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e-CFR data is current as of November 24, 2020

Title 40Chapter ISubchapter CPart 90Subpart D → §90.329


Title 40: Protection of Environment
PART 90—CONTROL OF EMISSIONS FROM NONROAD SPARK-IGNITION ENGINES AT OR BELOW 19 KILOWATTS
Subpart D—Emission Test Equipment Provisions


§90.329   Catalyst thermal stress test.

(a) Oven characteristics. The oven used for thermally stressing the test catalyst must be capable of maintaining a temperature of 500 ±5 °C and 1000 ±10 °C.

(b) Evaluation gas composition. (1) A synthetic exhaust gas mixture is used for evaluating the effect of thermal stress on catalyst conversion efficiency.

(2) The synthetic exhaust gas mixture must have the following composition:

Constituent Volume percentParts per million
Carbon Monoxide1
Oxygen1.3
Carbon Dioxide3.8
Water Vapor10
Sulfer dioxide20
Oxides of nitrogen280
Hydrogen3500
Hydrocarbon*4000
Nitrogen = Balance

*Propylene/propane ratio = 2/1.

(c) Phase 2 engines. The catalyst thermal stress test is not required for engine families certified to the Phase 2 standards.

[60 FR 34598, July 3, 1995, as amended at 64 FR 15243, Mar. 30, 1999]

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