Ultimate Guide to Choosing an Air Purifier
by Karl von Luckwald / January 25, 2024
Hey there! Are you thinking about getting an air purifier but some things aren’t clear yet?
Don’t worry, you’ve just come to the right place.
I’ll help you determine what to look for when choosing air purifiers. And I’ll leave no question unanswered. Promised.
Let’s dive in!
How to Choose an Air Purifier
When choosing an air purifier, consider factors like the type and efficiency of filters (HEPA and activated carbon), Clean Air Delivery Rate (CADR) for your room size, energy consumption, noise levels, and additional features. Regular maintenance, including filter replacement, is vital.
Introduction to Air Purifiers
Air purifiers, increasingly popular globally, are essential for maintaining clean indoor air, especially in areas with high pollution or wildfire smoke.
They are crucial for people with asthma, allergies, or those exposed to PM2.5, and chemicals, offering protection from fine dust, allergens, cigarette smoke, and chemical pollutants.
Using air purifiers contributes to better respiratory health and overall well-being by filtering harmful particles and improving air quality.
Air purifiers have become increasingly popular over the past years.
In Asian countries where air pollution is worst, air purifiers are standard equipment in every household.
Since the COVID pandemic and increasing wildfires, air purifiers are also becoming more common in Western countries.
People are experiencing first-hand that clean air can no longer be taken for granted.
Importance of Air Quality
We take 22,000 breaths a day.
If the air we breathe is dirty, tiny dust particles, chemical compounds, viruses, or bacteria enter our bodies.
There, they can cause great damage. Fine dust can deeply penetrate our lungs, bloodstream, and brain – leading to strokes and heart attacks.
Did you know that around 7 million people die from long-term exposure to air pollution each year? This includes not just those in well-known affected regions like India or China.
About 4% of deaths in the U.S. are caused by air pollution, leading to around 110,000 premature deaths annually.
This is more than the number of people who die in car accidents and from shootings combined.
So, clean air is very important for our health.
Air purifiers are helpful because they clean the air, making it safer and easier to breathe.
Who Needs an Air Purifier?
Intuitively, we’d assume that closed doors and windows protect us from outdoor air pollution. Unfortunately, this is not the case. Air pollution will always find its way into our homes.
This means, that indoor air quality is often as bad as outdoor air quality.
So, if you live in an area with a lot of pollution or wildfire smoke, it’s a good idea to get an air purifier for your home.
Air purifiers are really helpful for people with asthma and for those who live with smokers.
If you have allergies to pet hair, using an air cleaner can ease your symptoms.
If you often work with paints and chemicals, think about getting an air purifier.
If you are concerned about viruses and bacteria, get an air purifier too. HEPA filters will catch those little troublemakers
Children, pregnant women, and older adults are especially at risk from air pollution. Air purifiers can offer them strong protection.
Main Reasons to Own an Air Purifier
Understanding the Basics of Air Purifiers
Next, let’s explore what air purifiers do and how they help to keep your indoor air quality at healthy levels.
Air purifiers improve indoor air quality by filtering out pollutants from the air, using a combination of fans and filters, primarily HEPA filters. These devices are effective against a wide range of pollutants, including dust, pollen, viruses, and even nanoparticles.
HEPA air purifiers are highlighted as the most proven and cost-effective option for maintaining healthy indoor air.
What Does an Air Purifier Do?
Simply put, an air purifier cleans the air. It sucks in polluted air from your room, filters out all the nasty particles we want to get rid of, and then sends clean air back into the room.
It’s an ongoing procedure, and within 30-60 minutes, your air should be purified.
How Do Air Purifiers Work?
Air purifiers are simple machines and work on an easy principle.
They consist of little more than a fan and HEPA filter. The fan pulls in dirty air and pushes it through the HEPA.
To visualize it, think of a HEPA filter as a fine-meshed net, capturing everything from large leaves (dust and pollen) to tiny, invisible minnows (viruses).
It’s this versatility that makes them incredibly effective against all kinds of pollutants – even nanoparticles that are on average 8,750 times smaller than human air.
Other types of air purifiers (we will get back to them later) use electrostatic attraction, ozone, or UV lights to improve indoor air quality.
What we already can say, however, is that HEPA air purifiers are the most proven and cost-effective devices available.
Indoor Air Pollutants: What You’re Up Against
Great, you’ve just learned how air purifiers work.
Now let me provide you with some more information on various indoor pollutants air cleaners protect you from.
Indoor air pollutants, including PM2.5 particles, allergens, viruses, bacteria, mold, and TVOCs, pose significant health risks, ranging from respiratory issues to heart attacks.
Air purifiers with HEPA filters effectively trap these harmful particles, while activated carbon filters absorb chemical pollutants. These devices play a crucial role in reducing indoor air pollution and promoting a healthier living environment.
PM2.5 (Fine Dust)
Air pollution consists of tiny particles smaller than 2.5 microns in diameter. That’s why we call them PM2.5 (Particulate Matter).
These guys are the most concerning as they are small enough to enter our bodies.
Once in our bloodstream, PM2.5 can clog our veins which increases the risk of heart attacks and strokes.
Scientists in Mexico even found PM2.5 pollutants in human hearts. Yikes!
PM2.5 comes from various sources. These include wildfire smoke, factory and car emissions, tire abrasion, and construction sites.
PM2.5 particles are around 35 times smaller than a human hair.
Allergens like pollen, pet dander, and dust mites are tiny particles that cause allergies.
They can lead to symptoms like sneezing, itchy skin, and coughing.
Air purifiers with HEPA filters are effective in trapping these allergens, providing relief for those with allergies.
Viruses are tiny infectious agents causing illnesses like colds and flu.
They’re much smaller than bacteria and can spread easily, especially in enclosed spaces.
HEPA filters in air purifiers can capture these tiny particles, reducing the risk of spreading infections, particularly useful in households with sick individuals.
Bacteria are microscopic organisms that can cause various infections.
Some bacteria are harmless, but others can lead to serious health issues. Air purifiers with HEPA filters help reduce the presence of bacteria in the air, promoting a healthier indoor environment.
Mold is a type of fungus that thrives in damp, humid conditions.
It releases spores into the air, which can cause allergic reactions and respiratory problems.
Air purifiers with HEPA filters trap mold spores, preventing them from spreading and helping to maintain healthy indoor air quality.
TVOCs (Total Volatile Organic Compounds)
TVOCs are chemicals found in many household products like paints, cleaning supplies, and air fresheners.
They can evaporate into the air and cause health issues like headaches, nausea, and long-term health effects.
Air purifiers with activated carbon filters are effective at absorbing these chemical pollutants, reducing their concentration in indoor air.
Each of these pollutants poses a unique challenge, but air purifiers equipped with HEPA filters can significantly reduce their presence, contributing to a healthier indoor environment.
Choosing the Right Air Purifier for Your Needs
Congratulations, you’re almost halfway through becoming an air purifier expert.
The following part is about finding the best air purifier for your personal needs.
Hundreds of brands and models are competing for your attention. But let me tell you: finding the right air purifier is not that difficult – if you pay attention to the right metrics.
When choosing an air purifier, it’s crucial to consider the Clean Air Delivery Rate (CADR) to ensure it’s suitable for your room size, with recommended CADR ratings provided for different room sizes.
Other important factors include energy consumption, typically 35-50 watts per hour, and noise levels, ideally below 50 decibels for quieter operation. Calculating Air Changes per Hour (ACH) using the CADR helps determine the efficiency of the air purifier in cycling air in the room.
Find an Air Purifier That Fits Your Space
It’s important you end up with an air cleaner that is strong enough to cover your room size.
If your air purifier turns out to be too weak, it won’t provide you with enough fresh air. Ultimately, your space remains polluted.
To find out whether an air purifier can keep up with your room, go and look out for a metric called CADR.
CADR is every air purifier’s most important number.
The Importance of Clean Air Delivery Rate (CADR)
CADR (Clean Air Delivery Rate) tells you what volume of air your air cleaner can purify per hour. The higher the number, the stronger the air purifier.
CADR is either stated in cfm/hr (cubic feet per hour) or m³/hr (cubic meters per hour).
You’ll need CADR to do some important math.
Calculating Air Changes per Hour (ACH)
For fresh air, your air purifier should cycle the air in the room a certain number of times each hour.
According to our experience, 3-4 air changes per hour are enough to clear out airborne particles. If you are particularly concerned about filtering viruses, the WHO recommends 6-12 air changes per hour. (p. 5)
To calculate this number, use the CADR.
If it’s given in cubic meters per hour (m³/hr), simply divide it by the total volume (m³) of your room.
If the CADR is stated in cubic feet per minute (cfm), multiply it by 60 and then divide it by the room volume in cubic meters (m³).
Either way will lead to the total number of air changes per hour.
For instance, if your air purifier’s CADR is 350 m³/hr and your room volume is 100 m³, the air changes per hour would be 3.5 (350 ÷ 100).
Below, we’ve compiled a list of recommended Clean Air Delivery Rates (CADR) for different room sizes.
|Room Size (m2)
|Recommended CADR (m3/hr)
Other Performance Metrics
CADR is the most important metric for choosing the right air purifier for your needs.
However, it’s also a good idea to look at how much energy it uses and how noisy it is.
Air purifiers use electricity, so it’s good to check how energy-efficient they are before buying to avoid unexpected high power bills.
Air purifiers are mainly fans and filters, so they don’t use a lot of energy. Most use about 35 to 50 watts (W) per hour when on high.
For example, if your air purifier uses 40 W and you run it for 8 hours daily, and if electricity costs 14 cents per kWh, your yearly electricity cost for the purifier would be about $16.35.
Air purifiers don’t use much energy. Based on our calculations, using an air purifier for 8 hours a day will cost about $15 to $20 per year.
It’s also important to consider how loud an air purifier is.
Many brands advertise their air purifiers as being “whisper-quiet”, but this is usually only true at the lowest fan speed. At high speeds, they can be as loud as vacuum cleaners.
On days with a lot of pollution, you might need to run your air purifier at its highest setting. If you don’t like noise, here’s what you can do:
Types and Features of Air Purifiers
Air purifiers come in different types and with different features. We’ll guide you through them, highlighting what’s essential and what’s optional.
Air purifiers come in various types, with HEPA filters being the most popular and cost-effective for trapping pollutants like pollen and viruses.
Activated carbon filters are used for absorbing volatile organic compounds, and many purifiers combine both HEPA and activated carbon filters for comprehensive protection.
Ionizers and UV lights are additional features, but their effectiveness is debatable, with ionizers moving particles around rather than trapping them and UV lights being too weak to significantly impact virus elimination.
Overview of Different Types of Air Purifiers
Over the past decade, more and more air-purifying technologies emerged. We’ll start with the most popular one: Air purifiers that contain a HEPA filter
Air Purifiers With HEPA Filters
HEPA (High-Efficiency Particulate Air) filters were invented more than 80 years ago, and no company on this planet has a patent on them.
These filters are affordable to produce and great at trapping various pollutants. They’re made of randomly woven fibers that are arranged in a way that lets air flow through but are still dense enough to catch different pollutants, from pollen to viruses and tiny particles.
Air purifiers with HEPA filters are the most widely available and cost-effective solution.
Air Purifiers With Activated Carbon Filters
While HEPA filters protect you from solid particles, activated carbon filters absorb volatile organic compounds (VOCs) from the air.
An activated carbon filter consists of porous charcoal granules that soak up chemicals from the air.
For complete air pollution protection, using both a HEPA and activated carbon filter is ideal. Many air purifiers include both types of filters by default.
Air Purifiers With Ionizers
In the last ten years, many air purifier makers have started adding ionizers.
Ionizers send out negative ions into the air. These ions stick to positively charged particles, like dust.
Then, the particles fall onto surfaces like desks, floors, or clothes. So, ionizers don’t remove particles, they just move them around.
Ionizers can improve an air purifier’s Clean Air Delivery Rate (CADR). However, since they don’t trap particles like HEPA filters do, their overall effectiveness is debatable.
There are two more downsides to ionizers.
Firstly, they make things dirty. Look at the Blue Air air purifier below. It’s full of sticky dust particles.
Secondly, some ionizers produce ozone, which is a lung irritant and pollutant we want to avoid.
Would I recommend ionizers? Not really. Air purifiers with HEPA filters are already very good at filtering out particles.
Air Purifiers With UV-Lights
HEPA filters are great at catching viruses, but they don’t kill them. UV lights can kill viruses, which is why quick-witted air purifier manufacturer added them to their air purifiers during the Covid-19 pandemic.
However, UV light in air purifiers isn’t as effective as you might think. They turn out to be too weak to make a big difference.
This is the reason why air purifiers with UV lights were strictly excluded from most public tenders during the pandemic.
Features and Extras
We’ve just covered different kinds of air purifiers. Now let’s have a look at the most popular features of air purifiers.
Air purifiers offer various features like built-in air quality sensors, filter service indicators, and auto settings, but their accuracy and effectiveness can vary.
Manual operation with external air quality monitoring is often more reliable than relying on built-in sensors. Additional features like fan settings, remote controls, Wi-Fi capabilities, and portability options (like handles and wheels) cater to convenience and user preference.
Built-in Air Quality Sensors
Have you ever seen a PM2.5 particle, a virus, or an allergen with your own eyes? Probably not. So, how can you be sure an air purifier is actually working?
To make the invisible visible, most air purifiers come with an air quality sensor that shows the level of fine dust in your room.
These give you a rough idea about the air quality, but they’re usually not very precise. They use infrared beams to guess the amount of fine dust, which isn’t the most accurate method.
Also, these sensors only measure air quality near the air purifier, where it’s usually the best.
To test if your air purifier is effective, you should use a separate air quality monitor with laser diffraction, placed on the other side of the room. If the air quality is good there, then you know your air purifier is doing its job well.
If you’re looking for precise and elegant air quality monitors, I recommend the Qingping devices below.
Filter Service Indicator Light
Some air purifiers remind you when to replace the HEPA filter. They do this by counting the hours the purifier has been used.
But there’s a catch: the reminder system doesn’t know how polluted the air was.
For example, you could run the purifier non-stop for 3 months in the Swiss Alps, and it would still tell you to change the filter, even though it wasn’t exposed to air pollution.
Keep in mind, that companies need to make revenue. The more often you buy replacement filters, the better for them.
From my experience, a standard HEPA filter lasts longer than recommended.
A good way to check its remaining lifespan is by using a separate air quality monitor in the room. When you notice that the air isn’t getting clean anymore, that’s probably a sign it’s time to get a new filter.
Auto Mode Settings
Many air purifiers come with an auto mode. This mode automatically turns on the purifier when the built-in reader detects poor air quality. Once the sensor thinks the air improved, it reduces the fan speed again.
However, remember that the built-in PM2.5 sensors in air purifiers aren’t very accurate. This means that the auto mode might not be reliable. Tests have shown that auto mode often doesn’t reduce indoor air pollution to safe levels.
So, it’s better to use your air purifier in manual mode. You can keep track of air quality using an external sensor, as mentioned earlier.
Almost all air purifiers come with at least three fan speed settings. Being able to adjust the fan speed is crucial because when air pollution levels are high, you should set your air purifier to its highest speed.
Some air purifiers include a remote control, but I’ve never found the need to use them. While I don’t think they’re essential, others might find them useful.
Wi-Fi Capabilities and Smart Home Integration
Modern air purifiers often come with WiFi and can be managed using an app.
I don’t have any air purifiers with an app, and I can tell that air purifiers work just fine without them. But there were times, especially at night, when I wished I could adjust the fan speed with my phone without having to get out of bed.
Portability Features (Handles, Wheels)
Most air cleaners are lightweight, weighing just a few kilograms, and are easy to move around.
Keep in mind that air purifiers can be knocked over easily, especially by kids. If you have toddlers around, make sure to place the purifier where they can’t reach it.
Or check out the Sqair air purifier. Thanks to its four-leg design, it’s pretty tip-resistant.
Also, there are larger and heavier models available. If you’re considering an air purifier that weighs over 10 kilograms, it’s a good idea to see if it has lockable wheels like the Blast air purifier.
Having wheels is handy if you want to rearrange your room, as it makes moving the air purifier much easier.
Maintenance and Upkeep
Fantastic, if you came to this point, you are already pretty much familiar with everything important.
Now, let’s move on to talk about maintenance and how to take care of things.
When choosing an air purifier, consider the frequency and cost of replacing filters, as this can be a significant ongoing expense.
Regular cleaning, especially of the pre-filter, is essential for maintenance. Evaluate the cost-effectiveness of air purifiers by comparing their CADR rating to the price, ensuring you get the most clean air for your money.
Before choosing an air purifier, inform yourself about its replacement filters. Get info on:
Air purifiers require regular filter replacements that can turn out to be costly if you pick an air purifier brand that charges a lot for replacement filters.
General Cleaning Guidelines
Air purifiers are sturdy and don’t need a lot of maintenance.
The main thing to do is to regularly clean the pre-filter. This filter catches big dust particles that can’t get through the HEPA filter and would just clog it up.
Cleaning the pre-filter once a month is usually enough.
If your air purifier doesn’t have a pre-filter, no problem. Just gently clean the dust off the HEPA filter. You can do this by wiping it or tapping it out on the balcony or over the sink/bathtub.
Let’s head to the most sensitive topic: the costs of air purifiers
Air purifiers can vary greatly in price, often influenced by additional features that do not necessarily improve air cleaning efficiency.
To assess value for money, compare the CADR rating to the price, aiming for more clean air per dollar spent. Consider ongoing costs, particularly regular filter replacements, which are necessary and recurring expenses.
Understanding Pricing and Value
Lots of air purifier brands charge a lot, sometimes hundreds or even thousands of dollars, for their products.
Sure, they might look cool, with great features, fancy LED lights, and a slick app.
But I want to be clear with you: all these extra features don’t mean you get more clean air.
What they do mean is a higher price tag.
At the end of the day, an air purifier is mostly just fans and filters. This is a basic and inexpensive technology. But big brands add all these extras and patents to make their products seem more valuable and justify the high prices.
If you’re on a tight budget, don’t worry. There are plenty of effective air purifiers that are affordable.
A good way to compare them is by looking at their CADR ratings and how they stack up against the price.
A simple way to check an air purifier’s value for money is to calculate how much clean air you get for each dollar spent. It’s an easy calculation.
Just divide the CADR rating (in m³/hr) by the price. This gives you the amount of clean air (in m³) you get for each dollar. The higher this number, the more cost-effective the air purifier is.
For example, if an air purifier has a CADR of 350 and costs $179, divide 350 by 179. You get 1.96.
This means the air purifier gives you 1.96 cubic meters of clean air for every dollar you spend.
Do this calculation for any air purifier you’re considering, and you’ll find the best value for your money.
Ongoing Costs and Maintenance Expenses
As I said earlier, air purifiers need their filters replaced regularly. Most of them need a new filter twice a year. But if you’re in a place with less pollution, changing it once a year should be enough.
Just check that the cost of new filters fits your budget.
A reasonable price for HEPA replacement filters for a typical home air purifier is between $30 and $50.
Making the Right Choice When Picking an Air Purifier
Great, you’ve made it to the end of our guide on buying air purifiers.
Now, you’ve got all the info you need to choose the right air purifier without getting swayed by brands, marketing, or price.
Below, I’ve put together a checklist that covers the key things to think about when picking the best air purifier for you.
Air Purifier Buyer Checklist
Choosing the right air purifier is crucial for maintaining healthy indoor air quality, especially in environments with high pollution levels or for individuals with specific health concerns like allergies or asthma.
The key is to select a model that effectively addresses your specific needs, whether it’s combating fine dust, allergens, smoke, or chemical pollutants.
Remember, the most expensive model isn’t always the best; focus on essential features like HEPA filtration, room size compatibility, CADR rating, noise, and energy efficiency.
Regular maintenance and understanding the ongoing costs are also vital for long-term satisfaction with your air purifier.
Karl von Luckwald
Since moving to Thailand in 2019, Karl noticed the lack of scientific integrity in air purifier and water filter reviews. In response, he founded WE DO AIR to champion unbiased, science-based evaluations and empower consumers to make better-informed decisions.