Nitrogen Dioxide monitoring

Carmarthenshire County Council uses diffusion tubes to carry out non- automatic (passive) monitoring of NO₂.

Passive diffusion tube samplers collect nitrogen dioxide by molecular diffusion along an inert tube to an efficient chemical absorbent. After exposure for a month, the absorbent material is chemically analysed and the concentration calculated.

The results show the annual mean in units of microgrammes per cubic metre µg/m³. A concentration of 1 µg/m³ means that one cubic metre of air contains one microgramme (millionth of a gramme) of pollutant.

The annual air quality objective for Nitrogen Dioxide is 40μg/m³.

The LAQM process places an obligation on all local authorities to regularly review and assess air quality in their areas and to determine whether or not the air quality objectives are being achieved. Where exceedances occur, or are likely to occur, the local authority must then declare an Air Quality Management Area (AQMA) and prepare an Air Quality Action Plan (AQAP) setting out the measures it intends to put in place in pursuit of the objectives.