Daily Maximum Eight-Hour Ozone Averages for February 2021

The table below lists the peak daily maximum eight-hour ozone concentrations measured in February 2021 in each community where the DAQ measures ozone. Concentrations that are rated Moderate or higher are color-highlighted based on the EPA-defined Air Quality Index colors. (See Interpreting the AQI.) All ozone measurements are in parts per billion.

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Month:	Year:	Report Format:	Include time:
			Include time
Highlight with AQI colors

Area	Monitoring Site	POC	February 2021																								POC	Monitoring Site
Area	Monitoring Site	POC	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	POC	Monitoring Site
Clark County
	Virgin Valley	1 ^N	28	31	39	40	37	41	37	34	38	46	40	44	39	41	37	NV	41	43	43	43	41	42	38	23	1	Virgin Valley
	Paul Meyer	1	28	28	44	42	36	40	36	29	32	NV	40	40	45	43	36	44	42	41	37	43	41	40	36	18	1	Paul Meyer
	Mountains Edge	1	30	32	43	44	42	42	39	29	30	45	42	41	45	44	35	45	44	42	NV	45	43	39	41	29	1	Mountains Edge
	Walter Johnson	1	31	34	50	47	40	44	40	34	38	45	40	42	47	46	42	47	46	44	38	47	45	41	44	27	1	Walter Johnson
	Palo Verde	1	33	34	50	46	40	42	39	36	39	44	41	41	45	45	43	46	45	43	39	46	43	40	44	29	1	Palo Verde
	Joe Neal	1	30	31	45	43	40	42	39	36	40	44	39	39	43	42	36	43	43	42	40	45	42	40	39	36	1	Joe Neal
	Green Valley	1	30	29	41	40	35	39	38	29	29	40	39	41	43	42	34	43	43	42	39	45	41	38	35	12	1	Green Valley
	Jerome Mack	1	22	24	41	38	31	35	32	26	31	36	35	36	40	40	33	41	NV	40	37	42	40	37	29	10	1	Jerome Mack
	Boulder City	1	33	32	44	42	38	41	39	46	45	45	40	44	44	43	40	44	44	41	42	45	41	39	41	38	1	Boulder City
	Jean	1	33	35	44	44	41	42	40	50	46	42	41	40	44	44	40	45	44	44	45	47	44	41	39	28	1	Jean


POC (Parameter Occurrence Code): a code used to correctly separate data from multiple instruments at one site.
NV - There are not enough valid eight-hour averages for this day (there must be eighteen valid eight-hour averages).
^N - Data from this instrument does not meet EPA quality assurance criteria and cannot be used for regulatory purposes.

Interpreting the AQI

Air Quality Index

Each NAAQS pollutant has a separate AQI scale, with an AQI rating of 100 corresponding to the concentration of the Federal Standard for that pollutant. Additional information about the AQI and how it can be used is available from the EPA's AirNow web site.

Place your mouse pointer over the scale displayed above to view information about the Air Quality Index, and each of the rating levels.

The actual index calculation is different for each parameter measured and is specified by the EPA. The following table shows the various breakpoints used in calculating the AQI.

AQI Breakpoint Definitions
AQI Range	1hr Ozone in ppm	8hr Ozone in ppm
0 - 50	Not Defined	0 - 0.054
51 - 100	Not Defined	0.055 - 0.070
101 - 150	0.125 - 0.164	0.071 - 0.085
151 - 200	0.165 - 0.204	0.086 - 0.105
201 - 300	0.205 - 0.404	0.106 - 0.200
301 - 400	0.405 - 0.504	0.201 - 0.2011
401 - 500	0.505 - 0.604	Not Defined
500+	Not Defined	Not Defined

The AQI for ozone is based on either the peak eight-hour running average since midnight OR the peak one-hour measurement since midnight. When calculating air quality for the current day, the Clark County DAQ uses a surrogate 8-hour average based on the current hourly average.

PLEASE NOTE: This data has not been verified by the Clark County Department of Air Quality and may change. This is the most current data, but it is not official until it has been certified by our technical staff. Data is collected from Clark County Department of Air Quality ambient monitoring sites and may include data collected by other outside agencies. This data is updated hourly. All times shown are in local standard time unless otherwise indicated.