And how many micrograms was the test returning? 

Results showed .22 micrograms in the unit done at the furnace and the other unit done at the return air came back as 2.24 micrograms.

If you decide to sell later, the end buyer may do another test and it may actually be higher than 1.0 micrograms per 100 square centimeters.  

The known bad samples show an average of 5.24 micrograms of H2S per kilogram of drywall and no detectable H2S in the known good drywall (detection limit is 0.28 micrograms/Kg).

The primary endpoint will test whether a 100-microgram dose of the vaccine prevents symptomatic COVID-19 disease.

"above the current CDPHE 6 CCR 1014-3 regulation clearance level of one-half microgram  methamphetamine per one hundred square centimeters (0.5μg/100cm2)...remedial operations are necessary.  

HUD lowered the floor from 40 micrograms/SQFT to 10, window sills from 250 to 100 and window troughs 400 to 100.Now, we see senator Portman who is a hard core conservative republican join others, including democrats, on this issue.For those who think that dust wipes ought to be omitted from the Toledo Ordinance, Portman's new regulation assures that dust wipes are necessary and visual inspection as is, is now obsolete."

However, the trigger events for this have become easier to have occur (they lowered the required lead level from 10 micrograms per Liter to 7.5 micrograms per Liter in a child's blood) and universal screening was implemented, causing the number of tests to go up. 

California is yet to update it's meth clean up page, but it does seem to contain a contamination level of 1.5 micrograms per 100 square centimeters as a standard for presumably the max amount of residual methamphetamine.https://www.dtsc.ca.gov/SiteCleanup/ERP/Clan_Labs....For cleanup, there are lots of other state sites, e.g.

It’s a sticky strip and it’s measured in micrograms.