Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Lowest and highest concentrations that can be measured, in principle, using passive diffusion tubes for an exposure period of 168 hours (one week).
| Contaminant | Lowest value ppm |
Highest value ppm |
|---|---|---|
| CO | 0.3 | 6 |
| H2S | 0.06 | 1.2 |
| NO2 | 0.006 | 0.18 |
| SO2 | 0.01 | 0.60 |
| benzene | 0.12 | 3.0 |
