Measurements for PM, NO2 and CO and readings interpretation

I noticed that NO2/CO eggs give high readings for NO2 and CO (over 1600, 70 respectively) and take around 20 minutes to stabilize at normal levels.
Question: what is the technical explanation for this behaviour? Can it be avoided?

for the PM egg, what is the interpretation of the PM reading on the device in terms of PM10 and PM2.5? A weighted combination? what ratios?