The dust level in one room of my house reached 3.5 million particles per cubic meter, where the particles were detected at a size of less than two microns (with some potentially as small as 500 nanometers) – using a Dylos 1100 (“Pro” version) electronic particle detector. I have several detectors of various sorts. Often, the alarm on one of them is triggered in the middle of the night. The other detectors do not have audible alarms. In search of the cause of huge night-time spikes in the level of particulates, I used an IR camera to take shots of the affected room.
A Storm Of Photons 