Law Summary
Pollutants Covered and Limits
- For spark-ignition (gasoline-fueled) vehicles:
- Carbon Monoxide (CO): Maximum 3.5% volume, measured by idling test using NDIR Analyzer.
- Hydrocarbon (HC): Maximum 500 ppm, measured by idling test using NDIR Analyzer.
- For compression-ignition (diesel-fueled) vehicles:
- Smoke opacity: Maximum 50% HSU or 40% Bosch Smoke Meter units.
- Measured by free acceleration test from low idle engine speed using Hartridge or Bosch smoke meter.
Enforcement and Effectivity
- The standards and test procedures shall be strictly observed.
- This Memorandum Circular took effect on 01 September 1994.
- Issued for guidance and strict compliance to ensure environmental protection.
Free Acceleration Test (Diesel Vehicles)
- Scope: Measures smoke opacity for in-use diesel vehicles using free acceleration from low idle.
- Test Conditions:
- Stationary vehicle at normal engine operating temperature.
- No excessive idling prior to test to avoid cooling or fouling the combustion chamber.
- Exhaust system must be intact with no leaks or orifices that could dilute emissions.
- Equipment:
- Use opacimeter conforming to ECE Regulation No. 24 standards.
- Procedures:
- Follow manufacturer instructions for device calibration and operation.
- Vehicle in neutral gear with handbrake engaged.
- Engine warmed to normal temperature.
- Sample probe inserted deeply into tailpipe.
- Engine accelerated quickly to max delivery and smoke recorded.
- Repeat until stable readings are obtained; final result is average of three stable readings.
- For multiple exhausts, highest reading used.
- After passing test, seal injection pump full load screw to prevent tampering.
Smoke Opacity Measurement Accuracy
- Values are stable if three consecutive readings are within 0.3 m-1 and do not decrease.
- Results must be converted to DENR-approved scales if alternate smoke meters used.
Emission Test Procedure for Spark-Ignition (Gasoline) Vehicles
- Scope: Determines concentration of CO and HC emissions at idle speed.
- Equipment:
- NDIR analyzers for CO and HC gases.
- Tachometer to measure engine RPM.
- Vehicle Preparation:
- Transmission in neutral, handbrake engaged.
- Idle speed adjusted per manufacturer recommendation.
- Accessories like air conditioner turned off.
- Engine temperature at least 70°C; if not, run the vehicle before testing.
- Tailpipe checked for leaks and probe insertion ensured; correction factor applied if needed.
- Measurement:
- Calibrate instrument to zero.
- Accelerate engine to ~2,500 rpm briefly, then return to idle.
- Insert sampling probe deep in exhaust pipe, wait 20 seconds, then record CO and HC.
- For multiple exhaust outlets, average readings.
Instrument Calibration and Maintenance
- Follow manufacturer instructions for analyzer use and maintenance.
- ‘‘Span and zero’’ calibration must be performed within 4 hours before first use and after relocation.
- Calibration must be conducted away from running engines’ exhaust.
- For non-compensated analyzers, use calibration gas.
- Sample handling systems must be leakproof, clean, and free from contaminants.
- Filters and condensate traps must be checked and maintained.
Important Legal Concepts
- The standards represent interim regulatory measures for environmental protection concerning motor vehicle emissions.
- Compliance with both emission limits and prescribed test procedures is mandatory before vehicle registration.
- The Memorandum Circular’s adoption ensures uniformity and promotes public health through pollution control.
- Sealing adjustment screws post-testing emphasizes prevention of tampering and ensures continuing compliance.
- Incorporation by reference of international standards (ECE Regulations, ISO standards) for equipment and procedures ensures technical reliability and acceptance.
This detailed framework guides regulators and vehicle owners on emissions control for used imported vehicles, harmonizing environmental standards with practical testing methodologies.