Bad Air Days in Richland County, South Carolina: 1 a Year

1 bad air day a year

Fewer bad air days than most monitored US counties. Ranked 592 of 996 monitored counties, where 1 is worst.

What makes them bad: a mix of particles and ozone (47% particle days).

The bad-air season here

Most bad days here fall in June and July and November and March and May. Averaged over 2016 to 2025.

Is a purifier worth it here?

Bad air days are rare here. A standard furnace filter is enough; no purifier needed for outdoor air.
On the odd bad day, check AirNow and keep windows shut.

Better or worse than it was

In 2000 to 2009 this county averaged 31 bad days a year; in 2016 to 2025, 1. The air has improved. The worst recent year was 2016, with 5 bad days on 366 monitored days.

Date	AQI	Main pollutant
2016-11-15	174	PM2.5
2016-11-16	153	PM2.5
2024-03-14	141	PM2.5
2023-03-01	123	PM2.5
2020-06-27	117	PM2.5

The air on a normal day

Across 3,653 monitored days from 2016 to 2025, the air in Richland County rated Good on 66% of them, less often than the 72% typical of monitored counties, and Moderate on 33%. The median day sat at AQI 44; one day in ten went above 59.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)59%2,146 days
ozone40%1,474 days
nitrogen dioxide1%30 days

Year by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	212	153	0	0	47	89
2024	366	210	155	1	0	47	141
2023	365	207	154	4	0	47	123
2022	365	265	100	0	0	43	93
2021	365	268	96	1	0	42	101
2020	366	289	76	1	0	40	117
2019	365	245	120	0	0	42	93
2018	365	266	98	1	0	41	101
2017	365	247	116	2	0	44	113
2016	366	206	155	5	2	48	174
2015	365	221	144	0	0	46	90
2014	365	149	216	0	0	52	93
2013	365	204	161	0	0	47	97
2012	366	177	186	3	0	51	119
2011	365	127	217	21	0	55	150
2010	365	139	220	6	0	54	136

*2025 may be a partial year in EPA's file.

South Carolina compared

How this is counted

A bad air day is a day the county's daily AQI from EPA AirData went above 100, the level where EPA tells children, older adults and people with asthma or heart disease to cut back outdoors. Monitors do not run every day, so yearly counts are scaled to 365 days. This is the record, not today's air: for that, check AirNow. More on the method in how the county numbers are made, on the AQI 100 line in what counts as a bad air day, and on why a purifier does not touch ozone in smoke vs ozone.