Spike in PM2.5

My monitor is showing a 4 hour spike in PM2.5 in the middle of the night. It goes from being steadily in the green (around 30) then at 2:00 am shoots up to 117 and by 6:00 am is back to normal. Could this be an error?

Hi Lane,

Have a look at the graph for your monitor to see if both channels showed an increase in particles over that time period. If so there is high confidence the readings are not in error.

Consider the wind direction and compare your readings to other nearby monitors to see if they went up during the same period to determine if your readings might be due to a localized source.

Ventilation rates generally drop at night because of less wind and mixing, and a temperature inversion could set up, so air pollution could build up over night at ground level.