Air Purifier vs. Diffuser: A Beginners Guide

  • By: Sue Dorrens
  • Date: February 22, 2022
  • Time to read: 8 min.
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According to most experts, indoor air quality is a lot worse than the air we breathe outdoors, but a good air purifier will trap most pollutants in the air so they don’t get the chance to be inhaled by anyone in the room.

When looking for the right air purifier, it’s a good idea to know the difference between air purifiers and diffusers or you’re likely to be disappointed in the results.

Air Purifier – Purifies air by extraction and filtration.

Diffuser – Pumps nice-smelling air into a room without extraction or filtration.

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Are Air Purifiers and Diffusers the Same Thing?

An air purifier has filters, usually two or more of them, that trap pollutants in the device so that you don’t breathe them into your lungs. This includes dust, pollen, pet dander, bacteria, and other small particles.

On the other hand, diffusers simply make a room smell better. They contain water that you add essential oil or scented oil to, and the scent is misted into the air to keep it smelling good.

Air purifiers often have activated charcoal filters in addition to filters that trap pollutants, and these charcoal filters reduce the bad odors in the air so the room smells better.

As a general rule, you cannot place any type of oils into an air purifier. Good air purifiers will reduce the bad smells in the room, but they do not add pleasant smells. For that, it’s better if you buy a diffuser, add water to it, and then sprinkle a few drops of lavender, eucalyptus, or other scented oil to instantly improve the smell in the room.

Check out our article Xiaomi Air Purifier 3C Versus 3H – Full Product Comparison with Key Differences.

What Is an Air Purifier?

If you have allergies, asthma, or any other type of upper-respiratory problem, a good air purifier will help reduce your symptoms. Air purifiers usually have at least one filter to absorb pollutants and another to get rid of bad odor. The filters that absorb pollutants are usually HEPA filters, which are the best. A “true” HEPA filter removes 99.97% of all harmful pollutants in the air down to 0.3 microns in size, which is roughly the size of 1/200 of a strand of hair.

Air Purifiers

Indeed, nothing gets past a true HEPA filter, and if you’re unsure if the filter used in your air purifier is one of these filters, simply remove it from the unit and take a look at it.

If you want to make sure that you get a true HEPA filter, look for two bits of information on the filter itself:

  • Cleans 99.97% or more of the pollutants in the air
  • Clean particles down to 0.3 microns in size.

If it states those two things on the filter, it is a true HEPA filter because, by law, a true HEPA filter has to fulfill these two requirements. True HEPA filters simply zap much more pollutants than any other type of filter, which is why they are recommended for allergy sufferers.

Of course, you can easily purchase air purifiers with other types of filters, which are usually cheaper than true HEPA filters. If you don’t suffer from allergies or your allergies are not that bad, a less expensive filter will probably be fine. However, people with severe or regular upper-respiratory problems need at least a HEPA filter, preferably a true HEPA filter. And HEPA filters usually last for a while because many of them can be removed and cleaned, so you’re always getting your money’s worth.

If you’re researching air purifiers and the manufacturer claims the filter is “HEPA-like” or something similar, then you’re not getting a true HEPA filter. So, if a true HEPA filter is what you want, make sure that you look for the two numbers listed above so that you can feel confident about the air purifier you purchase. The good news is that a true HEPA filter is easy to find, so if you have any type of breathing problems whatsoever, this is the kind of filter you want.

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Check out our article Air Purifiers with Water – Our Top Five Picks.

What Is a Diffuser?

Unlike an air purifier, a diffuser, or air diffuser, as some people call it, has only one purpose: to spritz a very pleasant smell into the air so that it smells much better. Most diffusers have two compartments. The first is the light source at the bottom, which usually holds a candle, usually a tealight, or some type of built-in light bulb. The second compartment is the top portion of the unit, which is where you place a small amount of water.


Next, you sprinkle several drops of some type of essential oil or scented oil into the water, and when the water is warmed up by the tealight or light bulb, the scent is misted into the air. As long as the unit is turned on, the scent will continue to permeate through the air, but you can enjoy it longer than that because the scents last a while. And if you’re wondering what the difference is between essential oil and scented oil, the answer is quite simple.

Diffusers do the following:

  • Make a room smell nice
  • Improve ambiance
  • Help provide a calm atmosphere

Essential oils are oils made from the leaves, branches, and flowers of different plants. It takes a lot of those plants to make just a tiny bit of oil, and therefore these oils tend to be more expensive. For instance, it takes several tons of rose petals to make just a small bottle of rose oil. But there is good news when it comes to essential oils. If you buy 100% pure essential oils, there will be nothing added to them. Because of that, you only need a few drops of essential oil to enjoy a nice hefty scent.

If you’re shopping for essential oils and it doesn’t say “100% pure” on the bottle, it’s usually blended with other oils, usually a carrier oil. Because it is essentially diluted at this point, you may have to put more than just a handful of drops into the water to get the same scent.

In fact, many “essential oils” will state right on the bottle that it is already blended with a carrier oil or mixed with other oils, which makes them a lot less potent. Nevertheless, these types of essential oils are cheaper than pure essential oils and are just what some people are looking for.

The closer you get to a pure essential oil, the stronger the scent will be and the fewer drops you’ll need to add into the water. But whether you use essential oil or oils made with synthetic scents, you’ll still be able to enjoy a nicer-smelling atmosphere in your home or office.

Is Aromatherapy Real?

If you decide to use real essential oils, also known as aromatherapy, it’s good to know that aromatherapy is proven to be effective. In other words, the results from aromatherapy are real. Lavender really does relax the senses, and eucalyptus really does help unclog sinuses.

If you’re using an air diffuser because you want some type of medicinal results from the essential oils, you won’t be disappointed. If you’re using 100% pure essential oils, you should add three to five drops to your diffuser. Mixed blends will usually require eight to ten drops instead.

There are also different types of diffusers, and while each of them works great, they do work in different ways. For instance, an ultrasonic diffuser releases microparticles as a mist as a result of vibrations caused by electronic frequencies. If you have small or medium-sized spaces, these diffusers will work just right. You can even mount them onto your air ducts if you want to cover more ground.

A nebulizing diffuser provides an intense aroma but is made out of glass so it is rather fragile. Once you set one of these diffusers on a tabletop, they give off a fine mist that evaporates into gas form. Some people prefer diffusers that use heat instead of any type of vibration to heat the oils, like the ones that heat the water and oil via a candle or light bulb. In addition to these types of diffusers, there are also diffusers that have a hot plate at the bottom of the unit and heat up after it is plugged in.

Air Purifier and Diffuser Combo

While aromatherapy is proven to reduce stress and depression and allows people to sleep better, there is a downside to essential oils. After essential oils are evaporated and emitted into the air, volatile organic compounds (VOCs) can be released into the air. This is especially true with lavender, tea tree, and eucalyptus oils, although other oils do the same thing.

Excessive VOCs are not good for the air or for your lungs. The thing is that if you have both a diffuser and an air purifier, the latter may help to get rid of those VOCs, as long as you have an activated charcoal filter along with your HEPA filter.

In other words, while a HEPA filter doesn’t get rid of VOCs, an activated charcoal filter does. And since air purifiers almost always have both of these types of filters, you can use them to get rid of the VOCs in the air and to make the air a lot less smelly. In fact, there are now units that combine an air purifier with a diffuser so that you get the best of both worlds. Depending on your own individual needs, these combo units may or may not be satisfactory to you. You’ll have to decide that for yourself.

Nevertheless, having both a diffuser and an air purifier in your home is never a bad idea. Each of these units serves a specific purpose, but when you keep in mind what specific purpose each of them has, it’s a lot easier to decide which one is right for you. With air purifiers, you often have to regularly clean or purchase other filters, which is something to remember. Diffusers usually only need water, oils, and sometimes candles, so these are generally cheaper to maintain.

Of course, the two units serve completely different functions. An air purifier cleans the air and gets rid of pollutants in the air, both small and large, and traps them inside of the unit so that you don’t breathe them in. Air purifiers are great for allergy sufferers and those with asthma or other upper-respiratory ailments. Without these pollutants in the air, you can breathe a lot easier and better.

Diffusers do nothing to clean the air, but they do release pleasant scents into the air so that the room smells better. But if you decide to add pure essential oils to your diffuser, you can reap some medicinal benefits as well as enjoy a pleasing scent. While diffusers don’t remove anything harmful from the air, they do release a nice aroma into the air, which can make breathing a lot easier. You can also find units that are air purifiers and diffusers in one.

Final Words

Air purifiers and diffusers are not the same thing. In fact, air purifiers clean the air of pollutants and diffusers emit pleasant scents into the air to make the entire room smell great.

Whether you have breathing problems or simply want the room to smell better, you can easily find the device that is perfect for you. Even better, neither of these machines is especially expensive, so you should be able to find a unit that works well and won’t break the bank.

You might also like Best Air Purifiers for Basements – Top Five Picks.

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