Comparison: The best air purifier 2021 

In times of COVID-19 and long hours spent at the home office, portable air purifiers are ideal for improving indoor air quality. However, there are several important criteria to consider before making a purchase because of the fact that not every air purifier is suitable for all needs.
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Polluted indoor air leads to long-term health damage such as asthma and reduced lung function. However, not only pollutants but also the viruses & bacteria transmitted to humans through aerosols can significantly affect our health and lead to illness. In addition, poor air quality has a negative impact on concentration and productivity even after a short time.

The solution against polluted indoor air is simple: air purifiers. In this article, we will give you an overview of the most common indoor air pollutants and their impact on our health. Then, we will compare which air purifier is the best portable air purifier 2021 based on the following criteria:

  • Filter technology
  • Energy consumption
  • Noise level
  • Filter performance
  • Size of filtered pollutants
  • Room size
  • Intelligent sensor technology
  • Design and ease of use
  • Cost of filter replacement
Fact: Our indoor air can be up to 5 times more polluted than outdoor air.

(U.S. Environmental Protection Agency)

Typical indoor air pollutants

Most pollutants in indoor air are invisible and can, for example, enter the room through window ventilation (fine dust, nitrogen oxides, etc.). In addition, air pollutants can also be generated by sources within the room itself: Activities such as smoking, cooking, and heating can lead to a deterioration in air quality. Also, cleaning products, off-gassing from furniture & textiles, and mold growth can pollute the air. While air pollutants disperse and dilute outdoors, they tend to accumulate continuously indoors. The less often the air is cleaned, the more harmful it becomes to your health due to the increasing concentration of pollutants.

Viruses & Bacteria

Viruses and bacteria pose a major health threat and are therefore of high importance when it comes to air quality. Viruses, for example, can be transmitted to humans via aerosols in the air and lead to infection.

Mold spores

When indoors, mold multiplies on damp surfaces such as heating and air conditioning systems, cold bridges on windows, or even behind furniture placed too close to the wall which prevents the air from circulating sufficiently.

Dander from pets

Cats and dogs are common sources of indoor allergens released by secretions, excretions, and dander.

Ultrafine Particulate Matter

Unlike inhaling PM10 and PM2.5, ultrafine particles (UFP) are released by vacuum cleaners and car exhaust among other sources, and cause a variety of problems in our bodies.


Pollen is a fine powdery substance, typically yellow in color, consisting of pollen grains that are carried through the air. They can trigger allergies such as hay fever, which is accompanied by sneezing, runny nose, and itching eyes. The most common types of pollen include trees such as birch, grasses, and herbs.

Volatile organic compounds (VOCs)

Volatile organic compounds are gases and chemicals released by paints, furniture, and during the use of cleaning agents.

House dust mites

House dust mites are hardly visible due to their very small size and transparent body. Their excretions can cause allergic reactions. The symptoms range from itching, breathing difficulties to asthma.

Health consequences due to air pollutants

The health effects of pollutants in the air depend on the duration and concentration of the pollution. The longer and the higher the concentration of pollutants in the air we breathe, the more harmful it is for us. The most common health problems caused by air pollution include mild symptoms such as:

  • Fatigue
  • Headache
  • Irritation of the eyes
  • scratching in the lungs
  • itching of the skin
  • Dizziness
  • Irritation of mucous membranes
  • Circulatory problems

Serious symptoms and long-term consequences can include:

  • Loss of lung capacity and decreased lung function
  • Skin aging, pigmentation spots, skin irritation, eczema
  • Hypertension, cardiovascular disease, nervous system damage
  • Respiratory diseases such as asthma, bronchitis, emphysema and cancer

Why do I need an air purifier?

Like food and water, air is essential for our survival. You breathe about 17,000 times a day, inhaling about 120,000 liters of air. But how often do you think about the cleanliness of the air you breathe in every day? 

In many parts of the world, the concentration of pollutants has increased significantly. As previously mentioned, this increased pollution can lead to various health problems. However, air purifiers can filter many pollutants, lowering the risk of health problems and improve your well-being, productivity, and concentration.

What makes the best air purifier 2021?

When buying an air purifier, the goal is simple: To improve the air quality at home or in the office. But when you start comparing different air purifiers, you quickly lose track of technical specifications, costs, filter types, and energy consumption. This makes choosing the right device much more difficult. We have therefore compiled a list of the most important criteria that will help find the right air purifier for you:

Filter technology

There are numerous different filter technologies on the market that are used for air purifiers. Below is an overview of the most important technologies

a) HEPA Filter

HEPA filters consist of a mesh that resembles a net. Particles are captured by the mesh as the air passes through. HEPA filters can effectively filter larger particles such as pet dander, pollen, and dust mites. However, VOCs, viruses, bacteria, and small particles under 0.3 microns cannot be safely removed from the air with a HEPA-based air purifier. This type of filter was developed in the 1940s as part of the Manhattan Project to remove dangerous radioactive particles from indoor air.

b) PECO Filter

In PECO filters, ultraviolet A-light is irradiated onto a filter membrane coated with nanoparticles. This creates a photoelectrochemical reaction on the surface of the filter that breaks down the molecular structure of organic particles in the air. 

c) Ionizer

In a filter with ionization, ions are positively charged so that dust particles in the air attach to them.  Through their electrostatic interaction, several particles finally form a cluster. These clusters can then be filtered more easily by the air purifier. However, this produces ozone, which is also harmful to health.

d) Plasma Filter

Air purifiers with plasma filters have the ability to capture even the smallest particles that other types of filters cannot capture. A plasma purifier generates ions that electrically charge air pollutants within the air cleaner so that they can be separated in the subsequent collector. In this way, pollutants as small as 0.01 micrometers can be removed from the air. Despite their high efficiency, no measurable ozone is produced.

Energy Consumption

Depending on the mode set and how long the air purifier is used, the kilowatt-hours consumed can quickly add up, especially if it runs continuously. Therefore, a comparison of the data regarding power consumption is useful. Here you can orientate yourself on the consumption of a 6-9 watt LED lamp, which leads to approximate electricity costs of 2.50 € per year.

Noise Level

If an air purifier is too noisy, you probably won’t use it very often. . The quietest air purifiers on the market have a dB value of 20-40, but it should be noted that the noise level of an air purifier changes depending on the fan setting.

  • 30 dB corresponds approximately to the noise level of a whispered conversation
  • 50 dB corresponds to a normal conversation or a moderate rain shower
  • 70 dB is as loud as a vacuum cleaner

Filter Performance

The CADR value (CADR stands for Clean Air Delivery Rate) indicates how much room air is cleaned from three different types of particles, each with a size between 0.09 µm and 11.0 µm, within one minute. It is often used to directly compare air purifiers with each other. However, it should be noted that the filter performance of very small particles, which includes fine dust, for example, is not taken into account when determining this value. Likewise, the value provides no information about the neutralization of odors or volatile organic compounds (VOCs).

Size of Pollutants

The smaller the pollutants, the more dangerous they are for our bodies. The smallest particles can reach deep into the lungs and bloodstream. Studies show that pollutants as small as 2.5 micrometers in diameter, such as smoke, particulate matter, and bacteria have negative health effects over long periods of time (years) and can increase the risk of severe asthma attacks. The different air pollutants can be divided as below:

  • Ultrafine particles (<PM1)
    They have a diameter of 1.0 micrometer or less. The most common types are bacteria and viruses. For example, a COVID-19 virus has a size of 0.12-0.16 micrometers.

  • Fine dust particles (<PM2.5).
    They have a size of 2.5 micrometers or less. They include fine dust, smoke caused by cigarettes, but also forest and bush fires, animal hair, and bacteria.

  • Pollutant particles (<PM10)
    Their diameter is 10 micrometers or less. Common types are dust, pollen, and mold spores.

Room Size

Before purchasing an air purifier, the size of the room in which the air will be filtered should also be taken into account. Depending on the model, filters can provide purified air for small to large rooms.

Intelligent sensor technology

There are devices with adjustable modes that allow you to run the air purifier at the speed you want. Ideally, this should be possible via an app. Some air purifiers also have a sensor that detects the level of pollution and automatically adjusts the speed of the fans as needed to neutralize the potentially harmful particles suspended in the air. Since not only indoor air quality but also outdoor air pollution plays an important role in our health, this data ideally should also be evaluated by air purifiers. By analyzing this data, the air purifier can warn, for example, when increased pollen counts are present or high levels of pollutants in the air due to forest fires are imminent.

Design and usability

Many things such as aesthetics, portability, ease of setup, and wifi accessibility are included in this aspect. Ideally, the air purifier should match the interior design of the room. However, not only the design itself matters, but also the materials used for this purpose. Meanwhile, an increasing number of manufacturers are turning to recycled plastic and bamboo for this very reason.

Costs for filter exchange

For the majority of air purifiers, costs for filter replacements must be regularly calculated. Filter life can range from a few months to a year, depending on the level of pollutants in the home and the type of filter technology in the unit. Ideally, however, you should choose an air purifier that does not require filter replacement. This not only saves costs but also protects the environment at the same time, as many of the filter units cannot be degraded sustainably.

Comparison: The best air purifier 2021

We have applied the described selection criteria to the most interesting portable air purifiers on the market to help you decide which air purifier best suits you and your needs.

OneLife X Molekule Air mini Dyson Pure Cool TP02
Filter Technology Plasma PECO HEPA
Energy Consumption 8W 68W 56W
Annual electricity costs $6 $60 $49
Volume at the highest level 22-55 dB 39-62 dB 63 dB
Size of Pollutants Up to 0,01μm Not published Up to 0,1μm
Room size 270 sq ft 250 sq ft 400 sq ft
Intelligent sensor technology & app
Sustainable materials X X
Filter exchange costs per year $0 $135 $73
Size (H x W x D) 15.95 x 7.48 x 7.48 inches 12 x 8.27 inches 8.82 x 45.28 x 8.62 inches
Weight 8.8 lbs 7.28 lbs 8.25 lbs


Each of the presented air purifiers provide improved air quality and thus have a positive impact on your health. However, due to the different filter technologies, the performance and the size of the particles that can be filtered differ accordingly. 

It should be noted that an air purifier should filter at least particles up to a size of 0.1 micrometers. However, filters that capture even particles as small as 0.01 microns are better. This includes ultra-fine dust and viruses, which can reach deep into the lungs, bloodstream and brain, where they can trigger health-threatening situations. 

The comparison also shows that it is worth taking a look at the energy requirements of the air purifier. Here you can find significant differences between the manufacturers.

Air purifiers improve air quality and our health, but this should not be done at the expense of our environment. Traditional technologies such as HEPA and PECO require regular filter changes, which cause high additional costs and large amounts of waste. Sustainable air purifiers, like the OneLife X, do not require filter changes, saving the environment and your wallet.

The appearance of the air purifier also plays an important role. While most manufacturers produce the housing from synthetic materials and plastic, there are now also alternatives that rely on natural materials such as bamboo. 

It remains to be said: It is not possible to choose an overall winner across the board as ‘ requirements for each device are too individual. You can take a look at which of the listed criteria are particularly important to you in order to find the best air purifier for you. For example, if you place a lot of importance on  great filter performance, sustainable design and the volume of the air purifier, the OneLife X is the right choice for you.