What do air filters do, and how does an air filter work? The idea seems pretty simple, but purifying the air can be a somewhat complex task considering there are 60+ sources of indoor air pollution. Not to mention the hundreds of products that can release volatile organic compounds (VOCs) into the air.
An air filter clearly serves a purpose, but does every home need one? The short answer is yes! But, read on because this guide will give you more information about what air filters are, why they are used, and why every home with an HVAC system can benefit from having them.
Let’s start with the basics by defining what an air filter is. An air filter is essentially a screen that fits into a compartment of the HVAC system to clean the air as it circulates through a home.
Air filters are an aftermarket product with a longevity that typically spans 1-6 months for disposable filters. Washable air filters can last up to five years.
What does an air filter do in your house once it’s installed? The primary air filter purpose is cleaning the air inside so it’s healthier to breathe. You may not realize that many homes have air quality that is worse than outside, and your home could be one of them. If you don’t have proper ventilation and air filters for purification contaminants can build up inside.
Air filters are also a part of the overall HVAC system. They serve as a first line of defense that protect HVAC components from contaminants.
What air filters are made of can influence whether they have a specialized purpose. For example, air filters with carbon are particularly good at removing odors from the air.
Understanding how air filters work can help you decide which filter is best for a specific purpose. All air filters work in a similar fashion:
Where air filters differ most is the media that is used. Filter media quality and quantity influences the size of air particles that can be captured, how they are captured and airflow through the system.
People put a lot of emphasis on the Minimum Efficiency Reporting Value (MERV). The MERV rating is important beyond indicating how well the filter purifies the air. It can also affect airflow, which has a negative impact on the HVAC equipment, energy efficiency and your comfort.
MERV ratings range from 1 (least efficient) to 20 (most efficient). Air filters with a MERV rating of 14 or higher capture more particulates but they also restrict the airflow more and get clogged faster.
Read More: All About MERV Ratings
If a primary air filter function is to clean the air, is it necessary to use one in a home with good air quality? Do air filters make a difference if the air is healthy? Do allergen furnace filters work well enough to eliminate the use of an air purifier?
The short answer is yes, because air filters don’t just clean the air effectively. They also protect your HVAC equipment.
Air filters keep debris and air particles out of sensitive components. Two places where dust and dirt could accumulate are the duct system and air handler. The debris will build up over time creating a variety of issues, along with polluting the air inside.
Do you like wasting energy and paying more than you need to heat and cool your home? If the answer is no, then you’ll want to replace your air filters regularly.
With less dirt and debris in the system, HVAC equipment runs more efficiently. The opposite is true if you have no air filter or the air filter is so dirty it’s restricting airflow. When that happens parts like the fan motor will have to work harder, which means more electricity is consumed. The fan motor is also more likely to need repair.
Even if you’re lucky enough to have great air quality inside without an air filter, your HVAC equipment still needs that layer of protection to work efficiently.
Find the best air filters for your home - search by MERV rating, media type or size
An HVAC air filter works by capturing and removing various airborne particles and contaminants from the air circulating through your heating, ventilation, and air conditioning (HVAC) system. The filter traps dust, pollen, pet dander, mold spores, and other pollutants, preventing them from recirculating into your living spaces.
Having a functioning HVAC air filter is crucial for maintaining indoor air quality. It helps to remove allergens, pollutants, and particles from the air, which can enhance respiratory health and reduce allergic reactions. Additionally, a clean filter ensures that the HVAC system operates efficiently, preventing it from becoming clogged and potentially damaging the system.
The frequency of changing your HVAC air filter depends on various factors, including the type of filter, the level of pollutants in your environment, and the manufacturer's recommendations. As a general guideline, it is advisable to check your filter at least once a month and replace it when it appears dirty or clogged. Some filters may need replacement every three months, while others, such as high-efficiency filters, may last up to six months.
A dirty air filter can hinder the airflow in your HVAC system, causing it to work harder to circulate air. This extra strain can lead to reduced energy efficiency, higher utility bills, and potentially even damage to the system. Additionally, a clogged filter can allow dust and debris to accumulate on the system's components, decreasing its lifespan and requiring more frequent maintenance.
Yes, there are different types of HVAC air filters available on the market. The most common types include fiberglass filters, pleated filters, electrostatic filters, and high-efficiency particulate air (HEPA) filters. Each type has its own filtration capabilities, lifespan, and price range. It's essential to choose a filter that suits your specific needs and consult the manufacturer's guidelines for your HVAC system.
The Minimum Efficiency Reporting Value (MERV) rating is a scale that measures the effectiveness of an air filter. While a higher MERV rating typically indicates better filtration and the ability to capture smaller particles, it may not always be necessary for residential HVAC systems. Higher MERV-rated filters may also restrict airflow, which can strain the system. It is advisable to consult the HVAC manufacturer's recommendations or seek professional advice when choosing the appropriate MERV rating for your specific system.
Everyone wants clean water — but the truth is that even water in nature isn’t technically “pure.” That’s why we humans have been improving the taste, odor and appearance of our drinking water since at least 4,000 B.C.
Of course, our methods — and the research that guides them — have advanced. Today’s water filtration systems work through sophisticated physical or chemical processes that address different contaminants in distinct ways. Some can even help control your water’s pH.
Read on to see how water filters work, what they do and why it matters.
From the simplest water pitcher filter to the most comprehensive reverse osmosis (RO) or whole home system, water filtration is all around us. However, different methods have different results — and that’s an important distinction if you’re looking to solve a particular water quality problem.
Here are some of the most common water filtration processes and how they work:
Reverse osmosis is based on a naturally occurring process responsible for helping plants absorb water from soil. This is called “osmosis,” and it involves a semipermeable membrane separating two amounts of fluid. One side has a higher concentration of solutes than the other. To create a sort of equilibrium, fluid with fewer solutes tries to flow to the other side, moving through the membrane along the way.
In reverse osmosis filtration, this process happens backward: An outside force or pressure causes the fluid to move in the opposite direction, or against the “concentration gradient.” As this occurs, solutes like salt are left on one side of the membrane and filtered water flows into the other. That’s why RO is often used for seawater desalination as well as everyday filtration.
It’s important to keep in mind that the reverse osmosis process itself is often only one part of what’s actually happening in an RO drinking water filtration system. The best solutions combine RO with other filters and processes to catch different kinds, sizes and amounts of contaminants.* Some even have optional filter cartridges that put you in control of your water’s pH.
In this type of filtration, carbon or activated carbon forms the basis for a process called adsorption, not to be confused with absorption:
That one letter makes a big difference. Because carbon filtration uses adsorption instead of absorption, certain tiny materials stick to the carbon while the rest of the water flows through. This solution is a good fit for chlorine, sediment, certain organic compounds and some other contaminants, but it may not catch other materials that could potentially cause aesthetic and health concerns.
Activated alumina (AA) is a porous material made from aluminum oxide. An AA water filter works in much the same way as carbon filtration; however, it’s perhaps a bit more complicated — and that means its benefits can be a bit less reliable, too. For example, while AA filters are often a good fit for particular water quality problems such as fluoride or arsenic, the effectiveness of the filtration process relies on the AA material itself, plus the pH and material makeup of your water supply. Some people are also concerned that the main component of AA, aluminum, may leach into the water under certain circumstances.
Mesh filtration is perhaps the easiest to picture. It relies on tightly woven layers of wire cloth, creating a sort of trap that’s generally most effective for sediments such as sand and dirt. Mesh filtration on its own can’t catch certain contaminants or impurities, particularly those that have dissolved in the water.
You may notice that this process is somewhat similar to reverse osmosis. While it’s true that many kinds of filtration rely on the same basic concepts, keep in mind that RO membranes are designed differently and often installed in systems with other filter media.
Although a simple water pitcher filter may rely on just one kind of filtration, some of the best systems unite different solutions for a more comprehensive, complementary treatment process. RO is one example of this, but a more familiar application may already be connected to your house: treated city water.
Cities have varying approaches to water treatment, sometimes because relevant governing bodies have established different water quality guidelines (like Water Quality Standards in the U.S. and the Guidelines for Canadian Drinking Water Quality in Canada). However, many cities use this combination of filtration methods:
Remember, private wells don’t have this kind of water treatment, which is why fluoride and chlorine issues are less common there while others, like high iron or hydrogen chloride levels, are more common. That’s not to say that filtration is only for wells, though; treated city water can still have problems from issues such as hard water or contaminants that are not yet federally regulated, like PFAS in water.
In many ways, filtration is a step you add to the water cycle. Think about the way water moves through ecosystems: It exists as precipitation, snowmelt and runoff and can gather in lakes, rivers, aquifers and more. In all of these stages and locations, it has plenty of opportunities to pick up minerals, sediment and other materials — and in nature, that’s not necessarily bad. It only becomes a problem when that unfiltered water ends up in your glass.
Filtration is able to address these concerns from any source or water system. After all, it’s not just nature that impacts your water quality; other elements — such as corrosion in your home’s piping or chlorine added to municipal water — can also play a role. That’s why it’s helpful to think of filtration as the last step of your water’s journey before it ends up at your tap.
Broadly speaking, a water filter’s job is to address and reduce a wide range of potential problems. Depending on the type of filter, these may include:
How exactly a filtration system achieves this depends on its size, structure and complexity — but the goals are generally similar:
Filtration and softening aren’t interchangeable. The former addresses specific contaminants and water quality issues based on the filtration media or mechanism, and it has benefits such as clearer water and reduced taste issues. The latter removes different materials — like the calcium and magnesium that cause hard water — using resin beads and a saltwater “recharge” process that isn’t part of filtration. Softening doesn’t address taste, odor and appearance issues, but it can help solve hard water problems such as mineral deposits, spotty dishes, dry skin, brittle hair and more.
It’s important to note that filtration and purification aren’t the same thing, especially when it comes to at-home water treatment. Generally speaking, purification is a more involved process that makes water usable for medical, industrial and other purposes. Household tap water for drinking, cleaning, cooking and bathing is usually well-suited for regular filtration — as long as you choose the right filtration system, that is.
As you research house filter options, you’ll quickly notice that there are two primary types of filtration: physical and chemical. These can differ widely — not just in size, price and functionality, but also in comprehensiveness. That’s why it’s helpful to understand the basic mechanics of different filtration types and what they do in practice.
Physical filtration uses a physical barrier to block, trap or catch certain solid debris. It’s the kind of water treatment early civilizations likely used, although in a much simpler form than today’s filters, and you can see it for yourself: Just find a muddy river, dig a hole deeper than the water level and watch cleaner water filter up through the sand or dirt.
To get the job done, a physical filtration system needs certain components:
The biggest difference in chemical filtration is that it doesn’t use the same kind of barrier. Instead, it relies on filtration media — that is, an active material that attracts or otherwise traps some contaminants through chemical interactions. For example, in a carbon or activated carbon filter, the medium traps or “adsolves” dissolved materials as they pass through, thereby reducing their presence in the water supply.
Chemical filtration systems need many of the same components as their physical filtration counterparts. However, because each chemical medium type only reacts to or with certain contaminants, these systems may not be as comprehensive on their own.
Now that you understand how water filters work, it’s time to choose one that fits your needs. However, that may be easier said than done. That’s because some contaminated water problems can’t be seen, smelled or tasted — and other issues, such as discoloration or bad odors, can have multiple causes.
To ensure you get the right filtration solution for the right purpose, it’s smart to begin with a professional water test. Your local water expert will test for chlorine, iron, total dissolved solids (TDS) and more — and in about 30 minutes, you’ll have the answers you need. You’ll even get personalized recommendations to help you choose the best house water filter system.
Ready to get started? Schedule your free, in-home water test and consultation.