(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.