Philips AC2210

How much clean air the purifier delivers an hour, measured with smoke, dust and pollen. A higher figure cleans a bigger room or the same room faster.

The test the CADR comes from. AHAM AC-1 and the DOE test are independent and comparable. A maker's own test is not.

The room size where the purifier changes the air 4.8 times an hour under a 2.5 m ceiling, worked out from its CADR. We use it so every model is compared on the same rule.

The room size the maker states. Makers use different rules, so we show it but never rank on it.

Whether the particle and carbon layers are one filter or separate ones. Separate filters let you replace only the part that is spent.

A filter of activated carbon that takes out smells and some gases. It does not catch particles.

How many filters the purifier holds, each a part to replace.

A coarse mesh in front of the main filter that catches hair and fluff. A separate washable one is rinsed under the tap, which keeps the expensive filter from clogging early.

How the purifier tells you the filter is due. A timer counts the hours it has run, a sensor judges the filter itself, an estimate weighs the hours against the air it cleaned, and a plain indicator is one the maker does not explain.

How long the maker says a filter lasts, in months of normal use. A filter that is spent cleans less.

What the filters cost over a year, at the lowest shop price for each filter today and the filter life the maker states. It moves with the shop prices.

The sound level at the lowest speed, as the maker measures it.

The sound level at the highest speed, as the maker measures it.

The power the purifier draws at its highest speed.

How many speeds you can choose by hand, the automatic mode not counted.

What the purifier measures in the air. A particle sensor lets it speed up and slow down by itself.

What the unit itself shows of the air it measures: a figure, such as the PM2.5 level, or only a coloured light.

The fan speed follows the air quality the sensor reads.

The settings the maker names besides plain fan speeds, such as a quiet sleep mode or a timer.

A sensor that dims the lights and display when the room goes dark.

Whether you can control the purifier from a phone app, over wifi or only nearby over Bluetooth.

Which voice assistants the robot works with, such as Google Assistant or Alexa.

Matter is the standard that lets devices from different makers work together. With it you can run the robot outside the maker’s own app. On this model: Assumed, not a stated fact: the maker's full specification does not name it, so we take it as no.

Locks the buttons, so a child or a pet cannot change the settings or switch it off.

A remote in the box, for changing the speed without getting up or opening an app. On this model: Assumed, not a stated fact: the maker's full specification does not name it, so we take it as no.

What the purifier weighs. It counts most if you move it from room to room.

An ioniser charges particles so they stick to walls and furniture instead of the filter, and some come loose again later. Some also make ozone, which irritates the airways and can turn scents in the room into formaldehyde. That is why a switch to turn it off matters.

Whether the purifier is said to make no ozone. UL 2998 is an independent test that it gives off next to none, a maker's claim is the maker's word alone.

The warranty the maker gives in the Netherlands. Consumer law here stands apart from it and can last longer.