Automobile emission standards do not apply to vehicles under the management of the Ministry of National Defense and the Ministry of Public Security .
According to the National Technical Regulation on exhaust gas emissions of automobiles participating in road traffic (QCVN 85:2025), a forced combustion engine is an internal combustion engine that operates on the principle of forced combustion by an external heat source; a compression combustion engine is an internal combustion engine that operates on the principle of self-ignition of fuel in an environment of high temperature and pressure; Smoke level N (%HSU) is the portion of light that is blocked and does not reach the receiver of the measuring device when transmitted from a light source through the smoke environment of the exhaust gas of a compression combustion engine and is calculated as a percentage of Hatridge smoke units.

For vehicles equipped with positive-ignition engines, the CO and HC concentrations of exhaust gas are determined according to the method specified in TCVN 6204:2008 (ISO 3929:2003) - Road vehicles - Methods for measuring exhaust gas during inspection or maintenance.
Measurement of smoke level of automobile exhaust gas with compression ignition engine is performed by measuring exhaust gas sample according to the free acceleration engine measurement cycle. The free acceleration engine measurement cycle (hereinafter referred to as the free acceleration cycle) is specified in section 9.4.2 of TCVN 7663:2007 (ISO QCVN 85:2025/BNNMT 3 11614:1999) - Reciprocating piston compression ignition internal combustion engine - Equipment for measuring smoke level and determining light absorption coefficient of exhaust gas.
The maximum allowable limit values of CO, HC and smoke N (%HSU) parameters of automobile exhaust gas are specified as follows:
Automobile emission testing must be performed by a certified unit qualified to conduct technical safety and environmental protection quality testing under the state management responsibility of the Ministry of Construction .
Automobile emission measuring equipment must meet the technical requirements specified in QCVN 103:2024/BGTVT - National technical regulation on technical facilities and locations of motor vehicle inspection facilities, motorcycle and motorbike emission inspection facilities, legal regulations on measurement and current regulations.
Source: https://baolaocai.vn/quy-dinh-moi-doi-voi-van-de-khi-thai-xe-o-to-tu-ngay-16122025-post648398.html
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