How To Choose The Best Air Purifier

Since it’s a matter of health, you should be extra careful while buying an air purifier for your home. If you are not aware of the functionalities of each type of filter or other factors, it might be difficult for you to buy one model out of so many options. To help you with this, here is a detailed buying guide that will help you buy the best air purifier for your home.

air purifier buying guide

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1. Air Purifier Filter Types:

Different filters of air purifiers target different types of air pollution. The pollutant that they target depends on the filtration technology that is used in the unit. We have explained about each filter below.

Most of the air purifiers these days come with prefilters. A Prefilter is generally the first layer of the filter that is fitted in front of the main filter. It is responsible for removing large particles of dust from the air. Prefilters are just like any basic filters that remove dust, pet hair or danders, and larger microbes. These prefilters are usually made using foam or nylon and can be washed easily. Hence, it is good to look for an air purifier with a prefilter.

  • HEPA Filter:

HEPA or High-Efficiency Particulate Air Filters are designed to catch 99.97% of airborne particles from the air that measure around 0.3 micrometers or large when they pass through the filter.

HEPA filters can remove dust, hair, smoke, pollen, pet dander, mold spores, and bacteria from the air effectively. If you are suffering from asthma, allergies, or any other respiratory issues and if you are more susceptible to illness, buying an air purifier with HEPA filters can be helpful.

There are many types of filters that use the HEPA acronym but there is only one label that has an actual certification. You should look for the “True HEPA Filter” label. A True HEPA Filter is certified to eliminate around 99.97% of all the microscopic particles that are 0.3 microns small.

A few other filters use terms like “HEPA-type” or “HEPA-like”. These are inferior products that can capture particles that are 2-5 microns small. This leads to a more than 600% decrease in the efficiency of the purifier.

While checking for a HEPA air purifier, make sure you always look for the True HEPA label.

Efficient in trapping small particles up to 0.3 micron Needs regular maintenance
Doesn’t release back the trapped impurities Cannot remove odor, gases and fumes
Suitable for people with respiratory issues Expensive than others
Longer life of the filter Has a fan to suck in air, which is noisy
  • Activated Carbon Filter:

The activated carbon filters help in reducing the odor from the room by absorbing gas fumes, smoke, pet odors, cooking smells, paints, cleaning supplies, and other irritants. If you are sensitive to certain chemicals, you can look for a purifier with an activated carbon filter.

This filter uses a special form of activated carbon that contains millions of tiny absorbent pores. These pores create a larger surface area that makes it suitable for trapping gases, odors, and fumes.

In most of the air purifiers, these filters are used in combination with other filters as the activated carbon filters cannot remove dust particles from the air.

Can remove volatile compounds like gases, odors, fumes, smells, smoke and others Can’t remove small particles
Cheap to replace  
best suited for asthma patients  
Effective for people in industrial areas
  • UV Lamp:

If you are looking forward to buying an air purifier that can kill germs, bacteria, and other harmful particles from the air, you should buy a model with a UV lamp. According to the studies conducted by the California Air Resource Board, a 20 Watt bulb is capable of killing microbes, germs, and pathogens within a few seconds. Since it does not release any ozone byproduct, it is completely safe to use and can even be used in the kitchen, hospitals, and labs.

An air purifier with a UV lamp is perfect for those areas where the climatic conditions are generally moist and humid. As they cannot deal with other types of pollutants, a UV lamp filter is used in combination with other types of filters to provide maximum efficiency. If they are not used with other filters, the microbes can easily hide with the pollutants and get back to the surrounding air. In most of the air purifiers, UV lamp filters are either used with HEPA filters or activated carbon filters.

Capable of lasting thousands of hours It cannot be bough standalone device as it cannot remove pollutants like dust, pollen and others
Rarely needs a replacement Comes with in combination with air purifier filter
Provides sterile environment
  • Ionic Air Purifiers or Ion Generators:

An ionic air purifier is also called as an ionizer, ozone generator, or ion generator. These types of air purifiers emit electrically charged molecules called ions to the air. The charged ions attach themselves to dust, pollen, mold, and other allergens that are present in the air.

This charges the particles so that they attach to each other, making them large and heavy so that they settle down faster. Due to this, the particles cling to surfaces like walls, floors, and furniture. There are a few particles that drift around in the air. They can be inhaled.

While looking at how these ionic purifiers work, you must understand that the air ionizer purifier does not actually capture or eliminates dust particles from your home. The dust particles that have been charged by ions continue growing and spreading and they eventually cling to the surface. These particles can be again stirred up due to activities like dusting, using a vacuum cleaner, or other household activities.

Maintenance free, doesn’t require costly replacements Pollutants remain in the room clinging to the surfaces. You have to use an electro-static plate to remove them
Less expensive than HEPA filters Has to be cleaned frequently
Noise free as it doesn’t use a fan Not capable of removing odors
  Produces a small amount of ozone as by-product which can be an irritant for asthma
  • Ozone Generators:

The ozone filters release ozone while purifying the air. This purification technology is not considered very safe though. If exposed on a daily basis, it can scar the lungs and is not safe for people dealing with respiratory issues. These purifiers are generally used during emergency situations like post floods.


Try to avoid buying an air purifier with ozone generators as it can be hazardous to infants, babies, and elders.

Important Note:

It is always better to avoid buying air purifiers with ozone purification technology.

2. Room Size:

Room size is one of the most important factors that you should check for before buying an air purifier. Smaller rooms require smaller air purifiers and vice versa.

You can find air purifiers in multiple sizes ranging from compact to heavy. Thus, check the coverage area parameter provided by the air purifier and then compare it with the size of your room. It is always wise to buy a model that offers a coverage area that is slightly larger than the size of your room.

To calculate the coverage area, measure the length and width of the room where you are going to use the air purifier. After multiplying both of them, you will get the required rating.

For example – 15’ (length) X 20’ (width) = 300 sq. ft. (required capacity)

If you want to use the air purifiers for multiple rooms like the living room, kitchen, and bedroom, you must combine the areas of all these rooms to figure out the appropriate capacity.

For example – Living room (15’ X 20’) – 300 sq. ft. and bedroom (15’ X 15’) = 225 sq. ft. So, the total capacity that you should look for will be 300 + 225 = 525 sq. ft.

3. CADR(Clean Air Delivery Rate):

CADR i.e. Clean Air Delivery Rate is either measured as a cubic meter of air delivered in an hour or cubic foot of air delivered in a minute.

The CADR rating was developed by the Association of Home Appliance Manufacturers (AHAM) in order to help the customers figure out that how well the air purifier is working and purifying the air within a particular size room.

CADR rating becomes especially important when you are comparing two models of air purifiers so that you can buy the best one.

Not all models of air purifiers list the CADR rating on the specifications list. Only those manufacturers, who have enrolled themselves for the AHAM test independently and received the certification, offer a CADR rating.

The CADR rating measures mainly three types of air pollution:

  • Dust
  • Tobacco smoke
  • Pollen

The measurement of each category ranges between 10 – 450. You can find it on the display as a set of three numbers separated by a slash (/). For example, if the CADR rating of a purifier is 210/200/190, it means 210 is for the dust, 200 is for tobacco smoke, and 180 is for pollen. The higher these numbers are, the better purification the purifier offers against these contaminants.

The effectiveness of CADR ratings is classified as follows:

  • CADR rating Above 240 – Excellent
  • 240 – 180 – Very good
  • 179 – 120 – Good
  • 119 – 60 – Fair
  • Below 60 – Poor

However, in most of the air purifiers available in India, you will generally find only one CADR figure that notifies the smoke CADR rating in cubic meter per hour.

4. ACH (Air Changes per Hour):                 

ACH refers to the “Air Changes per Hour”. The ACH rating of an air purifier indicates how many times per hour can the device exchange air within a room. For ex, if the ACH rating of a purifier is 5x, it means that the full air volume is exchanged 5 times every hour.

ACH is one of the least understood ratings on an air purifier.

Whenever you are comparing two models of air cleansers, checking for the ACH rating is very important as it shows you quickly which product is best to exchange fresh air inside the room.

If one model offers a 4x rating whereas the other offers a 5x rating, the product with a 5x rating is better than the other one.

The more number of times a device can exchange air within the room, the cleaner and fresher the environment inside the room will be.

We suggest you to not buy an air purifier that offers an ACH rating below 4x as it might lack efficiency.

Most of the manufacturers don’t mention the ACH rating on the specification list. However, you can calculate it by yourself and figure out if the air purifier is good or not.

ACH Calculation:

ACH rating = Air changed in an hour / Volume of the room (area X height)

To calculate the ACH rating, you must know the CADR rating of the purifier along with the coverage area (in sq. ft.) that the purifier offers.

Let’s calculate the ACH rating for an air purifier with CADR of 350 m³/hour. Let’s say that we are using it in a room of 300 sq. ft. where the height of the room is around 9 ft.

In India, the CADR on the air purifiers is generally mentioned in m³/hr. You will have to convert this into cubic feet per minute (CFM) by multiplying it with 0.588 (as 1 m³/hour = 0.588 ft³/min).

Thus, CADR in cubic feet per minute – 350 X 0.588 = 205.8 CFM

Now, let’s calculate how much cubic feet of air does the air purifier delivers in an hour by multiplying the CADR (in CFM) by 60.

Air changed in an hour = 205.8 X 60 = 12,348 (CADR in CFM X no. of minutes in an hour)

Room Volume = 2,700 (300 X 9)

Thus, ACH rating = air changed in an hour / Room’s volume

ACH rating = 12,348 / 2,700 = 4.57

5. Placement Considerations:

Installing or placing the air purifier at the correct place also helps in improving the efficiency of the air purifier. Whenever you are placing the air purifier, make sure that there are around 18 inches of space so that there is nothing in between that can interfere with the airflow. Most models of air purifiers take air from the sides. Thus, placing them against a wall or an object might reduce the performance.

Air Purifiers with HEPA or Carbon Filters: These models of purifiers use fans to suck in and out the air. Thus, you must place them at least 2-3 feet away from the wall or the furniture. You should never place these purifiers under the bed or behind the couch as it will restrict the airflow, and thereby, hider the performance.

Air Purifiers with Ionic Filtration: Such models of air purifiers are not dependent on fans for the movement of air. These purifiers emit the ions around 360 degrees angle. Hence, never place these air purifiers near the wall or furniture as it can affect the performance of the device. The best place to keep it is in the center of the bedroom.

6. Noise Levels:

If you want to use the air purifier in your bedroom at night time, you must check the noise emission level of the device. The air purifiers that use UV technique or Ionization techniques don’t generally come with a fan. Thus, the operation here is quite silent.

However, purifiers with HEPA or Carbon filters need fans to exchange the air and operate properly. Such models also allow you to adjust the speed of the fan. Hence, make sure that the air purifier has a minimum fan speed setting so that the noise levels are low.

Most of the purifiers come with 2 level speeds – low and high. Some high-end models of purifiers even come with 5-speed levels including low, medium, high, turbo, and automatic speeds.

We suggest you to buy an air purifier depending on the size of your room. If the size of the room is small, the purifier might have to work hard, resulting in generating more noise.

7. Energy Consumption:

All the air purifiers need a continuous supply of electricity while it is on. So, you might also have to consider the amount that you intend to spend on the electricity bill. Here is how you can calculate the power consumption of the air purifier:

Let’s assume that the air purifier that you bought consumes 50 watts per day. If you are running the purifier for 10 hours a day, the energy consumed will be

50 Watts X 10 hours = 500

Electricity bills are generally calculated in kilowatt-hours which means that the energy consumed while running the appliance at 1 kilo watt per hour.

Let’s divide it by 1,000 i.e. 500/1,000 = 0.5 (kilowatts)

Multiply this with the electricity rate per unit. The average init rate in India us Rs. 5.

So, 0.5 units X Rs. 5 = Rs. 2.5 per day.

This means that if you use 50 Watts air purifier for 10 hours daily for a month, you will get an electricity bill of Rs. 75 per month.

Along with this, also check the energy star rating before buying the purifier as it also determines the power consumption.

8. Filter Replacements:

Along with the total cost of the purifier, you must also check the maintenance cost or the replacement cost of the filters.

Carbon and HEPA filters need to be replaced regularly as they won’t filter air if it is clogged up completely. Thus, if you are going to buy the purifier with these filters, you must check for the instructions provided by the manufacturer to see how often these filters need replacement. Depending on the usage, the filters last for around 3 months to 1 year.

If you are going to buy an ionic air purifier, you might not have to worry about the maintenance costs as they don’t use a degradable filter. Some ionizers come with an electrostatic collection filter that collects all the harmful particles from the air. However, these filters are washable and can be used again.

When compared, ionic purifiers cost less in terms of both total cost and maintenance cost.

9. Additional Features

Some high-end models of air purifiers come with additional features that make it easy to use and operate the device. One thing that you should remember is, with additional features, the price of the air purifier goes up as well.

  • Digital Controls:

With the help of digital controls, you can adjust or control the settings as per your requirements.

  • Filter Replacement Indicators:

This indicator notifies you whenever there is a need to replace the filters. When the filter is filled up with pollutants and can no longer clean the air, you get a notification. In this case, you will either have to replace or wash the filter.

  • Programmable Timer:

The programmable timer feature is available in most of the modern air purifiers. You can set a timer on the purifier on how many hours do you want the unit to work. Once it reaches that time, the machine turns off automatically. This feature is helpful in saving electricity.

  • Carrying Handle:

Carrying or moving an air purifier from one room to the other is not that easy. With the help of carrying handles, it becomes easier for you to move the purifier from one room to the other.

  • Caster:

The functionality of the casters is very similar to that of the handles. You get a set of wheels at the bottom that makes it easier to move the purifier from one room to the other.

  • Anti-microbial Treatment:

The anti-microbial coating prevents the build-up and spreading of bacteria and other microorganisms on the internal filters. This coating also helps in increasing the lifespan of the filter and prevents the re-introduction of the germs back to the air.

  • Air Quality Sensors:

These sensors monitor the quality of air for specific pollutants and then adjust the level of the purifier automatically to remove these particles quickly.

  • PlasmaWave Technology:

PlasmaWave technology works in a very similar way as ionizers. Rather than emitting ozone or negative ions, thus technology uses water vapor to achieve the same results.

  • Photocatalytic Oxidation (PCO):

It is an advanced filtering process that operates in combination with the UV light to oxidize chemicals and destroy all the volatile organic compounds, mold, fungi, and bacteria.

  • Night Light:

Nightlight helps in identifying the place of purifier in a dark room so that you don’t hit it accidentally.

  • Remote Control:

A remote control allows you to operate the purifier or adjust the settings even from a distance.

  • Mobile App:

With the help of a mobile app, you can even control the purifier using your smartphone. It is also helpful in monitoring the quality of air in your home.

10. Brand:

Whenever you are buying an air purifier for your home, we suggest you to buy it from a well-known and reputed brand.

There are so many brands out there claiming to offer the best air purifiers but not all of them are trustworthy. The reason behind this is not all countries have the same rules and regulations on the product as offered in the US and Europe.

Buying an air purifier from a reputed brand helps you get a trustworthy product along with the best after-sale service.

11. Price:

The price of an air purifier ranges between Rs. 4,000 – Rs. 45,000. The price depends on the type of filters used along with the additional features that the product offers. You can buy a model that suits all your requirements.

12. Warranty:

It is very important to consider the warranty period offered by the brand while buying an air purifier. While some brands offer a warranty of 1 year, others offer a warranty of around 5 years. Check all the services that are covered in the warranty period.

How Does an Air Purifier Work?

An air purifier consists of two main components – fan and filter. While some purifiers come with a single filter, others come with multiple filters. The fan helps in sucking in the polluted air and expelling out the fresh air. When you turn the device on, the fan sucks in the air and lets it pass through the filter. After reaching the filter, all the impurities and pollutants are removed from the air. The clean air is then sent out in the surroundings.

The filters present in the air purifiers are either made up using fiber, mesh, or paper. Irrespective of the type of filter used, it needs to be cleaned regularly otherwise it will impact the performance and efficiency of the purifier.

To maintain efficiency, you will have to replace the filters regularly. Thus, in addition to the total cost of the air purifier, you must also add the operational and filter replacement cost.

Benefits of Air Purifiers:

Buying a good quality air purifier can offer a number of health benefits. Some of them are:

  • It maintains clean and healthy air inside the house. According to the EPA, indoor air is two to five times dirtier than the outdoor air. Thus, a good air purifier helps in maintaining a healthy lifestyle at home.
  • It removes the unpleasant odor of burnt food. While cooking foods like fish curry, the house might start stinking.
  • Air purifiers trap airborne allergens, dander, and fur that are generally released by pets.
  • As smoke stinks a lot, the air purifiers can trap and neutralize smoke.
  • The air purifiers even trap dust and reduce its build-up over the surface of your house.
  • Air purifiers can remove up to 99% of airborne bacteria and particles like pollen, mold spores, and bacteria that can make you ill.
  • Seasonal allergies can be a pain for many people and air purifiers can help you combat that too. These allergens can sometimes even make you feel uncomfortable while breathing.
  • The purifiers prevent germs and other diseases from spreading. The air purifiers with True HEPA filters and UV bulbs capture and neutralize up to 99.7% of the airborne germs and viruses.
  • Air purifiers help in maintaining healthy lungs. Constant exposure to dust, pollen, and other airborne particles can cause long-term health and breathing issues.
  • You can place an air purifier anywhere in the house. They come in a variety of sizes with multiple features to circulate healthy and fresh air inside your house.

Other Ways to Improve Air Quality in Home

One of the best ways to address indoor air pollution is to find the source and properly ventilate the rooms. If you want to check if you can deal with indoor air pollution without air purifiers, then we recommend trying the below steps.

  • Keeping the windows open helps to prevent the irritants from getting trapped within the room. If possible, open windows on opposite sides of the room.
  • Vacuum your house regularly. It is better to choose a vacuum that has sealed bag and is HEPA certified because they are best in trapping the dust and don’t recirculate them into the air.
  • Always make sure to change the air filters regularly if you want to maintain the HVAC equipment and maximize the effectiveness.
  • It is better to install exhaust fan in the kitchen, bath and laundry areas. Switch it on before using the rooms. If it is the kitchen, the switch the exhaust fan on before preheating the oven or firing up the stoves.
  • Minimize the usage of candles, lighting wood fires, ban smoking, smoking inside the room. Reducing pollutants sources is sure shot to improve quality

Frequently Asked Questions?

1. Does air purifier cool air in the room?

As air purifiers don’t come with any air cooling mechanism they don’t cool the air present in the room.

2. Is it ok to leave air purifier running all the time?

Yes, you can leave air purifier on all-night or all-day for clean air in the room. However, you have to change the filters frequently. When air filters become dirty, then air purifier will not work effectively. If you want the air purifier to run all the time, then it is very important to check and clean the filters regularly.

3. Which is the best place in a room to keep air purifier?

You have to place the air purifier in the room where air can circulate freely both in and out. And there should be ample free space around the unit, away from furniture, walls and other objects that can interact with air flow. Below are some of the recommendation of placing an air purifier…
*Avoid placing in corners as the walls will interrupt the air flow.
*You have to place it at least 10 cm/4 inches far from obstacles like wall, furniture or others.
*It is better to place the air purifier close to pollution source.

4. Is air purifier good for COPD?

Yes, air purifiers can be helpful for people dealing with COPD as it simplifies breathe by removing airborne pollutants that lead to lung irritation. However, the air purifier has to be equipped with HEPA filter. And avoid air purifier with an ionizer as the ions can trigger COPD symptoms.

5. Does dirty air purifier make you sick?

Yes, it can. You have to clean or replace the filter regularly. Because dying bacteria will feed on clogged and trapped pollutants in filter which can be blown back into the room. Mold spores that have been trapped inside the filter can still stay alive and get also circulate back into the air. This can be make you sick and unwell. So, it is important to clean the air purifier regularly.

6. How long does it take for an air purifier to clean the room?

On an average, air purifier takes 30 minutes to 2 hours to clean air of an entire room. The duration usually depends on fan speed, purifying cover and room size.

7. Does air purifier make air dry?

Nope, it doesn’t. Air purifier is only capable of trapping pollutants like mold, bacteria, dust, mites, pet hair and pollen. It doesn’t have the capability to reduce or increase moisture in the air.

8. Do air purifier decrease immunity?

No, they don’t. Because air quality around your surroundings don’t affect the immunity. Breathing polluted air has been linked into physical and mental ailments like Alzheimer’s and depression. And air purifier can decrease this risk.

9. Is Air Purifier Really Necessary

This is the first thing to do while purchasing an air purifier. If you have been experiencing any of the below issues, then it’s time purchase an air purifier.
*Symptoms of seasonal or pet related allergies.
*No idea what is triggering your asthma attacks.
*Renovating work in or around your house surrounding.
*Feel nauseated because of dust and paint fumes.
*Frequently getting cold and cough.
*If your room needs disinfection to deal with bacteria.
*Have pets that shed dander or if they are reason for odd smells.
*If you or any family member has smoking habit
*If you fall under any of these issues, then purchasing an air purifier is inevitable.

10. Which are the best brands of air purifiers in India?

As brand plays a major role in deciding the quality and effectiveness of the air purifier, it is very important to buy it from a reputed brand. Some of the brands offering the best air purifiers are as follows:
*Blue Star
*Eureka Forbes
*Kent RO

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