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Urea and Water Help Keep Emergency Vehicle Exhaust Clean

To meet stringent new Environmental Protection Agency (EPA) emission requirements for 2010, most engine manufacturers were required to employ some new technology. Most selected after treatment which includes the use of diesel exhaust fluid (DEF) which is a solution that is comprised of urea and demineralized water.

DEF is new to the United States this year and truck drivers, including firefighter chauffeurs and operators are being required to learn about it as more and more brand new apparatus enters the national fleet.

Urea is a nitrogen compound which transforms into ammonia when heated. In DEF it is mixed at a concentration of 32.5 percent Urea to 67.5 percent water. The compound occurs naturally or is synthesized from natural gas. It's often used as a "scrubber" agent to reduce pollution from smoke-stack industries and can be used as a fertilizing agent. It's also part of urine, although not at levels sufficient for use as a catalyst.

When mixed with the purified water urea creates a nontoxic, colorless and odorless reductant agent that converts mono-nitrogen oxides (NOx) into nitrogen and water, both naturally occurring in the atmosphere. NOx, however is a significant component of air pollution, causing lung damage.

The American Trucking Associations' (ATA) Technology & Maintenance Council reports that one gallon of DEF will treat 330 gallons of diesel fuel and it has a shelf life of about 18 months. Each container will be date stamped to make sure it will meet standards.

As more trucks equipped with new emissions after treatment systems hit the road, availability of DEF has been increasing. It's now available in sizes ranging from 2.5-gallon jugs to 275-gallon totes with some fuel dealers now also selling it in bulk. Cost varies from $5 to $10 per gallon depending on the region and quantity purchased.

The North American SCR Stakeholders Group, an ad-hoc industry alliance made up of engine, truck and commercial vehicle industry representatives, as well as DEF distributors and suppliers, said SCR systems allow the engines to be tuned to deliver three to five percent fuel savings while keeping the environment clean. They can be found at

"Nitrogen oxides (NOx) contribute to smog, and smog contributes to more than 400,000 hospital visits each year for conditions related to asthma and respiratory and heart diseases - all of which have been linked to diesel exhaust," the SCR stakeholders group said. "Commitment to reducing total emissions from our engines today to the lowest possible levels is our responsibility as executives, as parents and as human beings."