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        SIAM is the Apex National Body representing Indian Automobile Industry

        In-use Vehicle Norms

        Petrol/CNG/LPG Driven Vehicles



        Measured at idling:

        Vehicle Type CO (%) *HC (ppm)
        2&3 wheelers (2/4 stroke) (vehicles manufactured before 31/3/2000) 4.5 9,000
        2&3 wheelers (2 stroke) (vehicles manufactured after 31/3/2000) 3.5 6,000
        2&3 wheelers (4 stroke) (vehicles manufactured after 31/3/2000) 3.5 4,500
        Bharat Stage -II compliant four wheelers 0.5 750
        Four wheelers other than Bharat Stage -II compliant 3.0 1,500

        Four Wheelers BS IV               Low Idle                                                                                                                                         0.3                 200

                                                        High Idle   ( Lambda @ 2500 +/- 200 rpm : 1+/- 0.3 or as per manf. specification)                       0.2                 

        * For CNG & LPG vehicles the measured hydrocarbon value shall be converted using the following formula and then compared with the limits
        · For CNG Vehicles- non methane hydrocarbon, NMHC = 0.3 X HC

        · For LPG Vehicles- reactive hydrocarbon, RHC = 0.5 X HC


        Diesel Vehicles


        Free Acceleration Smoke Test

        Method of Test Maximum Smoke Density
        Light Absorption Coefficient (1/m) Hartidge Units

        Free Acceleration Test for Turbo Charged engine and Naturally aspirated engine

        Free Acceleration Test for BS IV vehicles                                            







        1. Test should be done at authorised Pollution Check Centers
        2. Test should be done every six months or as per the directions of the State Government
        3. No vehicle shall ply in the country without a valid pollution under control certificate
        4. BS IV Vehicles : Test to be done once in a year



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