Cal. Code Regs. tit. 17 § 70100 : Public Health — Air Resources — Air Resources Board — Air Basins and Air Quality Standards — Ambient Air Quality Standards — Definitions

(a) Ambient Air Quality Standards. Ambient air quality standards are specified concentrations and durations of air pollutants which reflect the relationship between the intensity and composition of pollution to undesirable effects.
(b) Most Relevant Effects. "Most Relevant Effects," shown in the Table of Ambient Air Quality Standards, are the effects which the standards are intended to prevent or abate.
(c) Parts Per Million (ppm). Parts per million is a volumetric unit of gas concentration, which is numerically equal to the volume of a gaseous contaminant present in one million volumes of air.
(d) Micrograms Per Cubic Meter (ug/m3). Micrograms per cubic meter is a unit of concentration which is numerically equal to the mass of a contaminant (in micrograms) present in a one cubic meter sample of air, measured at EPA reference conditions (corrected to 25 degrees Celsius, 760 torr). ( 40 CFR Part 50.3, November 25, 1971).
(e) Equivalent Method. "Equivalent Method" is any procedure for measuring the concentration of a contaminant, other than that specified in the air quality standard for the contaminant, which can be shown to the satisfaction of the Air Resources Board to give equivalent results at or near the level of the air quality standard.
(f) Visual Range. "Visual Range" is the distance at which a black object on the horizon has a 2 percent contrast with the horizon sky. This dis- tance can be calculated from a measured light extinction coefficient, Bext., by the formula: V r = 3.912 divided by Bext. = 3.912 divided by Bext.
(g) Carbon Monoxide (CO). Carbon Monoxide is a colorless gas, odorless under atmospheric conditions, having the molecular form CO.
(h) Sulfur Dioxide (SO 2). Sulfur dioxide is a colorless, irritating gas under atmospheric conditions, having the molecular form SO 2.
(i) Suspended Particulate Matter (PM10). Suspended particulate matter (PM10) refers to atmospheric particles, solid and liquid, except uncombined water as measured by a (PM10) sampler which collects 50 percent of all particles of 10 mm aerodynamic diameter and which collects a declining fraction of particles as their diameter increases and an increasing fraction of particles as their diameter decreases, reflecting the characteristics of lung deposition.
(j) Fine Suspended Particulate Matter (PM2.5). Fine suspended particulate matter (PM2.5) refers to suspended atmospheric particles solid and liquid, except uncombined water as measured by a PM2.5 sampler which collects 50 percent of all particles of 2.5 mm aerodynamic diameter and which collects a declining fraction of particles as their diameter increases and an increasing fraction of particles as their diameter decreases, reflecting the characteristics of lung deposition.
(k) Visibility Reducing Particles. Visibility reducing particles are atmospheric particles which significantly scatter or absorb light. The effect of these particles on light extinction is to be determined by instrumental monitoring of light scattering and absorption by ARB Method V, as adopted August 18, 1989, or by an equivalent method.
(l) Hydrogen Sulfide (H 2 S). Hydrogen sulfide is a colorless gas having the molecular form H 2 S.
(m) Nitrogen Dioxide (NO 2). Nitrogen dioxide is a red-brown gas, odorless under atmospheric conditions, having the molecular form NO 2.
(n) Lead (particulate). Lead (particulate) is suspended particulate matter containing lead (Pb).
(o) Sulfates. Sulfates are the water soluble fraction of suspended particulate matter (PM10) containing the sulfate ion (SO 4 2-) including but not limited to strong acids and sulfate salts, as measured by MLD Method 007 (based on high-volume size-selective inlet (SSI) sampling and ion chromatography), dated January 19, 1988. ) including but not limited to strong acids and sulfate salts, as measured by MLD Method 007 (based on high-volume size-selective inlet (SSI) sampling and ion chromatography), dated January 19, 1988.
(p) Vinyl Chloride. Vinyl chloride is a colorless gas with the molecular form CH 2 -CHCl; chloroethene.
(q) Ozone. Ozone is a colorless gas with a pungent odor, having the molecular form O 3.
(r) Extinction Coefficient. The "Extinction Coefficient" of a homogenous air mass is the natural logarithm of the fractional transmission of a beam of light per kilometer along the beam's path.

Cal. Code Regs. Tit. 17, § 70100

Note: Authority cited: Sections 39600, 39601 and 39606, Health and Safety Code. Reference: Sections 39602 and 39606, Health and Safety Code.

1. New section filed 12-22-69; effective thirtieth day thereafter (Register 69, No. 52).
2. Repealer and new section filed 1-27-71; effective thirtieth day thereafter (Register 71, No. 5).
3. Amendment of Note filed 3-18-77; effective thirtieth day thereafter (Register 77, No. 12).
4. Amendment of subsection (j) filed 7-20-83; effective thirtieth day thereafter (Register 83, No. 30).
5. Amendment of subsection (i) filed 9-5-84; effective thirtieth day thereafter (Register 84, No. 36).
6. Amendment filed 11-27-85; effective thirtieth day thereafter (Register 85, No. 48).
7. Amendment filed 3-28-86; effective thirtieth day thereafter (Register 86, No. 13).
8. New subsection (r) filed 6-28-88; effective 7-28-88 (Register 88, No. 27).
9. Amendment of subsections (f) and (l) and new subsection (s) filed 9-18-89; operative 10-18-89 (Register 89, No. 39).
10. Amendment of subsection (k) filed 6-29-92; operative 7-29-92 (Register 92, No. 27).
11. Amendment of subsections (d), (j), (k), (p) and (q) and amendment of Note filed 6-5-2003; operative 7-5-2003 (Register 2003, No. 23).
12. Repealer of subsection (g), subsection relettering and amendment of newly designated subsections (i) and (j) filed 4-17-2006; operative 5-17-2006 (Register 2006, No. 16).