Charleston, SC Air Quality in 2021
In 2021, Charleston's air quality (Charleston-North Charleston, SC area) had a median daily AQI of 49 (Good) across 365 monitored days. 0 days (0.0%) reached Unhealthy for Sensitive Groups or worse, 196 were Good, and the year's peak AQI was 93 (Moderate). Fine particulate matter (PM2.5) set the daily AQI on 308 of those days. The cleanest month of 2021 was February (median AQI 42, 0 days above 100) and the worst was December (median 53, 0 days above 100, peak 80).
- Good: 53.7%
- Moderate: 46.3%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
Reduce Indoor Ozone in Charleston
Today's main pollutant in Charleston is ground-level ozone (AQI 31). Important: standard HEPA filters do NOT remove ozone — only a purifier with a substantial activated-carbon bed adsorbs it. The biggest wins are cutting indoor sources (gas appliances, certain "ionizer" purifiers) and ventilating when outdoor ozone is low (early morning). A high-carbon unit helps with the gases and VOCs that linger indoors.
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How was Charleston's air quality in 2021?
Good on a typical day: median AQI 49, with 0 days above AQI 100 out of 365 monitored — the 4th cleanest of 7 years on record for the area.
- ✓Peak AQI in 2021: 93 (Moderate).
- ✓Fine particulate matter (PM2.5) was the main pollutant on 308 days.
- ✓Cleanest month: February; worst: December.
Frequently asked questions
What was the average AQI in Charleston in 2021?▾
EPA's Air Quality System puts Charleston's (Charleston-North Charleston, SC) median daily AQI for 2021 at 49, which is Good. 0 days were Unhealthy for Sensitive Groups or worse and the year's highest AQI was 93.
Which month had the worst air quality in Charleston in 2021?▾
The cleanest month of 2021 was February (median AQI 42, 0 days above 100) and the worst was December (median 53, 0 days above 100, peak 80).
Was 2021 a good or bad year for Charleston's air?▾
Among the 7 years EPA has published for the area (2019–2025), 2021 ranks 4th cleanest by days above AQI 100. 2021's median of 49 is in line with the area's typical annual median of 47.
Charleston month by month in 2021
Charleston air quality month by month, 2021 (Charleston-North Charleston, SC, EPA AQS daily AQI)
| Month | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| January | 31 | 46 | 0 | 69 | PM2.5 |
| Februarycleanest | 28 | 42 | 0 | 71 | PM2.5 |
| March | 31 | 52 | 0 | 68 | PM2.5 |
| April | 30 | 52 | 0 | 93 | PM2.5 |
| May | 31 | 49 | 0 | 62 | PM2.5 |
| June | 30 | 42 | 0 | 64 | PM2.5 |
| July | 31 | 44 | 0 | 77 | PM2.5 |
| August | 31 | 47 | 0 | 69 | PM2.5 |
| September | 30 | 49 | 0 | 74 | PM2.5 |
| October | 31 | 45 | 0 | 64 | PM2.5 |
| November | 30 | 48 | 0 | 63 | PM2.5 |
| Decemberworst | 31 | 53 | 0 | 80 | PM2.5 |
How 2021 compares
Among the 7 years EPA has published for the area (2019–2025), 2021 ranks 4th cleanest by days above AQI 100.
2021's median of 49 is in line with the area's typical annual median of 47.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Charleston
The latest EPA AirNow observation puts Charleston's AQI at 31 (O3). The figures above are multi-year annual statistics, not today's reading.
View current Charleston air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Charleston-North Charleston, SC), 2019–2025. Daily AQI per CBSA is the highest AQI reported by any monitor in the area that day; the defining parameter is the pollutant that set it. Month and season statistics pool every such day in the period across all years listed. Retrieved 2026-09-09.