Five things to consider when buying an air purifier

Whether you have a dust allergy, are a smoker or pet owner, or have seen recent studies on how air purifiers can improve cardiovascular health, you have come to the decision to purchase an air purifier. Unfortunately there are so many options and so many prices, and very little standardization between how they are marketed, leading to difficulty in comparing air cleaners. Luckily, there are 5 main qualities of an air purifier to look for when deciding what is right for your needs. 

1) CADR - Clean Air Delivery Rate

Sizing your air purifier appropriately for the room it will be used in helps you avoid spending too much on a unit that is too large for your needs. The CADR rating helps you determine which air filter is right for you. 

The CADR rating for an air purifier indicates the volume of air that can be cleaned by your unit  within a minute. The CADR rating is calculated separately for three different irritants: tobacco, dust, and pollen. The Association of Home Appliance Manufacturers recommends a CADR of roughly 1/12 of your room's volume. So if you have a standard 1000 cubic foot (volume of air, not square footage of the floorplan), you want a CADR of 83 or higher. 

2) HEPA - 99.9% vs 99.97%

A HEPA (high-efficiency particulate air) filter is the core component of all air purifiers. When you are considering buying a purifier, pay close attention to the percentage of particles the filter will remove and the minimum size of particles. While the difference between 99.9% and 99.97% may seem small, it is in fact the difference between the ability to remove many smaller allergen particles. Look for filters marked 'Pure HEPA' or 'True HEPA' that fiter 99.97% of particles down to 0.3 microns in size. 

3) Filters - Permanent and pre-filters

When you consider the cost of your air purifier, don't forget that you will need to replace the filter every year of regular usage. There are two factors to watch for that may increase or decrease this upkeep cost.

Permanent or washable filters

Many devices now come with permanent or washable HEPA filters which do not need to be replaced, or require much less frequent replacement. While this may seem convenient, many of these filters are limited to 99.9% removal rates. You may need to make a tradeoff between filter effectiveness and long term cost when deciding how to buy an air purifier. 


Air filtration units are not just made up of HEPA filters, but may also include pre-filters that handle a range of tasks to provide additional air cleaning power. The first is they are very good at removing the larger particles of dust and hair to keep replacement cycles long for the more expensive HEPA filters. Second, they will often be carbon-based filters which are very effective at eliminating odors, especially that of smoke. If tobacco odor is a main concern, this is a must-have feature. 

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4) Energy Consumption

Once you have bought an air purifier, chances are it will be running 24/7 to keep your home healthy. 

EnergyStar certified

EnergyStar is the gold standard for efficiency in electronics, and an air puifier which has this certification or approval will keep your electricity bill down while keeping your air clean. 

Mulit-Speed and Automatic mode

Chances are you will not always be in the room that is being cleaned, or you may be sleeping in the same room. Check for at least three speeds: Low, High, and Sleep. This will let you adjust to your needs, when you need more cleaning or need silence for sleeping. An Automatic mode can be helpful as well, which detects the level of irritants in the air and sets the power accordingly. By not having your air purifier on full speed all the time, you can save on your energy bill. 

5) Ionization

Another key feature of air purifiers is an ionizer. These work by creating electric charges on the particles in the air as they pass through the filter. This helps the charged particles get caught up by the HEPA filter more efficiently. In addition, the particles which escape the filter will fall to the ground and stick more easily to walls and floors, allowing much easier cleanup by vacuum or dusting. Instead of continuing to float through the air where you breathe them in, they adhere to surfaces due to their charge and are easily handled. 

6) Bonus features

The five features above are necessary considerations when deciding how to buy an air purifier, but there are many extras you may wish to keep in mind.

Remote Control

Easily turn down your air purifier from bed or across the room when getting ready for sleep. 


A panel on the top of the unit may show things like dust levels in the air, or whether it's time to replace a filter. 

Included filters

When you buy an air purifier, it may already come with filters. If not, you may need to spend an extra $50-$100 before you can even use the air cleaner.


Using a remote is too much work? Set your unit to turn down automatically when it's night time. 

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Things to watch out for

When deciding which unit is right for you, make sure to read several air purifier reviews if possible, and even if all of the key features are present there are a few you want to avoid. 

Ozone production

Ozone is a form of oxygen which is produced by the electricity used in the ionizer of an air purifier. This is the same as ozone in the atmosphere which is produced by lightning, and is unfortunately a lung irritant and harmful in large quantities. While you won't be able to buy an air purifier which produces harmful levels of this gas, the unit is meant to clean your air so avoid ones which produce ozone if possible. 


Units made primarily of plastic, especially on the lower end of the price scale, can release harmful gasses into your air as well as undesirable odors. Again, an air purifier which dirties the air is self-defeating. Read reviews for owner complaints of plasticky smells and how long they last after purchase. 


Even with multiple speeds, some air purifiers will just be noisy. This may be due to poor construction causing rattling or squeaking, or over-powered fans. Pick the right size for your room, and consider your noise tolerance within the room it will be placed. Noisy could be fine for a rec room, but in a bedroom you often want whisper quiet fans for sleep.