Air at the Bor-Gradski park station
Bor, Serbia
Network: Agency for Environmental Protection · Station code: RS0009A
This year, up to yesterday (October 7)
at least
1 day
with a daily average of particulate matter PM10 above the EU limit of 50 µg/m³.
Readings are missing for part of the period, so the real number may be higher.
In 2025: 16 days above the limit, 35 allowed.
Worst day: October 7, 2026, PM10 61 µg/m³ as a daily average, 1.2 times the limit.
Daily average for 72 of 280 days · data for 2026 not yet finally verified · Yardstick: EU limits (Directive 2008/50/EC)
Fair
Air now · Measured at 22:00
Latest values
Latest value: Wed 22:00
| Pollutant | Value | Level |
|---|---|---|
| PM10 | 42.3 µg/m³ | Fair |
| SO₂ | 10.4 µg/m³ | Good |
How the air is changing
Over the last seven days there was more PM10 in the air than the week before.
- PM10: average 33 µg/m³, week before 18.5 µg/m³
- SO₂: average 10.4 µg/m³, week before 9.8 µg/m³
Last month there was less PM10 in the air than the month before.
- PM10: average 21.6 µg/m³, month before 28.1 µg/m³
- SO₂: average 11.5 µg/m³, month before 12 µg/m³
Show
Particulate matter PM10
42.3
Nowµg/m³
Measured at 22:00
60.5
Last 24 hoursµg/m³
measured in 92 % of hours · provisional
33
Last 7 daysµg/m³
measured in 99 % of hours · provisional
25
Last 30 daysµg/m³
measured in 100 % of hours · provisional
too few readings
Last 12 months
measured in 43 % of hours · provisional
Values as a table
| Hour to | µg/m³ | Note |
|---|---|---|
| Wednesday, 10/7 | ||
| 23:00 | 22 | model estimate, not counted |
| 22:00 | 42.3 | |
| 21:00 | 52.3 | |
| 20:00 | 67.3 | |
| 19:00 | 91.9 | |
| 18:00 | 95.7 | |
| 17:00 | 38.2 | |
| 16:00 | 32.5 | |
| 15:00 | 31.5 | |
| 14:00 | 47.5 | |
| 13:00 | 56.3 | |
| 12:00 | 81.6 | |
| 11:00 | 126.4 | |
| 10:00 | 77.9 | |
| 09:00 | 75.2 | |
| 08:00 | 69.9 | |
| 07:00 | 55.3 | |
| 06:00 | 42.5 | |
| 05:00 | 41 | |
| 04:00 | 42.2 | |
| 03:00 | 54.9 | |
| 02:00 | 66.1 | |
| 01:00 | 42.7 | |
| Tuesday, 10/6 | ||
| 00:00 | 41 | |
| 23:00 | 42 | |
| 22:00 | 51.3 | |
| 21:00 | 61.6 | |
| 20:00 | 57.8 | |
| 19:00 | 44.5 | |
| 18:00 | 46.1 | |
| 17:00 | 42 | |
| 16:00 | 57.6 | |
| 15:00 | 59.6 | |
| 14:00 | 43.4 | |
| 13:00 | 44.2 | |
| 12:00 | 59.6 | |
| 11:00 | 93.4 | |
| 10:00 | 101 | |
| 09:00 | 29.5 | |
| 08:00 | 18.9 | |
| 07:00 | 9.1 | |
| 06:00 | 9 | |
| 05:00 | 8.5 | |
| 04:00 | 8.6 | |
| 03:00 | 10.1 | |
| 02:00 | 16.6 | |
| 01:00 | 16.8 | |
| Monday, 10/5 | ||
| 00:00 | 18.1 | |
| 23:00 | 29.1 | |
| 22:00 | 25.3 | |
| 21:00 | 23.7 | |
| 20:00 | 26.4 | |
| 19:00 | 30.6 | |
| 18:00 | 16.5 | |
| 17:00 | 14 | |
| 16:00 | 17.1 | |
| 15:00 | 24.4 | |
| 14:00 | 19.5 | |
| 13:00 | 39.7 | |
| 12:00 | 55 | |
| 11:00 | 82.1 | |
| 10:00 | 62.5 | |
| 09:00 | 29.8 | |
| 08:00 | 13.9 | |
| 07:00 | 10 | |
| 06:00 | 11.1 | |
| 05:00 | 11.7 | |
| 04:00 | 13 | |
| 03:00 | 12.8 | |
| 02:00 | 13.4 | |
| 01:00 | 12.6 | |
| Sunday, 10/4 | ||
| 00:00 | 12.4 | |
| 23:00 | 12.8 | |
| 22:00 | 14 | |
| 21:00 | 14.6 | |
| 20:00 | 24 | |
| 19:00 | 22 | |
| 18:00 | 19.7 | |
| 17:00 | 13.4 | |
| 16:00 | 11.4 | |
| 15:00 | 18.4 | |
| 14:00 | 13.8 | |
| 13:00 | 25.5 | |
| 12:00 | 35.3 | |
| 11:00 | 125 | |
| 10:00 | 81 | |
| 09:00 | 34.5 | |
| 08:00 | 16.2 | |
| 07:00 | 15.2 | |
| 06:00 | 14.6 | |
| 05:00 | 15.1 | |
| 04:00 | 15.8 | |
| 03:00 | 16.7 | |
| 02:00 | 16.3 | |
| 01:00 | 18.8 | |
| Saturday, 10/3 | ||
| 00:00 | 21.2 | |
| 23:00 | 28.2 | |
| 22:00 | 29 | |
| 21:00 | 29.1 | |
| 20:00 | 32.2 | |
| 19:00 | 36.1 | |
| 18:00 | 19.7 | |
| 17:00 | 24.9 | |
| 16:00 | 23.5 | |
| 15:00 | 24.2 | |
| 14:00 | 28.2 | |
| 13:00 | 24.3 | |
| 12:00 | 27.9 | |
| 11:00 | 69.9 | |
| 10:00 | 76.4 | |
| 09:00 | 23.7 | |
| 08:00 | 13.8 | |
| 07:00 | 12.7 | |
| 06:00 | 15 | |
| 05:00 | 18.4 | |
| 04:00 | 20 | |
| 03:00 | 20.6 | |
| 02:00 | 21.6 | |
| 01:00 | 24.8 | |
| Friday, 10/2 | ||
| 00:00 | 22.6 | |
| 23:00 | 25 | |
| 22:00 | 17.5 | |
| 21:00 | 24.2 | |
| 20:00 | 58.4 | |
| 19:00 | 33.2 | |
| 18:00 | 27.1 | |
| 17:00 | 23.8 | |
| 16:00 | 25.2 | |
| 15:00 | 24.5 | |
| 14:00 | 24.7 | |
| 13:00 | 18.9 | |
| 12:00 | 21.9 | |
| 11:00 | 31.3 | |
| 10:00 | 67.9 | |
| 09:00 | 30.8 | |
| 08:00 | 16.4 | |
| 07:00 | 14.4 | |
| 06:00 | 14.2 | |
| 05:00 | 13.8 | |
| 04:00 | 12.7 | |
| 03:00 | 13.6 | |
| 02:00 | 13.9 | |
| 01:00 | 15.1 | |
| Thursday, 10/1 | ||
| 00:00 | 15.9 | |
| 23:00 | 19.3 | |
| 22:00 | 20.3 | |
| 21:00 | 22.6 | |
| 20:00 | 44.5 | |
| 19:00 | 43 | |
| 18:00 | 50.3 | |
| 17:00 | 49.2 | |
| 16:00 | 44.6 | |
| 15:00 | 37.5 | |
| 14:00 | 39 | |
| 13:00 | 34.6 | |
| 12:00 | 31.2 | |
| 11:00 | 44.3 | |
| 10:00 | 59.8 | |
| 09:00 | 32.6 | |
| 08:00 | 17.6 | |
| 07:00 | 14.9 | |
| 06:00 | 13.9 | |
| 05:00 | 12.9 | |
| 04:00 | 11.6 | |
| 03:00 | 11.5 | |
| 02:00 | 15.5 | |
Values as a table
| Day | µg/m³ | Note |
|---|---|---|
| Wed, 10/7 | 60.5 | above the limit · provisional |
| Tue, 10/6 | 40.5 | provisional |
| Mon, 10/5 | 25.5 | provisional |
| Sun, 10/4 | 25.3 | provisional |
| Sat, 10/3 | 27.7 | provisional |
| Fri, 10/2 | 24.6 | provisional |
| Thu, 10/1 | 29.4 | provisional |
| Wed, 9/30 | 36.9 | provisional |
| Tue, 9/29 | 22.4 | provisional |
| Mon, 9/28 | 16.6 | provisional |
| Sun, 9/27 | 14.2 | provisional |
| Sat, 9/26 | 17.1 | provisional |
| Fri, 9/25 | 10.5 | provisional |
| Thu, 9/24 | 11.9 | provisional |
| Wed, 9/23 | 11.2 | provisional |
| Tue, 9/22 | 16.6 | provisional |
| Mon, 9/21 | 28.7 | provisional |
| Sun, 9/20 | 26 | provisional |
| Sat, 9/19 | 21.5 | provisional |
| Fri, 9/18 | 31.5 | provisional |
| Thu, 9/17 | 25.9 | provisional |
| Wed, 9/16 | 23 | provisional |
| Tue, 9/15 | 17 | provisional |
| Mon, 9/14 | 12.3 | provisional |
| Sun, 9/13 | 12.6 | provisional |
| Sat, 9/12 | 16.2 | provisional |
| Fri, 9/11 | 49.6 | provisional |
| Thu, 9/10 | 33.8 | provisional |
| Wed, 9/9 | 34.1 | provisional |
| Tue, 9/8 | 28.5 | provisional |
Values as a table
| Month | µg/m³ | a year earlier | Note |
|---|---|---|---|
| October 2026 so far | 33 | 12.7 | measured in 99 % of hours · provisional · year before: same days |
| September 2026 | 21.6 | 26.5 | measured in 100 % of hours · provisional |
| August 2026 | 28.1 | 24.8 | measured in 99 % of hours · provisional |
| July 2026 | too few readings | 22.9 | measured in 15 % of hours · provisional |
| June 2026 | too few readings | 28.1 | |
| May 2026 | too few readings | 16.4 | |
| April 2026 | too few readings | 26.6 | |
| March 2026 | too few readings | 34.7 | 15 days without data from the station |
| February 2026 | too few readings | 42.5 | 28 days without data from the station |
| January 2026 | too few readings | 29.7 | 31 days without data from the station |
| December 2025 | 19 | measured in 100 % of hours · verified | |
| November 2025 | 19 | measured in 100 % of hours · verified |
PM10 by year
Yardstick: EU limits (Directive 2008/50/EC)
| Measure | 2026* | 2025 |
|---|---|---|
| Days above 50 µg/m³ (allowed 35) | ≥ 1² | 16 |
| Annual average, µg/m³ (EU limit 40) | too few | 25.7 |
| Highest daily average, µg/m³ | 61October 7 | 75February 26 |
| Highest hourly value, µg/m³ | 242August 4 | 306June 24 |
| Hours measured | 26 % | 100 % |
| Days without any reading from the station | 74 | 0 |
* 2026 up to October 7; the average since the start of the year is not yet an annual average.
The monitoring networks have not yet finally verified this year’s data. The EEA publishes verified values once a year.
≥ means at least: more than a tenth of the days or hours are missing, so the real number may be higher.
² Too few readings to compare with the number allowed: the figure covers only what was measured.
Unverified hourly values of particulate matter from 975 µg/m³ up, and single spikes from 500 µg/m³ up between low values, count as missing. In the verified data for BiH from 2023 to 2025 no hour was above 600 µg/m³.
■ and a figure in red: more than is allowed for the whole year.
Sulphur dioxide SO₂
10.4
Nowµg/m³
Measured at 22:00
13.6
Last 24 hoursµg/m³
measured in 92 % of hours · provisional
10.4
Last 7 daysµg/m³
measured in 98 % of hours · provisional
11.3
Last 30 daysµg/m³
measured in 98 % of hours · provisional
too few readings
Last 12 months
measured in 78 % of hours · 2 months with too few readings · provisional
Days in 2023: SO₂, daily average above 125 µg/m³
No measured day above the limit.
- above the limit
- below the limit
Months of 2023
| Month | Days above 125 | Hours above 350 | Highest day | No readings |
|---|---|---|---|---|
| January | 0 | 0 | 33 | 0 |
| February | 0 | 0 | 33 | 0 |
| March | 0 | 0 | 32 | 0 |
| April | 0 | 3 | 106 | 0 |
| May | 0 | 0 | 61 | 0 |
| June | 0 | 1 | 64 | 0 |
| July | 0 | 0 | 19 | 0 |
| August | 0 | 0 | 33 | 0 |
| September | 0 | 0 | 74 | 0 |
| October | 0 | 0 | 29 | 0 |
| November | 0 | 1 | 36 | 0 |
| December | 0 | 0 | 28 | 0 |
Values in µg/m³. ■ marks a month with at least one day above the limit; the number allowed applies to the whole year. “No readings”: days on which not a single reading came from the station.
Values as a table
| Hour to | µg/m³ | Note |
|---|---|---|
| Wednesday, 10/7 | ||
| 22:00 | 10.4 | |
| 21:00 | 14.7 | |
| 20:00 | 14.3 | |
| 19:00 | 14.2 | |
| 18:00 | 14.5 | |
| 17:00 | 10.7 | |
| 16:00 | 11 | |
| 15:00 | 11.5 | |
| 14:00 | 10.5 | |
| 13:00 | 11.1 | |
| 12:00 | 14 | |
| 11:00 | 69.3 | |
| 10:00 | 9.6 | |
| 09:00 | 9.1 | |
| 08:00 | 9 | |
| 07:00 | 9.1 | |
| 06:00 | 9 | |
| 05:00 | 9.1 | |
| 04:00 | 9.4 | |
| 03:00 | 9.5 | |
| 02:00 | 9.6 | |
| 01:00 | 9.5 | |
| Tuesday, 10/6 | ||
| 00:00 | 9.6 | |
| 23:00 | 9.4 | |
| 22:00 | 10.2 | |
| 21:00 | 10.9 | |
| 19:00 | 28.1 | |
| 18:00 | 23.1 | |
| 17:00 | 14.1 | |
| 16:00 | 14 | |
| 15:00 | 12.9 | |
| 14:00 | 10.3 | |
| 13:00 | 12 | |
| 12:00 | 11.7 | |
| 11:00 | 15 | |
| 10:00 | 15.2 | |
| 09:00 | 8.9 | |
| 08:00 | 8.7 | |
| 07:00 | 8.9 | |
| 06:00 | 8.9 | |
| 05:00 | 8.9 | |
| 04:00 | 9 | |
| 03:00 | 9 | |
| 02:00 | 9.1 | |
| 01:00 | 9.5 | |
| Monday, 10/5 | ||
| 00:00 | 10.8 | |
| 23:00 | 16.1 | |
| 22:00 | 24.3 | |
| 21:00 | 26.3 | |
| 20:00 | 14.9 | |
| 19:00 | 10 | |
| 18:00 | 9.2 | |
| 17:00 | 9.2 | |
| 16:00 | 9.5 | |
| 15:00 | 10.7 | |
| 14:00 | 9.4 | |
| 13:00 | 9.5 | |
| 12:00 | 10.1 | |
| 11:00 | 10.8 | |
| 10:00 | 9.5 | |
| 09:00 | 8.7 | |
| 08:00 | 8.6 | |
| 07:00 | 8.5 | |
| 06:00 | 8.5 | |
| 05:00 | 8.6 | |
| 04:00 | 8.6 | |
| 03:00 | 8.4 | |
| 02:00 | 8.6 | |
| 01:00 | 8.7 | |
| Sunday, 10/4 | ||
| 00:00 | 8.6 | |
| 23:00 | 8.6 | |
| 22:00 | 8.7 | |
| 21:00 | 8.5 | |
| 20:00 | 8.6 | |
| 19:00 | 9 | |
| 18:00 | 9 | |
| 17:00 | 9.1 | |
| 16:00 | 9.1 | |
| 15:00 | 9.6 | |
| 14:00 | 8.8 | |
| 13:00 | 9 | |
| 12:00 | 9.9 | |
| 11:00 | 14.9 | |
| 10:00 | 9.3 | |
| 09:00 | 8.3 | |
| 08:00 | 8.4 | |
| 07:00 | 8.3 | |
| 06:00 | 8.1 | |
| 05:00 | 8.4 | |
| 04:00 | 8.3 | |
| 03:00 | 8.4 | |
| 02:00 | 8.2 | |
| 01:00 | 8.3 | |
| Saturday, 10/3 | ||
| 00:00 | 8.5 | |
| 23:00 | 8.5 | |
| 22:00 | 8.4 | |
| 21:00 | 8.5 | |
| 20:00 | 10.2 | |
| 18:00 | 9.2 | |
| 17:00 | 8.9 | |
| 16:00 | 8.9 | |
| 15:00 | 8.9 | |
| 14:00 | 8.6 | |
| 13:00 | 9 | |
| 12:00 | 9 | |
| 11:00 | 9.9 | |
| 10:00 | 9 | |
| 09:00 | 8.4 | |
| 08:00 | 8.2 | |
| 07:00 | 8.1 | |
| 06:00 | 8.1 | |
| 05:00 | 8.1 | |
| 04:00 | 8.1 | |
| 03:00 | 8.4 | |
| 02:00 | 8.4 | |
| 01:00 | 8.6 | |
| Friday, 10/2 | ||
| 00:00 | 8.5 | |
| 23:00 | 8.3 | |
| 22:00 | 8.3 | |
| 21:00 | 8.7 | |
| 20:00 | 10.4 | |
| 19:00 | 13.7 | |
| 18:00 | 11.7 | |
| 17:00 | 10.7 | |
| 16:00 | 9.2 | |
| 15:00 | 9.3 | |
| 14:00 | 9.4 | |
| 13:00 | 8.7 | |
| 12:00 | 9 | |
| 11:00 | 9.5 | |
| 10:00 | 9.5 | |
| 09:00 | 8.4 | |
| 08:00 | 8.4 | |
| 07:00 | 8.4 | |
| 06:00 | 8.1 | |
| 05:00 | 8.1 | |
| 04:00 | 8.1 | |
| 03:00 | 8.4 | |
| 02:00 | 8.4 | |
| 01:00 | 8.4 | |
| Thursday, 10/1 | ||
| 00:00 | 8.4 | |
| 23:00 | 8.4 | |
| 22:00 | 8.4 | |
| 21:00 | 8.7 | |
| 20:00 | 9.2 | |
| 19:00 | 11.3 | |
| 18:00 | 13.5 | |
| 17:00 | 11.5 | |
| 16:00 | 10.7 | |
| 15:00 | 9.6 | |
| 14:00 | 9 | |
| 13:00 | 8.9 | |
| 12:00 | 9.3 | |
| 11:00 | 10.1 | |
| 10:00 | 10.7 | |
| 09:00 | 8.7 | |
| 08:00 | 8.5 | |
| 07:00 | 8.4 | |
| 06:00 | 8.3 | |
| 05:00 | 8.6 | |
| 04:00 | 8.6 | |
| 03:00 | 8.5 | |
| 02:00 | 8.3 | |
Values as a table
| Day | µg/m³ | Note |
|---|---|---|
| Wed, 10/7 | 13.6 | provisional |
| Tue, 10/6 | 12.1 | provisional |
| Mon, 10/5 | 11.1 | provisional |
| Sun, 10/4 | 9 | provisional |
| Sat, 10/3 | 8.7 | provisional |
| Fri, 10/2 | 9.2 | provisional |
| Thu, 10/1 | 9.3 | provisional |
| Wed, 9/30 | 10.1 | provisional |
| Tue, 9/29 | 9.1 | provisional |
| Mon, 9/28 | 9.5 | provisional |
| Sun, 9/27 | 9.8 | provisional |
| Sat, 9/26 | 9.9 | provisional |
| Fri, 9/25 | 9.3 | provisional |
| Thu, 9/24 | 10.7 | provisional |
| Wed, 9/23 | 10 | provisional |
| Tue, 9/22 | 9.8 | provisional |
| Mon, 9/21 | 10.7 | provisional |
| Sun, 9/20 | 14 | provisional |
| Sat, 9/19 | 9.6 | provisional |
| Fri, 9/18 | 19.3 | provisional |
| Thu, 9/17 | 15 | provisional |
| Wed, 9/16 | 14.6 | provisional |
| Tue, 9/15 | 11.6 | provisional |
| Mon, 9/14 | 14 | provisional |
| Sun, 9/13 | 8.8 | provisional |
| Sat, 9/12 | 9 | provisional |
| Fri, 9/11 | 15.4 | provisional |
| Thu, 9/10 | 13.9 | provisional |
| Wed, 9/9 | 11.5 | provisional |
| Tue, 9/8 | 11.8 | provisional |
Values as a table
| Month | µg/m³ | a year earlier | Note |
|---|---|---|---|
| October 2026 so far | 10.4 | 6.6 | measured in 98 % of hours · provisional · year before: same days |
| September 2026 | 11.5 | 11.6 | measured in 99 % of hours · provisional |
| August 2026 | 12 | 12.1 | measured in 98 % of hours · provisional |
| July 2026 | 10.6 | 11.2 | measured in 99 % of hours · provisional |
| June 2026 | 9.5 | 10.3 | measured in 98 % of hours · provisional |
| May 2026 | 7.8 | 10.1 | measured in 99 % of hours · provisional |
| April 2026 | 8.9 | 11 | measured in 98 % of hours · provisional |
| March 2026 | too few readings | 14.3 | measured in 51 % of hours · provisional · 15 days without data from the station |
| February 2026 | too few readings | 15.7 | 28 days without data from the station |
| January 2026 | too few readings | 13.1 | 31 days without data from the station |
| December 2025 | 9.8 | 12.4 | measured in 99 % of hours · verified |
| November 2025 | 10.8 | 13.3 | measured in 98 % of hours · verified |
SO₂ by year
Yardstick: EU limits (Directive 2008/50/EC)
| Measure | 2026* | 2025 | 2024 |
|---|---|---|---|
| Days above 125 µg/m³ (allowed 3) | 0² | 0 | 0 |
| Hours above 350 µg/m³ (allowed 24) | 0² | 0 | 1 |
| Hours above 500 µg/m³, three hours in a row (alert threshold) | 0 | 0 | 0 |
| Annual average, µg/m³ | too few | 11.4 | 13.9 |
| Highest daily average, µg/m³ | 27March 19 | 46November 25 | 48May 16 |
| Highest hourly value, µg/m³ | 332July 22 | 327March 13 | 365December 19 |
| Hours measured | 72 % | 98 % | 98 % |
| Days without any reading from the station | 74 | 0 | 0 |
* 2026 up to October 7; the average since the start of the year is not yet an annual average.
The monitoring networks have not yet finally verified this year’s data. The EEA publishes verified values once a year.
² Too few readings to compare with the number allowed: the figure covers only what was measured.
■ and a figure in red: more than is allowed for the whole year.
There is no allowed number for the warning and alert thresholds: every such hour or day is in red.
The column for 2023 is shown on wider screens.
Compared with the new EU rules and the WHO recommendation
This is not the yardstick for the verdict above, only a comparison. From 2030 the EU tightens its limits (Directive (EU) 2024/2881), and since 2021 the World Health Organization has recommended even lower values.
- EU from 2030: daily 50 µg/m³, 18 days allowed. In 2023 there were 7 such days.
- WHO 2021: daily 40 µg/m³, at most three to four days a year. In 2023 there were 18 such days.
- EU from 2030: annual average 20 µg/m³. Average in 2023: 16 µg/m³.
Sources: Directive (EU) 2024/2881, Annex I; WHO global air quality guidelines 2021, table 0.1. Checked against the texts on 7 October 2026.
Outages in the last 12 months
Every period of at least 24 hours in which no reading arrived from this station.
Days without a reading: 74
1 outage, 1,776 hours in total in the last 12 months.
Timeline of outages from October 8, 2025 to today
| From | To | Duration |
|---|---|---|
| Jan 1, 2026 00:00 | Mar 16, 2026 00:00 | 74 days |
Calculated from the hourly values the EEA publishes. If late values arrive afterwards, an outage gets shorter or disappears.
Where the data comes from
Measured by Agency for Environmental Protection. We take the values from the European Environment Agency (EEA) under the CC BY 4.0 licence.
Values marked provisional have not been fully checked by the network yet. The EEA publishes verified data for the previous year once a year, usually by the end of September.
An hourly value is the average of one hour. We show the end of the hour: the value to 18:00 was measured from 17:00 to 18:00.
A day runs from midnight to midnight local time.
We only show an average when at least three out of four hours in the period have a reading. The EU air quality directive requires this for daily averages, and we apply the same rule to longer periods. We compare an annual average with the EU limit only once 90 % of hours are measured, as the directive requires. For 12 months and for a year we ask for more: if less than 90 % of hours are measured, every full calendar month needs readings for at least half of its hours. Otherwise a whole season could be missing from the average, such as summer, when ozone is highest.
We do not call a difference of up to 10 % a change, nor one of up to 1 µg/m³ at low levels, because weather and measurement uncertainty alone cause differences that size.
When a station sends no reading, the EEA sometimes fills the hour with a model estimate. We draw those hours dashed and leave them out of every average.
The EU limits come from Directive 2008/50/EC. Here they serve as a yardstick for comparison. When more than a tenth of the days or hours are missing, the number of exceedances can only be higher, so we write “at least” in front of it.
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