s square footage, ceiling height, carbon filtration priority (for VOC reduction) and some other factors to get a personalized recommendation on the optimal number and types of filters your home needs.
This tool will give you an optimal recommendation based on your home size and preferences. While it may suggest more filtration than you expected, it’s designed for full coverage. That said, making small changes will help. Just do as much as you can, and start where it’s most impactful.
How to Use Your Air Filter Effectively
Placement Matters
Position your air filter at least a few feet from walls to ensure proper airflow circulation. Also, prioritize using them in high-use areas, such as bedrooms.
Run it 24/7 at the Highest Comfortable Speed (Not on Auto)
Air purifiers set to “auto” mode are often triggered only when particulate matter reaches certain concentrations of certain particle sizes, which means smaller particles can accumulate in the meantime. We recommend running the air purifiers continuously at the highest setting that is comfortable in terms of noise.
Set Reminders for Filter Changes
To ensure optimal performance, set calendar alerts for filter maintenance. HEPA filters typically require annual replacement, whereas the lifespan of carbon filters can vary significantly depending on the model.
A Pro Tip for Travelers: The Wearable Filter
We’re often asked about air quality while traveling. Our team has been impressed with the Respiray, a wearable air filter.
While it does look ridiculous, it’s truly great for flights and other places where you’re affected by someone’s cologne or perfume. Most people just assume you have a VR headset or weird glasses case around your neck. We highly recommend it for anyone with chemical sensitivities who travels frequently.
So far this guide has covered particle filtration. VOCs need a different approach.
Exactly How to Filter Out VOCs in Your Air
A good HEPA air purifier handles one side of air quality well: particulate matter like dust, pollen, pet dander, and smoke. But VOCs pass straight through HEPA filters as if they weren’t there.
VOCs are gases that can be released by materials in your home. They can off-gas from furniture, flooring, cabinetry, paint, cleaning products, mattresses, and dozens of other sources. Some you can smell, like new furniture or fresh paint. Many you can’t. They can off-gas for weeks, months, or in some cases years, and they’ve been linked to respiratory irritation, headaches, and longer-term health effects.
There is no clear benchmark to compare how effective air purifiers are at VOC removal, no standardized testing, and far fewer trustworthy options than there are for particle filtration.
The short version
HEPA filters catch particles. VOCs are gases; they pass right through HEPA like air through a screen door. Removing gases requires activated carbon, which traps gas molecules onto a porous surface. More carbon means more capacity before it saturates.
Every HEPA purifier we recommend for particles includes a thin carbon pre-filter. That handles light odors, cooking smells, mild pet odor, and is fine for most people. But a thin carbon sheet weighing a fraction of a pound saturates fast and isn’t built for serious chemical loads.
For real VOC removal you need a thick bed of granular activated carbon: 10 to 20+ lbs for serious concerns. That’s a fundamentally different product.
Carbon weight isn’t everything
Standard activated carbon handles a broad range of VOCs. But some pollutants, formaldehyde especially, are poorly captured by plain carbon. Potassium permanganate or potassium iodide impregnated carbon is significantly more effective for aldehydes. Other chemical families benefit from other specialty blends.
Several manufacturers (such as AllerAir and Airpura) let you swap carbon canisters or upgrade to different formulations. This matters if you know what you’re dealing with. If you don’t, standard activated carbon is a good starting point.
Figuring out the right carbon media requires understanding what’s actually in your air, and that depends on building materials, furnishings, location, and activities. Lightwork can help with that assessment if you want a recommendation tailored to your home.
Why these are hard to compare
These aren’t commodity products with standardized specs. Each manufacturer takes a different approach: different carbon media blends target different chemicals, some units use multiple filtration stages while others are single-stage, some integrate real HEPA alongside the carbon bed while others are carbon-only.
Even “carbon weight” isn’t a clean comparison. Bed depth, packing density, and granule size all affect performance at the same weight. And airflow numbers are typically free-flow ratings that don’t account for resistance from a loaded filter.
The right choice depends on what’s actually in your air.
A couple caveats
These are not quiet machines. Pushing air through 15 to 20 lbs of packed carbon takes a serious fan. None of these will disappear into the background the way a good HEPA purifier on low can. If noise matters to you, plan to run them in a room you’re not sleeping in, or cycle them on while you’re out.
Use two purifiers to cover both particulate matter and VOCs, not one. Most “2-in-1” purifiers use a token amount of carbon that saturates within weeks. Some carbon units include real HEPA alongside heavy carbon beds, which is genuinely useful. But the best setup for comprehensive air quality is usually a dedicated HEPA purifier for particles and a dedicated carbon unit for gases. Each does its job without compromising the other.