20 Questions About Air Purifiers

what size air purifier do I need

20 Questions About Air Purifiers

There are many misconceptions about what an air purifier does and how it works. We’ve put together a list of common questions about air purifiers and will try to address some of the mistaken beliefs that many folks have about these important home appliances.

What is an air purifier?

Air purifiers are exactly what their name implies. In the most basic terms, they purify the air of the space where they are located. Purifying the air refers to removing contaminates such as dust, pollen, mold, bacteria, viruses, pet dander, odors, and other chemical substances from the air. All of these things can irritate the respiratory system, aggravate allergies and asthma, and lead to more serious medical conditions such as heart and lung disease, nervous system disorders, and various cancers.

Why do I need an air purifier?

This is probably a question you’ve been asking yourself since you are here, reading this article. Well, there are a couple of reasons that most people should consider using air purifiers in their homes. First, the air inside your home is likely 2 to 5 times dirtier than the air outside your home. That may come to a shock to most folks but it is true for most homes.

The reason that the air in your home is so dirty is because of the way homes are being constructed these days. They are all being built with energy efficiency in mind so, building envelopes are much more “tighter” to prevent drafts. A drafty home wastes much more energy than a home that is built very tight and draft resistant.

A newer, draft resistant home does not have as much air changeover (ventilation) as older homes. Less ventilation means the pollutants inside your home are trapped there, with no way to get out. They build up inside your home, creating a very poor indoor air quality.

The second reason that you should probably consider putting an air purifier in your home is the fact that we spend so much more time indoors than we used to. It is estimated that most folks spend up to 90% of their time indoors. Between the dirty air in your home, to the dirty air in your car, and the dirty air in your office, you are experiencing chronic exposure to unhealthy air almost continuously. This can lead to a large number of health issues ranging from allergy symptoms to cancer.

How does an air purifier work?

Most air purifiers pull in air from your home and move it through a filter, or series of filters. Particulate matter, VOCs, and odors are removed and the purified air is recycled back into your home. This process repeats indefinitely with the air getting progressively cleaner with each pass through the appliance.

Other purifiers put charged particles into the air called ions. These ions bond with particulate matter floating in the air. When this happens, the combined particle becomes heavier than air and falls down to a surface in the home.

Still others utilize charged plates inside the purifier that attract the particles as they pass through in the airstream. A pre-filter of some sort can also be incorporated in this type of air purifier.

Finally, some air purifiers use an Ultraviolet light (UV) to kill mold spores, viruses, bacteria, and other pathogens. As these dangerous microbes pass through the UV light they are essentially destroyed.

Air purifier questions answered

What are the different types of air purifiers?

There are several different types of air purifiers available to consumers today. Each one capable of removing different types of air contaminates from your air with varying degrees of efficiency. Let’s take a quick look at the most common air purifiers available on the market today.

HEPA Filtration Air Purifier

HEPA stands for High Efficiency Particulate Air and is the gold standard as far as air purifiers go. These units can filter out up to 99.97% of all particulate matter floating around in your air that is 0.3 micron in size and greater. This includes dust and dirt, dust mites and dust mite debris, pollen, mold spores, smoke particles, and some bacteria and viruses.  

To give you some idea on how big a micron is, consider that the human hair is about 70 microns or so in diameter and the best human eyes can just detect debris floating in the air through a beam of sunlight down to about 30 microns in size.Pollen, mold, dust are some of the pollutants air purifiers clean from the air

HEPA filtration air purifiers will not remove most VOCs (Volatile Organic Compounds) from the air unless they have bonded with water vapor molecules in the air. To remove these dangerous substances, your air purifier needs to be equipped with an activated carbon filter element. Activated carbon is a very porous material which has a massive surface area. Think about a sponge and its ability to soak up large amounts of liquid. It does this by trapping water in the many tiny nooks and crannies of the sponge. The same principle applies with VOC molecules. They become trapped as they pass through the activated carbon filter, thus effectively removing them from the air.

Electrostatic Air Purifiers

These purifiers use electrically charged plates inside the unit to attract particulate matter to these plates where they stay bonded to the surface until they are removed by cleaning. Electrostatic air purifiers are good for removing most types of air pollutants other than odor causing VOCs however, their first pass efficiency rating is lower than that of HEPA air purifiers. First pass efficiency just refers to how much particulate is removed in one cycle through the filter unit. It is a measure of how fast your air purifier can completely clean the air in your room.

These systems must be cleaned on a regular basis to keep them running at peak efficiency. This may not seem like a big deal but removing the charging plates in some purifiers can be quite a process. Cleaning the plates, particularly if there is considerable build-up, could also be difficult. Also, electrostatic air purifiers can emit some ozone into the air which can be irritating to some individuals.

Ionic Air Purifiers

Ionic air purifiers do not normally utilize a fan to move air through the unit but rather, they emit a stream of negative ions into the air that bind with dust and other pollutants in your air. As the negative ion bonds with positively charged particulate matter such as dust, pollen, mold spores, bacteria, and viruses. The negative ions can bond with many particles, causing the resultant charged particle to become too heavy to remain airborne.

These heavier-than-air particles then fall from the air, attaching to various surfaces of your home. Because they are charged, they can attach to just about any surface including walls, tv screens, blinds, etc.

Although Ionic air purifiers are similar to electrostatic purifiers in that they apply an electrical charge to the particulate matter in the air, they do have one major difference. Ionic air purifiers do not actually remove pollutants from your home. They remove particulate from the air but the particles still remain in your home, free to become airborne again if not removed via cleaning.

Ultraviolet Air Purifiers

Ultraviolet, or UV for short, means beyond violet. In regards to the visible light spectrum, violet light is the highest frequency of visible light. UV lights produce a frequency of light that is higher than violet and is mostly invisible to humans. UV radiation is responsible for sunburns from over-exposure to the sun’s rays and it is also responsible for most skin cancers as well.

Certain bands of UV light, specifically UV-C  are highly effective at killing microbes and for that reason it is used in many sterilization and disinfection processes. Hospitals and clinics have used UV light for this reason for many years.

Water utilities use some form of UV sterilization for their municipal water supply systems. Food manufacturers utilize UV rays to kill germs in food to prevent customers from getting sick due to microbial contamination.

HVAC system manufacturers and others involved with indoor air quality and purification have started to realize the benefits of using UV lights as an effective means to kill microbes such as bacteria, mold spores, and viruses in the air.

UV air purifiers can either installed as part of your home’s central AC system or can also be found as portable models that can be moved around the home. They are quite effective at removing microbes from the air but do little for all the other contaminants floating around in your air.

Most portable units will usually have a HEPA filter element and UV light source built into one device. As the purifier filter cleans the air of larger particulate matter, viruses, bacteria, and mold that gets through will be neutralized by the UV light.

Apart from having to replace the HEPA filter when it gets saturated, the UV light bulb will have to be replaced at some point. Usually about once a year is the recommended interval for replacing the UV light bulb with some manufacturers.

Ozone Generating Air Purifiers

Ozone is the largest component of air pollution. Ozone is highly irritable to the respiratory system in even small amounts. It has disinfecting properties but is not recommended as an air purifier because the level of ozone that is required to effectively kill germs and other pollutants in the air is unsafe for humans. It is best to avoid using an ozone generating purifier.

Which air purifier should I choose?

With all the available options for air purifiers, it may be difficult to make a choice as to which one is right for you. The best overall option, for most homeowners, is the HEPA filtration air purifier with activated carbon elements. This purifier can remove particulate matter and VOCs from your air very effectively and can even remove those really small contaminants such as bacteria, mold spores, and some viruses.

Any of the air purifiers we have discussed will do a good job of removing particles from the air but, overall, the best choice is the HEPA purifier with activated carbon. These units come in various sizes so check out this article on picking the right size air purifier for your home.

What is a HEPA filter?

HEPA stands for High Efficiency Particulate Air. It is a standard of particulate filtration. These mechanical type filters are made of tightly woven filaments. The spaces in between these filters is what allows air to pass through while trapping particles. Smaller spaces between filaments indicates a tighter weave that is able to trap smaller particles.Air purifier filter   

To be classified as a true HEPA, a filter must be capable of trapping and removing at least 99.97% of particulate matter from the airstream as small as 0.3 micron in size. Air purifiers that remove particles that are this small is of utmost importance because it is these tiny particles that are the most dangerous to human health.

HEPA filters typically have a MERV rating of between 17 and 20. Minimum Efficiency Reporting Values, or MERV ratings indicate how efficient the filter is a removing particles of a certain size from the air. For comparison, the filter for your home HVAC system is probably a MERV 5 to 8.

What to know more about MERV ratings?

How often does a HEPA filter need to be replaced?

The answer to this question is reliant upon so many variables that it would be impossible to give an accurate timeframe. It all comes down to filter saturation. Saturation is simply the point at which the amount of dirt and other particulate that has collected in the filter is so great that it has reduced the airflow to such a point as to render the filter ineffective at removing particulates from the air.

This is going to be a trial and error situation for most folks. If your air is really dirty, if a smoker lives in the home, if you have pets, can all contribute to short filter lifetimes. However, for those folks that live in a relatively clean home with no pets and no smokers, your filter could go much longer than others.

I’ve seen recommendations anywhere from once a month to once a year. Follow your manufacturer’s initial recommendations (about every 4 months) but be prepared to make changes to that schedule as particle load dictates.

Do air purifiers make a lot of noise?

In short, most air purifiers do not make a lot of noise when compared to other sources of sound in our homes. Consider this, the average air purifier noise output falls somewhere between a whispered conversation and the sound of your refrigerator running.

A major factor in the amount of noise an air purifier will produce is the type of filtration the purifier uses. HEPA filtration air purifiers generally create the most noise because of the fan that is used to pull air into the unit. Fan speed is selectable on most units so it makes sense that higher fan speeds will result in higher noise level.do air purifiers make a lot of noise

Ionic air purifiers do not generally use fans and therefore are almost completely silent. Another low noise purifer is the electrostatic purifier. It moves air via a fan but because it does not have to pull air through a filter element, tends to be slower speeds and much less noise.

Another factor in determining how much noise an air purifier will produce is its placement in the home. Rooms with solid flooring and few furnishings will tend to let the noise from the air purifier bounce around more than would a carpeted room with furniture and draperies to help absorb noise.

You can check out the complete article on air purifier noise here.

How much electricity do air purifiers use?

Air purifiers do not use a great deal of electricity. As a matter of fact, they fall far short of most of the appliances you have in your home and use on a daily basis. The average air purifier will consume about $6 to $12 of electricity per month, depending on the cost of your electricity.

Most air purifiers use between 50 and 100 watts of power per hour. Compare that to a medium flat screen TV that uses 75 to 200 watts, a refrigerator that uses 250 to 400 watts, and an AC unit that uses between 600 to 1000 watts per hour.

It is quite simple to figure out what your air purifier will cost to operate by using a simple formula. You will need to know what your electricity costs in cents per kilowatt hour. This number is easy to calculate. Look at your last electric bill. Read the total kilowatt hours used for the month. Take the total bill and divide by the total kilowatt hours used. This will give you your electricity cost in cents per kilowatt hour.

You will then need to determine the wattage rating for the air purifier that you are wondering about. This number should be listed in the machine’s specifications.

Next, we will take the wattage of the unit and multiply it by 24. Take this number and divide it by 1000. The result will be the total number of kilowatts used by the device in one day. Next, multiply this result by the cost per kilowatt hour you calculated from your electric bill and there you go…the price per day that this air purifier is costing you to run. Finally, multiply the costs per day times 30 days to figure out how much this unit is adding to your total electric bill each month.

More information here.

Should air purifiers run all the time?

As a general rule, yes, air purifiers should be running continuously throughout the day. When first placed into a room, run your purifier at its highest fan speed to quickly clean the air. After your unit has had time to remove most of the pollutants from the room’s air, you should be able to reduce the fan speed to maintain the level of indoor air quality at a good level.questions about air purifiers and can they run all the time

However, by turning off the unit, the air in the room will return to the original condition, sometimes quite quickly. By keeping the unit running all the time, the air quality will be maintained instead of shifting from good to bad and back again. An air purifier running at a low speed should be able to keep up with the amount of pollutants being generated in the room by the outgassing of VOCs and the everyday activities of people and pets in that room.

Where should I put my air purifier?

One thing to keep in mind about portable air purifiers is that they are not designed to clean the air in your whole home. Only units incorporated into the design of your home’s HVAC unit can do that. You are going to want to put your air purifier in rooms where they will be the most beneficial, i.e. rooms where you and your family spend the most time.

When shopping for an air purifier, you need to have in mind what rooms you are most concerned about. Usually, the bedroom is one area where you will want to keep the air as clean as possible. It is the room where you spend the most time. Generally, you can opt for a smaller, quieter unit for this room as they tend to be a smaller size as compared to other areas of the home.

Using an air purifier in the kitchen is a great idea as well. Cooking can really do a number on indoor air quality. Check out this article that goes into depth about cooking and indoor air quality.

Air purifiers are sized by what square footage they can handle. Read this article on sizing an air purifier for your requirements here.

How do I know if my air purifier is working?

Obviously, you’ve purchased an air purifier for some specific reason. Maybe, like me you suffer from sinus problems, you might have allergies or asthma and feel like your home’s air may be aggravating your condition.

Give your new purifier time to work. After of couple of days, you should start to experience some relief from these conditions, if poor indoor air quality was indeed the cause of them in the first place. In any case, you should start to notice that the room just feels cleaner, less dense, and easier to breathe.

Another way to tell if your air purifier is working is to take a peek at the filter. You will start to see all the gunk your unit is cleaning from the air start to build up on the filter.

Do air purifiers dry out the air?

Despite what some believe, air purifiers do not remove moisture from the air. They simply do not have any means of removing this moisture and dealing with it. Air purifiers trap particles and VOCs in their filter elements. Any moisture that is temporarily trapped will soon find its way back into your home’s air.

To control your home’s humidity levels, humidifiers and dehumidifiers would need to be used. Humidity most often becomes an air quality issue when moisture levels are high. Humidity levels of 35% to 50% are ideal for most homes. Anything higher encourages mold growth in the home. Higher humidity levels also aid dust mite populations and encourages other pest infestations as well.

Take a look at all the benefits of using a dehumidifier in your home here.

Can air purifiers cure my allergies?

questions about air purifiers and allergies

Air purifiers cannot cure your allergies, nor can it cure asthma or any other health issue. They can, however, remove dust, pollen, and molds that can aggravate these conditions. Good indoor air quality is beneficial to the entire family, whether or not they currently suffer from these conditions, and can prevent future health issues due to bad air.

Can air purifiers remove smoke smell?

Using a HEPA filtration air purifier with activated carbon filters will help to remove smoke and VOCs found in smoke. A good air purifier can go a long way to removing a smoke smell from your home but it, alone, cannot remove everything.

With smoke, and cigarette smoke in particular, the tiny particles and chemical compounds that make up smoke can stick to all types of surfaces. Furniture, drapes, wallcoverings, all need to be cleaned to completely remove a smoke smell from your home.

You can find out more information on removing smoke from your home in this article.

Do air purifiers get rid of dust mites?

Simple answer, no. You can never really get rid of dust mites but you can control them. Air purifiers do remove dust mites and dust mite debris from the air but do nothing for the dust mites that are living in the carpet, bedding, drapes, and other damp areas of your home.

Dust mites feed on the dead skin cells of humans and of pets (pet dander). Keeping your home vacuumed regularly, cleaning bedding routinely, keeping pets groomed and bathed, and controlling humidity levels, are some ways to control dust mites in your home.

This is a good article on keep dust levels low in your home.

Are air purifiers bad for houseplants?

No, air purifiers are not bad for house plants. You home air purifier simply removes particulate matter and other contaminates from the air. House plants use a process call photosynthesis to turn Carbon Dioxide and water vapor in your home’s air into Oxygen and other useful compounds. The two processes are not related and thus an air purifier will not affect house plants in any way.

Having indoor plants creates a comforting home atmosphere for some folks and plants do manage to provide some air purification benefits as well. You do not have to worry about using your air purifier in rooms with houseplants. The two are perfectly compatible. What to know more about this subject? Check out this article.

Can air purifiers remove mold?

Again, a good air purifier with HEPA filtration can remove most mold spores from the air but it cannot remove mold that is currently growing in your home. Controlling your home’s humidity levels and making sure to immediately repair leaks is a good way to control mold growth in your home. Keep in mind that most mold grows in places that are hard to see. If you suspect mold in your home, check out this article for ideas on dealing with this problem.

Can I use an air purifier in the bedroom?

air purifiers are good for the bedroom

Yes! The bedroom is the one room in the home that it is highly recommended that you use an air purifier. It is, after all, the one place in your home where you spend the most time.

Do air purifiers put ozone in the air?

Yes, there are a couple of types of air purifiers that do put ozone into the air. The ozone generating air purifier creates ozone as its name implies. The ozone is emitted into the air to destroy germs and other pollutants. As discussed earlier, it is recommended that you not use one of these devices in your home.

The other type of air purifier that puts ozone into the air is the ionic air purifier and the electrostatic purifier. Both of these units do emit a small amount of ozone as a byproduct of using electricity to create ions and charge plates. However, the amounts emitted vary from unit to unit. Be sure to understand how much ozone the unit you are considering will emit during normal operations.

If you suffer from any type of respiratory ailment, it is recommended to go with the HEPA filtration air purifier to avoid any unwanted issues with ozone.


The subject of using air purifiers to improve indoor air quality may seem to be a complex one but it is really not that complicated. The HEPA filtration air purifier is going to be the way to go for most homeowners in most cases. There are other types of air purifiers on the market and new types coming all the time.

Initial price is not the only thing to consider with contemplating an air purifier purchase. Cost of ownership, or maintenance costs, if you will, are an ongoing expense that must be taken into account.High quality air purifier

With a HEPA unit, you will need to replace filters. This is a cost that a lot of folks don’t think about.

UV air purifiers will also have a lamp that will need to be replaced.

Ionic and electrostatic purifiers may have collector plates that need to be disassembled and cleaned, which takes time.

Whichever air purifier you decide upon, rest assured that better indoor air quality is just around the corner. Considering that our home’s air is likely 2 to 5 times as dirty as the air outside, the money we invest in air purification seems like a bargain.

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