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Government Of Assam Environment & Forest

National Ambient Air Quality Standards

  • Pollutants


    Time Weighted
    Average

    Concentration in Ambient Air
    Industrial AreaResidential, Rural & other AreasSensitive Area
    12345
    Sulphur Dioxide(SO2)
    Annual Average*80 µg/m360 µg/m315 µg/m3
    24 hours****120 µg/m380 µg/m330 µg/m3
    Oxides of Nitrogen as NO2
    Annual Average*80 µg/m360 µg/m315 µg/m3
    24 hours****120 µg/m380 µg/m330 µg/m3
    Suspended Particulate Matter (SPM)
    Annual Average*360 µg/m3140 µg/m370 µg/m3
    24 hours****500 µg/m3200 µg/m3100 µg/m3
    Respirable Particulate Matter (RPM) (size less than 10 microns)
    Annual Average*120 µg/m360 µg/m350 µg/m3
    24 hours****150 µg/m3100 µg/m375 µg/m3
    Lead
    Annual Average*1.0 µg/m30.75 µg/m30.50 µg/m3
    24 hours****1.5 µg/m31.0 µg/m30.75 µg/m3
    Ammonia1Annual Average*0.1 mg/m30.1 mg/m30.1 mg/m3
     24 hours****0.4 mg/m30.4 mg/m30.4mg/m3
    Carbon Monoxides
    8 hours**5.0 mg/m32.0 mg/m31.0 mg/m3
    1 hours10.0 mg/m34.0 mg/m32.0 mg/m3
    *Annual Arithmetic mean of minimum 104 measurements in a year taken twice a week 24 hourly at uniform interval.
    **24 hourly/ 8 hourly values should be met 98% of the time in a year. However, 2% of the time, it may exceed but not on two consecutive days.Annual Arithmetic mean of minimum 104 measurements in a year taken twice a week at uniform interval.
    NOTE:

    1. National Ambient Air Quality Standard: The levels of air quality with an adequate margin of safety, to protect the public health, vegetation and property.

    2. Whenever and wherever two consecutive values exceeds the limit specified above for the respective category, it would be considered adequate reason to institute regular/ continuous monitoring and further investigation. S.O. 384(E), Air (Prevention & Control of Pollution) Act, 1981, dated April 11, 1994] [EPA Notification: GSR 176(E), April 02, 1996].

    1. Include vide Notification SO.955(E), Air (Prevention & Control of Pollution) Act, 1981, dated October 14, 1998]