I work in the environmental air quality field, so indoor air quality is super important to me.  I'm also an allergy sufferer, which makes it even more important.  Very happy with the fact that this unit displays the PM2.5 concentrations in the room air.  We know it's working when the furniture (two lounge chairs) around the unit are moved/re-arranged and the PM2.5 concentration display value increases because we're stirring up dust.  Also appreciate that when the unit does detect higher concentrations of particulate, the fan will kick into a higher speed and filter until levels are reduced again.  Very happy!