| Number | Concept | Description |
|---|---|---|
| 1 | Data description | According to the definition this is the number of days when the highest daily 8-hour mean of O3/m3 exceeds 120 microgram. The highest 8-hour average for the ozone concentration on one day is determined on the basis of the progressive averages for periods of eight hours, with these periods being calculated using hourly values and updated every hour. Each average for eight hours calculated in this way applies for the day on which the period of eight hours ends, i. e. the first calculation period for a given day starts at 17.00 o'clock on the previous day and ends at 01.00 o'clock on that day, and the last calculation period is from 16.00 o'clock to 24.00 o'clock. The number of days when the mean (24-h average, i.e. daily) value for PM10 exceeds 50 microgram/m3 is being counted. |
| 2 | Coverage | Data relate to the eight cities. Ozone concentration is not being measured in the cities of Pleven and Vidin. |
| 3 | Unit of measure | Number |
| 4 | Reference period | Year |
| 5 | Time coverage | 2005 - 2009 |
| 6 | Release policy | The date of the statistical information release is shown in the Calendar of the NSI statistical surveys. |
| 7 | Dissemination format | • www.nsi.bg |
| 8 | Methodological documents | • Compilation of variable definitions - Eurostat |
| 9 | Source data | Data are collected by the Executive Environment Agency. |
| 10 | Frequency of data collection | Yearly |
| 11 | Data collection method | Measurements are done by stationary stations that are working without a break. |
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