Air Purifier Buying Guide

A great air purifier can really improve your life, reducing allergens such as pollen and mold spores and protecting against smoke from fires and other types of smoke.

An Air Purifier consists of two important components: Filters and fans. With the help of the fans, the air purifier draws in the polluted room air and passes it through the filters. During this process, particles and harmful bacteria in the polluted air are retained in the filter, and the clean air is released back into the room. The higher the quality of the air filter, the cleaner the air.

The greater the capacity of the fans in the air purifier, the more air it can filter. Some air purifiers do not have physical filters, but rely solely on technologies such as ionization, electronic separation, and UV lamps. With such methods, you may not get as clean air as with air purifiers that have physical filters. Some of them may even have negative health effects on your body.

Size of an Air Purifier

Before you decide on the exact size of an air purifier, you need to calculate the square footage of the room you want to clean. To do this, measure the length and width of the usable space in feet and multiply them. Decide on an air purifier with a recommended square footage that matches your room’s floor space by referring to the technical specifications.

An air purifier will take about 15-20 minutes to clean the air and then recirculate it, depending on the size of the room. For best results, buy an air purifier that is slightly larger than the specified room size. Also, the air purifier is more effective when the doors and windows are closed, because then it does not have to constantly clean the polluted air.

Choosing Type of Air Purifier

Filtration Systems

Air purifiers with filters are the most popular and widespread type. At its core, a fan pulls air through a pleated paper or mesh filter that traps particles inside and purifies the air. The air filter itself can be a permanent and washable model or a replacement filter.

If you have to choose between the two, keep in mind that washable filters will trap dust, but not pollen and smaller particles. Many newer air purifiers are equipped with pre-filters that trap larger particles in the air stream, increasing the efficiency and life of the main filter.

Electrostatic Precipitators

The second most common type of air purifier, electrostatic precipitators draw air through an electric field and use an electric charge to trap and separate particles on charged metal plates or filters.

Some units use a fan to circulate more air at once. These air purifiers release a small amount of ozone into the air, which is an important factor if you are using the unit in a small room.


Both filter systems and electrostatic precipitators can have a built-in ionization circuit. Ionizers discharge electrons into the air and form negative ions that attach to air molecules. The negative ions attract dust and pollen, forming larger particles that are more easily captured by filters. An ionizer helps the air purifier work more efficiently. However, the ionized particles can also attach to upholstery, curtains and carpets, requiring more vacuuming.

Types of Air Filters found in Air Purifiers

There are several types of air filters used in air purifiers. In some cases, several are used in a single unit.

HEPA Filters

HEPA filters are one of the best solutions for allergy sufferers. They retain at least 99.5% of smoke, mold and dust particles in the air. The captured particles can be invisible to the naked eye and have a diameter of only 0.3 microns. The same technology is also used in many high-quality vacuum cleaners.

Ozone Filters

Ozone filters are good for removing odors from the air, but they are not capable of removing chemicals or allergens. The gas produced by ozone filters has been shown to be harmful to humans when used in a room that is not well ventilated. So be sure to follow the manufacturer’s instructions when choosing this type of filter.

Carbon or Charcoal Filters

When air passes through a carbon filter, contaminants such as odors, smoke, and chemicals are removed from the air and trapped in the porous carbon. Charcoal filters are generally not able to remove bacteria or allergens from the air.

Ionic or Ionization Filters

Using a small electric field, ion filters remove small suspended particles from the air by charging them either negatively or positively. The negative or positive particles are then pulled out of the air by plates containing the filter. This type of filter is best suited for removing fine particles from the air, such as smoke and dust.

Ultraviolet Filters

The passing air is immersed in UV light emitted by an ultraviolet filter that neutralizes potentially harmful microbes and bacteria. Ultraviolet filters are generally not a good choice if you are concerned about allergens, chemical fumes, smoke or odors.

Most Common Reasons for Getting an Air Purifier

Air purifiers are quite diverse in form and function, and while they all do essentially the same thing, each is designed to meet a different household need. This begs the question: Who might benefit from an air purifier?

Allergy sufferers

Pollen and dust are two common allergens, especially in the spring months when all the flowers start to bloom. Pollen can enter your home through people coming in and out, or be blown directly into your home through windows and doors. Eliminating these particles will reduce the effects of breathing difficulties, sneezing, runny nose, itchy eyes and irritated skin.


Asthma is a common respiratory problem that affects people in varying degrees. As with hay fever and other allergic reactions, using an air purifier can reduce the amount of irritants in areas where you spend the most time, such as your living room or bedroom. Asthma sufferers have even reported sleeping better when an air purifier is active in their room.

Households with smokers

An air purifier is especially important in homes with a mix of smokers and non-smokers, as it can capture and circulate pollutants to reduce the effects of secondhand smoke. It can also prevent intense smoke odors from lingering in the home.

Pet owners

Life would be much duller without our feathered, furry and scaly friends, but the presence of pets generally means an increase in pet hair and dander. Think of a dog that alternates between being indoors and outdoors, and how those movements would lead to the widespread spread of pollutants.

Pets can also pick up pollen, dust and other irritants in their fur or on their skin and spread them throughout the house. An air purifier ensures that you can spend time with your best friends without worrying about air quality.

Young children

For infants and toddlers, living in an unpolluted environment is incredibly important, as their immune systems are not yet fully developed. With younger children, their constant running around and mischief can introduce potential pollutants into your home. With an air purifier, you can ensure that your children are always breathing high-quality air.

Features to look for

Sensors and Timers

Most air purifiers have sensors that, in addition to other measured values such as room air temperature and humidity, also determine the degree of pollution in the air around them. Usually, this information is displayed on the device or (for models with Wi-Fi connection) in an associated app, for example as a detailed particle count or as a simple color display (e.g. green for good air and red for heavily polluted air). Some devices can be set to activate automatically when air pollution reaches a certain level. This can be convenient if you want the air purifier to maintain good air quality without having to run it 24/7.

If automatic sensors are not available, a simple timer function can be useful to run the unit at certain times of the day. It can be very interesting to see how much dust or smoke is in the air of your home and what kind of activities are contributing to the pollution.

example, frying food on a gas cooktop can quickly release a large amount of pollutants (even if the food doesn’t burn!). Spraying insecticides, using cleaning products, and painting also release chemicals and fine aerosol particles into the air. You may also want to set the air purifier on automatic so it adjusts its speed to the level of pollution – if you hear it revving up, that may be an indication that smoke or other pollutants are entering the home.


Look for an air purifier with a good range of fan speeds. You need a strong airflow when you need to clean the air in a room quickly, but a gentle airflow for use in a bedroom at night. An oscillating fan is useful for cleaning a larger portion of the room.

If the air purifier doesn’t have a good selection of fan speeds (or doesn’t have a fan at all), you should use a regular fan in the same room, such as a floor or ceiling fan. It is important to provide good air circulation while the air purifier is in operation – otherwise it may only clean the air around it, leaving pollutants in other parts of the room.

Wi-Fi Apps and Remote Controls

A remote control is very convenient, but not all models have one. Some air purifiers can be connected to your home’s Wi-Fi network and controlled via a smartphone app, which can be an alternative to a dedicated remote. With some models, such as Dyson’s Pure Cool and Pure Hot + Cool (but not currently with the Pure Cool Me range), you also have access to the air purifier’s collected data, so you can see what kind of pollutants it has removed from your home.


Air purifiers can be quite heavy – they can weigh 10 kg or more. So if you want to transport the device from one room to another, make sure that the weight is portable. Wheels and carrying handles can make transportation easier.

Additional Features to Consider

The magic of the air purifier depends on what type of filter you need and want to use, but there are numerous additional features found on air purifiers to make your life easier.

Filter life indicator

Depending on the type of filter, they need to be changed to ensure that the air is cleaned evenly. To keep you on top of things, a filter life indicator automatically warns you when it’s time to change the filter.

Quiet operation

The whisper-quiet operation of some air purifier models makes them ideal for babies, toddlers and light sleepers.

Automatic air quality monitor

While your air purifier is in operation, special sensors monitor the air and automatically adjust the purification speed accordingly.

Antimicrobial agents

These agents prevent the growth of mold and mildew on the filters.

Light indicator

Some models are equipped with sensor lights that show you at a glance how the air quality is in a room.

Speed Settings

With multiple speed settings, you can adjust how fast you want your air filtered.

Energy Efficiency of Air Purifiers

Air purifiers are most effective when they run almost constantly, so you should also consider the cost of electricity. Some of the air purifiers we recommend are Energy Star certified, but each of them consumes different amounts of electricity depending on the fan speed.

Small air purifiers like the Levoit LV-H132(opens in a new tab) tend to use less energy than larger units, but they also clean much smaller spaces. Conversely, air purifiers that are designed for large rooms and have a higher fan speed, like the Coway Airmega 400, tend to use more energy. Some air purifiers have an “Eco” mode that turns the units off and puts them into standby mode when their sensors no longer detect air pollutants.

What is the Clear Air Delivery Rate?

The Clean Air Delivery Rate (CADR) is an industry standard measure of the volume of air that the air purifier can clean. It is expressed in cubic meters per hour (or cubic feet per second). The larger the number, the better.

The CADR test is performed in a small room (a square room with sides about 3.4 m long and 2.4 m high), with the air purifier in the center of the room and set to the highest speed setting. This is a 20-minute test conducted separately for each of the three pollutants (dust, tobacco smoke and pollen). As a result, some models report their CADR values for each pollutant type.

While the CADR value is useful for comparing the performance of different models, it is not necessarily a good indicator of how an air purifier will perform in your home. You’re more likely to place the air purifier at one end of the room or in a corner, and not always use the highest speed setting.

Dyson has developed its own testing method called POLAR, which can be used to test performance in a more typical environment. This test takes place in a larger room, with the air purifier placed in a corner, and can be used for a variety of pollutant types.


The performance of an air purifier is determined by the CADR (Clean Air Delivery Rate) ratio. The CADR value indicates the maximum area where the filter should be used and how quickly it can remove the three types of pollutants: Smoke (with a number between 10 and 450), Dust (10 to 400) and Pollen (25 to 450). The higher the CADR value, the more effectively the device filters the air. The ideal value is 300 and anything above that is excellent. A value below 100 is very poor and does not clean the air.

If you choose a cheap air purifier with a shorter warranty period, it may not be as effective and you may have to replace the unit soon. It is always better to buy an air purifier from a reputable and trusted manufacturer with a comprehensive warranty. There are many brands that sell these devices, but for accuracy and credibility it is better to choose well-known brands like Philips, Panasonic, Eureka Forbes, Kent, Breathwell and others.

Selecting the Right Accessories

Choosing the best air purifier may also mean choosing the air purifier with the best features and accessories. Air purifiers do not use the same filters and are not equipped with the same accessories. Some air purifiers  come with a remote control or control monitor. They may be equipped with one or more sensors and have applications to connect them to other home automation systems.

Low and mid-range air purifiers often do not have a digital display. Therefore, since they do not provide data on air quality and the presence of indoor pollutants, it is impossible to know whether they are working properly or not.

What is the Total Cost of an Air Purifier?

When considering buying an air purifier, you should take into account not only the purchase price but also to the operating cost which includes:

Price of Filters

The price of filters, as well as how many there are and how often they need to be changed. Changing an air purifier’s filter every quarter is expensive and bad for the environment. Keep an eye out for purifiers that use multiple filters that need to be changed individually and that come at a high price.

Energy Consumption

The energy consumption, which usually will stay reasonable unless the air purifier comes with options such as heating or AC. High-end purifiers are usually single-function and offer a “sleep” or “energy saving” mode to consume less.


By Reading this guide, you can narrow down your choices and make a well-informed purchase. Be sure to balance features and prices when comparing them. Consider different models that offer the features you want and choose the one that fits your budget.

Editorial Staff
Editorial Staff
The Bollyinside editorial staff is made up of tech experts with more than 10 years of experience Led by Sumit Chauhan. We started in 2014 and now Bollyinside is a leading tech resource, offering everything from product reviews and tech guides to marketing tips. Think of us as your go-to tech encyclopedia!


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