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When setting up a new air conditioning system, one thing a lot of homeowners forget to consider is the quality of the air blowing through the ducts. Clean, fresh air in your home can help you feel more awake and focused during the day, and unfiltered or dirty air puts you at a higher risk for respiratory conditions. For these reasons, pretty much all HVAC systems these days come with some kind of air filtration capability.


It used to be that you could get away with just placing a filter over the blower in your A/C unit and call it a day, but modern air conditioners have much more advanced options available to choose from. Between all the different kinds of filters, scrubbers, and air purifiers out there, it can be a little difficult to know where to start. If you’re considering adding a new air filtration system to your air conditioner but you’re feeling stuck, just read on and we’ll give you all the details you’ll need to make an informed decision.


Why Clean Air Matters

For most people, especially healthy, active adults, it might seem like overkill to put so much thought into air quality. After all, don’t we all go around breathing unfiltered air every single day? However, medical research has shown that the quality of the air you breathe can have a significant effect on your health, even if you’re otherwise very health-conscious. This is especially true if you live in an urban area, where air pollution is made worse by cars, furnaces, factories, and other manmade polluters. Even rural homeowners are still at risk from natural air pollutants like smoke, dust, mold, and particulates of diseases like norovirus and even Covid-19. Air contaminants don’t just come from outside your house, either. In fact, the EPA estimates that the air inside our homes and businesses is up to five times as unclean as the air outside due to collected dust, skin flakes, chemicals, mold, and pollutants like cigarette smoke. Taking good care of your health means being careful about what you put inside it, whether that’s food or air, so making sure your HVAC system is cleaning the air in your house as it cycles is a smart idea.


For a long time, we thought of poor air quality as primarily a threat to respiratory health. While recent studies have exposed the other health risks connected to low air quality, your lungs are still going to be the greatest beneficiaries of a good air filtration system. This is especially true for children, who are at higher risk of developing respiratory conditions like asthma if the air quality in their homes is poor. If you already have asthma, unfiltered air can increase the chances of having an asthma attack and even make the symptoms more severe. Particulates like dust, mold, and pollen can also make allergy symptoms much more severe unless filtered out by your HVAC system. Air pollution has also been linked to respiratory conditions like chronic bronchitis, and emphysema.


More recent research has shown that the effects of air pollution go beyond your lungs as well. Very fine particulate matter can impair the function of your blood vessels and even your heart. Even worse, exposure to poor quality air can lead to inflammation in the cells of your body which contributes to chronic diseases, strokes, and even some cancers. Because air is so important to every function inside the body, bad or polluted air can cause problems pretty much everywhere.


So are you going to get cancer if you don’t install the right air filter in your HVAC system? No, probably not. But it’s clear that the quality of the air you breathe in can have significant effects on your overall health and the health of your family, so it’s better to be safe than sorry. Even a simple disposable filter inside your air conditioner can make a difference, but if you’re looking for something more powerful, you have a few different options that you can explore.


Air Scrubbers

If you want something a little more heavy-duty than the standard air filter that comes with most HVAC systems, you have two primary options: an air scrubber, or an air purifier. As the name suggests, an air scrubber is designed to clean the air that passes through it, trapping any harmful chemicals or particulates and letting fresh air pass through to the other side. Scrubbers are more powerful than air purifiers, so if you’re looking for a good place to start, this is what we’d suggest. Air scrubbers are also generally simpler and don’t usually involve any chemicals that could be harmful if released into the air, which is why many homeowners feel more comfortable with a scrubber instead of a purifier.


While air scrubbers are mostly used in industrial settings, they’re also popular for household HVAC systems as well. Industrial air scrubbers are designed to remove any potentially dangerous chemicals from the exhaust vented by factories and other industrial buildings. Because these chemicals can be so harmful, industrial scrubbers are typically much more powerful than the ones you can buy for your home. However, the general idea behind the technology remains the same whether you’re installing it in a factory gas flue or the ducts of your HVAC system at home. Scrubbers of all kinds are extremely effective at cleaning the air, generally capturing and removing 99% of all contaminants from the air before it reaches the vents, including dust, mold, pollen, and even microorganisms like bacteria, fungi, and parasites.


Air scrubbers are separated into two categories based on the method they use to filter the air. Dry scrubbers are the cheapest and most common type of scrubber, and more closely resemble a standard filter. They’re generally made up of a few different filters pressed together, each with a different function. Pre-filters are used to capture the largest contaminants, like small objects or large particles of dust. Pre-filtering the biggest objects just makes the primary filter’s job easier. After the pre-filter, dry air scrubbers use another filter treated with materials called sorbents that trap the rest of the contaminants.


Scientifically speaking, a sorbent is any material that collects molecules from another substance through either absorption or adsorption. We don’t need to get too deep into the chemistry here, but different dry scrubbers will use different sorbents to capture any contaminants while allowing the clean air to pass through. Industrial scrubbers, for example, will generally use basic chemicals like an alkaline slurry to keep acids from escaping into the atmosphere. The most common sorbent in household HVAC systems is activated carbon, which is able to filter out most gasses, vapors, and organic chemicals in the air.


Because air scrubbers are so effective in filtering even the smallest particles from the air, they tend to cost a pretty penny. Depending on the kind of scrubber you have installed, putting one in your HVAC system will cost between $1,000 and $3,000, which is a significant chunk of change. However, if you can afford the high cost of installation, we recommend an air scrubber as the most effective way to clean the air in your home.


Wet Air Scrubbers

Rather than using sorbents like carbon to filter the air, wet scrubbers use liquids. While both kinds of air scrubbers are extremely effective, most experts agree that wet scrubbers are the gold standard for cleaning the air. While sorbents use absorption and adsorption to trap molecules and filter the air, wet scrubbers use solvents to dissolve any contaminants. Though wet scrubbers are somewhat more effective than dry scrubbers, you should get essentially the same result with either method. Both wet and dry scrubbers will capture 99% of the particulates in the air, leaving your house with only clean, fresh air to breathe.


Much like dry scrubbers, wet air scrubbers are used in industrial facilities and on construction sites to make sure dangerous chemicals aren’t being released into the atmosphere. Wet scrubbers are extremely versatile, as the chemical composition of the liquid solution inside the scrubber can be changed depending on what needs to be filtered out of the air. For example, a factory that needs to filter acids from ventilation gas to prevent contributing to acid rain would use a caustic solution like sodium hydroxide to dissolve the acids harmlessly and allow the air to escape.


A household air scrubber, however, doesn’t really need anything as complicated as sodium hydroxide. Most wet air scrubbers in HVAC systems just use water for simplicity and versatility’s sake. Not only is water the least expensive and most convenient option, but it’s also an extremely powerful solvent by itself. Water alone is more than enough to filter out any contaminants that might make their way into your house, including dust, pollen, microorganisms, and anything else you might imagine. Much like dry air scrubbers, wet scrubbers also feature a standard HEPA filter to catch anything that made it through the water.


Industrial wet scrubbers will generally use large chambers with a liquid spray that cleans the gas as it passes through, but household ones are a little more straightforward. With an HVAC wet air scrubber, the air conditioner blows air through a filter that’s been saturated with water. The water dissolves a bunch of the particulates that pass through, and everything that escapes the water gets caught in the filter itself. Wet scrubbers give an extra little benefit by also acting as small humidifiers, keeping the air in your ducts from getting too dry, which can be useful in warmer climates.


Both types of air scrubbers are mostly used in industrial or construction settings, making them overkill for the average homeowner. If you’re especially worried about the quality of the air in your house, or you have some extra money you don’t mind spending, then an air scrubber is the best option available for your HVAC system. Otherwise, you might want to look into something a little simpler like an air purifier or solid HEPA filters.


Air Purifiers

While the line between an air scrubber and an air purifier can sometimes be blurred a little, the main difference for our purposes is that a purifier releases chemicals or substances of one kind or another into the air to purify it as it passes through the ducts. This can be done through a wide variety of methods, so “air purifiers” is a pretty loose category. We’ll go over a few of the most common types of air purifiers here so you can get an idea of what’s available when you’re making your decision.


First, you may have seen air purifiers that use ozone to remove contaminants advertised before. These products claim that ozone will create a chemical reaction that purges the air of everything but carbon dioxide, water, and oxygen. However, these claims are not backed up by research, and using an ozone generator to clean your air can actually be harmful to your health. If you’re interested in adding an air purifier to your HVAC system, we absolutely do not recommend an ozone generator. There are plenty of other purification systems that actually work and won’t cause any damage to you or the environment.


One of the more popular air purifiers on the market today is the HVAC ionizer. Ionizers work by releasing clouds of single positive and negative ions into the air in your ducts. These atoms travel through the ducts until they meet contaminants. When positive and negative ions stick to contaminants in the air, they continue to cluster until the charge triggers cell oxidation, destroying the contaminant. The leftover ion clusters can then be easily caught in a HEPA filter, leaving the air free and clear. Ultimately, while an ionizer can certainly contribute to an HVAC filtration system, we don’t recommend using it by itself. Adding a HEPA filter or other secondary purifier is a good idea since the ionization cleaning can be unreliable as a primary filter.


Another popular option is an electrostatic air purifier. With this method, the purifier uses static electricity to positively charge any particulates that pass through it, causing them to stick to the filters in the sides of the purifier. It’s not dissimilar to an ionizer and ultimately has similar results. While the static electricity does cause some contaminants to become trapped in the purifier, studies have shown that this method is still less effective than an air scrubber or even just a standard filter. Electrostatic purifiers are also difficult to clean, and have to be replaced every year or so when the performance starts to dip.


The truth is, most of these gimmicky air purifiers are only partially effective. There’s relatively little data backing up most of the claims made by the manufacturers of these products, and some, like the ozone generator, can actually do more harm than good. With a going rate of up to $500 for air purifiers, we recommend sticking with more tried and true methods like HEPA filters and air scrubbers for your HVAC system. Because HVAC systems are already so expensive to install, there’s no sense in paying extra for something that won’t really work.


HEPA Filters

We’ve talked a bit in this article about HEPA filters, and they’re always a great choice for any HVAC system. HEPA stands for “high-efficiency particulate air,” and it’s a classification of standard cloth filters. If a filter is HEPA-quality, that means it’s strong enough to work in any HVAC system. If you’re not looking to spend enough money to get an air scrubber for your air conditioner, a solid HEPA filter will be just about as good at a fraction of the price. HEPA filters have been used in A/C units for decades, and they’re the standard in air filtration for a reason.


Filters are generally made of spun fiberglass or cloth covered by a cardboard frame. The effectiveness of the filter is going to be based on how well it’s made and what materials it’s made out of. Rather than using complicated chemical reactions to clean the air, a HEPA filter just sits across the blower in your air conditioner and traps contaminants like a net while allowing air to pass through. It’s simple, affordable, and can be just as effective as an air scrubber if you’re buying a filter with a high enough grade.


The efficacy of any given HEPA filter will depend on the materials used and how tightly woven they are. Filters are rated on the minimum efficiency reporting value (or MERV) system. MERV ratings go from 1-16, and the higher the number, the higher the quality. Filters with higher MERV ratings tend to be more expensive, so balancing quality with affordability is a good idea.


When it comes to HVAC systems, you want to avoid any HEPA filter with a MERV rating of five or below. MERV 1-5 filters are extremely basic and won’t provide enough filtration for something as heavy-duty as an air conditioner. For the average residential home, you want to look for a filter of MERV 6-8 at a minimum. Once you get to MERV 9 or above, the filters start to become a lot more expensive. A filter rated MERV 16 can capture microscopic particulates as small as 0.3 microns wide, about 70x smaller than a strand of human hair. A MERV 16 filter can easily run you over $100, but it will filter out well over 99% of contaminants in the air, making it comparable with an air scrubber in terms of efficacy.


The biggest downside of a HEPA filter is that it can sometimes be too effective. A HEPA filter with a high MERV rating can actually restrict airflow through your A/C system, forcing it to work harder and wasting electricity. Before buying a filter of MERV 9 or higher, make sure your HVAC system is actually built to handle a filter that thick. Otherwise, you could end up putting extra strain on the motor as well as causing a spike in your electricity bill. A filter of MERV 6-8 should be more than enough for most homes unless you have an especially powerful air conditioner.


It’s important to keep up on maintenance for your entire HVAC system, but that’s especially true for the air filter. Filters can become dirty after only a month during high-use seasons, so we recommend checking regularly to make sure it’s not clogged. Many HEPA filters are reusable, so all you have to do is give them a quick wash and put them back. Some filters are meant to be disposable and should be replaced entirely after a month or two. Check the packaging on the filter before you buy it so you know how often to replace it.


Even if you buy an air scrubber for your HVAC system, we recommend including a reasonably rated HEPA filter as well. The cloth filter will catch anything that makes it through the scrubber, and the two systems working together will provide the best results in terms of air quality.


While doing your own research is important, it’s also a good idea to check with your preferred HVAC installation company before deciding on a filtration system. They may have insight that you can’t find on the internet, or information about your specific air conditioner that can affect your decision. If you’re in Sonoma, Napa, or Marin counties and you have questions about HVAC air filtration, or you’re interested in installing a new air filter, feel free to give Valley Comfort Heating & Air a call at (707) 664-7201. We’re more than happy to answer any questions you might have and help you through the process of deciding on a filter, as well as installing it for you. We can also do an indoor air quality test if you’re worried about the efficacy of your current filtration system.


Valley Comfort Heating & Air offers testing and HVAC installation in Calistoga, Healdsburg, Napa, Rohnert Park, Santa Rosa, St. Helena, and Windsor.