The wife has severe asthma, so we run two purifiers, one Altec Pro 1 and one Altec AL3. They are both automatic and sample air quality and adjust function accordingly. Two things I am aware of: If you set the units side by side and turn them on the automatic function settings, the AL3 will come up with consistently poorer air quality levels and turn itself on higher function modes than the Pro 1, in fact the Pro 1 hardy ever turns itself up to a higher function level. We took a video of the two machines working side by side and then sent the Pro 1 back to the factory on their recommendations after talking to them on the phone. At first they said it was defective and they would send us a replacement, then they sent us our old unit back and when we called them they said they could find nothing wrong with it. The other thing is that we have been trying to buy a new filter for the smaller AL3 unit for nearly one year, I ordered it on Lazada six times only to have the seller cancel the order because they do not have it. Currently we have been waiting for a call back from Altec for nearly three weeks. I am not degrading the company, just stating facts.