Dust sensor with mass separation fluid channels and fan control

A particulate matter (PM) sensor, comprising:

• a mass separation fluid tunnel body defining a fluid inflow channel, a first fluid channel branch opening off of the inflow channel and having a first outlet, a second fluid channel branch opening off of the inflow channel and having a second outlet, and a fluid port between the first fluid channel branch and the second fluid channel branch;
• a fan located downstream of the first outlet and the second outlet;
• a laser diode;
• a photodetector located in the first fluid channel branch;
• and
• a computing device coupled to the photodetector having a processor and a memory storing instructions which, when executed by the processor, determines a mass concentration of particles in the first fluid channel branch based on an output of the photodetector, where the output of the photodetector is based on detecting light emitted by the laser diode scattered by dust particles present in a fluid flow through the first fluid channel branch.