Diesel exhaust fluid

Diesel exhaust fluid (DEF) means a liquid reducing agent (other than the engine fuel) used in conjunction with selective catalytic reduction to reduce NOX emissions. Diesel exhaust fluid is generally understood to be an aqueous solution of urea conforming to the specifications of ISO 22241.


40 CFR § 86.1803-01

Scoping language

The following definitions apply to this subpart:

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