We are working on the LEED project in Korea.

I have a question about ASHRAE 62.1 2010.
Section says, "When the building is located in an area where the national standard or guidelines for PM2.51 is exhausted, particle filters or air cleaning devices shall be provided to clean the outdoor organization."

It's stated as. What does the National Standard mean here? Are you telling me to follow Korea's PM2.5 standard? If there are no national standards, what standards should I follow? There is no standard for PM2.5 in Korea in the EPA standards.