Ariz. Admin. Code § R11-1-427
Diesel engines must not be operated when the atmosphere adjacent to its engine contains toxic gases above the tolerance set by the United States Bureau of Mines as listed below:
| Carbon dioxide | 0.5% | by vol. |
| Carbon monoxide | 0.01% | by vol. |
| Nitrogen dioxide | 0.0005% | by vol. |
| Oxygen must be at least | 19.5% | by vol. |
Former Rule 4:27; Amended effective August 18, 1980 (Supp. 80-4).