17.8.212 AMBIENT AIR QUALITY STANDARDS FOR CARBON MONOXIDE
(1) No person shall cause or contribute to concentrations of carbon monoxide in the ambient air which exceed any of the following standards:
(a) Hourly average: 23 ppm, hourly average, not to be exceeded more than once per year.
(b) Eight-hour average: 9 ppm, eight-hour average, not to be exceeded more than once per year.
(2) Measurement method: For determining compliance with this rule, carbon monoxide shall be measured by the nondispersive infrared method, as more fully described in 40 CFR Part 50, Appendix C (1979), or by an approved equivalent method.