Under the Asbestos Hazard Emergency Response Act (AHERA), are five transmission electron microscopy (TEM) outside air samples required to be collected with the five inside and the two blanks if the inside samples and blanks are below 70 structures/mm2?

The five outdoor samples must be collected in addition to the five indoor samples, the two field blanks, and the one sealed blank for a total of thirteen air samples. (40 CFR part 763.90(i)(3)) If the five inside samples are below 70 structures/mm2 and the volume of air used for the samples is equal to or greater than 1,199 L of air for a 25 mm filter, or greater than or equal to 2,799 L of air for a 37 mm filter, then according to 40 CFR part 763.90(i)(4), regardless of the statistical comparison between the indoor and outdoor samples, the response action is considered complete.