Fan intakes on non-purifying Dyson do get plugged with dust over time, so it makes sense to add filters. Aside from whether it makes sense to advertise them as air purifiers.
That makes me wonder if that was how the product originated. Dyson realizes its fans have a problem. Engineers suggest an air filter. Marketing see an opportunity.
The Dyson marketing person's angle is a sleight of hand:
"Dyson has developed its own testing methodology, the POLAR test method, which, unlike the CADR, Hill said, "measures the intelligence of the purifier, the ability for it to know when that room is clean or dirty and automatically react, and its ability to mix that pure air around the room."
The detection function seems of spurious value if the device is operating at max capacity regardless of whether a pollutant is detected or not.
Is that the case, or does the Dyson adjust volumetric flow to match the detected level of pollutants? That would make sense in the case of smoke, although humans could detect smoke and turn the device on or off accordingly.
COVID19 particles are a different case. If the Dyson can detect those and switch itself on, eliminating the virus from the room, $800 is a bargain. But it can't.
