The next phase of U.S. regulations aimed at cleaning up airborne emissions from off-road diesel engines will start taking effect in just nine months. The rule, called Tier 4, will all but eliminate the amount of diesel particulate matter (soot) and nitrogen oxides (NOx) that new construction equipment will put into the atmosphere.
Split into two subrules, the Tier 4 standard begins phasing in with an interim rule in January 2011 for engines from 175 horsepower to 750 hp and, in 2012, for engines from 75 hp to 175 hp. The Tier 4 rule cuts down the soot an engine may emit by 90% compared to the current Tier 3 standard, and it cuts the amount of NOx an engine is allowed to put out by 45%. What will follow in 2014 is an even tougher Tier 4 Final standard, which will cut NOx output by another 45%. Then, new construction equipment will emit virtually no NOx or soot.