Start with what the machine has to move
Every purifier on this list is judged first on how much air it can shift, and the spread is wide. AlorAir leads on paper with a clean air delivery rate of 1,274.25, followed by AirDoctor at 944.64 and Air Health at 713.58. Alen Air Purifiers sits at 637.125 and Airthereal at 319.41, while AirDoctor Europe lists a range of 162 to 336 because its models differ.
That single number tells you how fast a room clears, so match it to the space you actually clean rather than the largest figure available. You can see where each brand lands in our air purifiers ranking.
Room coverage is the number most people should use
Clean air delivery rate means little on its own, so convert it to a floor area. AlorAir covers 306.58 and Air Health covers 297.29, which suits open-plan living spaces and loft conversions. Alen Air Purifiers claims 260.13, and Airthereal 185 fits a mid-sized room.
AirDoctor is the sharpest contrast here. Its stated coverage is 96.9, so it is a bedroom or small office machine rather than a whole-floor solution, even though its delivery rate is high. AirDoctor Europe varies by model, with coverage of 113 to 225. Measure the room first, then read the AirDoctor review and the Air Health review against your floor area.
Filter costs and how often you touch them
Filter replacement is the biggest running cost, and the interval tells you how often that cost arrives. Alen Air Purifiers has the longest interval at 12 to 15 months, followed by Airthereal at 6 to 8 months and Air Health at 6 months.
AirDoctor and AirDoctor Europe both list intervals of 6 to 12 months and 6 to 12 months, which means the same machine can behave differently depending on how you run it. A shorter interval usually means a higher filter grade, so treat the two together. Our Alen Air Purifiers review covers the ownership side in more detail.
Noise, power draw and what you hear at night
Bedroom use is decided by the quietest setting. Air Health and Airthereal both drop to 22 and 22 on their lowest speed, and Alen Air Purifiers to 25. Those are the picks for a sleeping room.
The rest are louder at minimum, with AirDoctor Europe at 39 and AlorAir at 50. Power draw follows a similar pattern: Alen Air Purifiers runs as low as 1.36 to 55 and AirDoctor Europe as low as 11 to 95, while Air Health draws 10 to 50. A machine that moves more air also pulls more power, so check the low end before choosing a low-output model for a bedroom.
Apps and hands-free control
An app is the feature that separates connected brands from standalone units. Air Health, Airthereal, Alen Air Purifiers, AlorAir and Alorair the dry air all ship with a mobile app, so you can check readings and change settings from your phone.
AirDoctor Europe is the exception: it has no mobile app, which is worth knowing if remote control matters to you. Its air change rate of 162 to 336 still makes it a capable purifier, but you operate it from the panel. Compare the options in the AirDoctor Europe review before ruling it out.
Warranty length as a reliability signal
Warranty length is the closest thing to a reliability statement these brands make. Air Health leads with 10 years, AlorAir follows at 6 years, and Airthereal and AirDoctor Europe both offer 2 years.
AirDoctor and Alen Air Purifiers sit lower at 1 year and 1 year. A short warranty does not mean a unit will fail, so weigh it against filter life and the coverage area you need. For dehumidifying models rather than purifiers, see our dehumidifiers ranking.
Specialist jobs: extraction and combined units
Some devices do more than purify. AlorAir handles extraction as well, pulling 56.78 in a day, and it pairs that with a clean air delivery rate of 1,274.25. If you have a damp or musty space, that combination matters more than a higher purifier figure.
Airthereal also sells combined machines, and its water tank of 1.5 on the Ethereal Rain shows the humidifying side of that range. Alorair the dry air focuses on drying rather than filtering, so treat it as a different category entirely. The Airthereal review walks through both purifier and combo models.
How to put the numbers together
Start with room area, because that sets the clean air delivery rate you actually need. Then check the quietest noise figure if the unit runs in a bedroom, and the filter interval against the yearly cost of replacements. Add the app only if you want phone control, and read the warranty as a background reassurance rather than a deciding factor.
That order stops you buying a high-output machine for a small room, or a quiet bedroom unit that cannot handle a large living space. When you have narrowed it down, the individual brand reviews linked above go into the specifics for each one.