Federal regulators in the US have reached a tentative deal with Carnival Corp. & plc, the world’s largest cruise shipping company, on a plan to reduce air pollution from nearly a third of its cruise ships,the Baltimore Sun reports.

“Under the agreement, to be announced today, the Miami-based company pledged to install pollution control equipment on 32 of its ships over the next three years and use it while they cruise in waters near the US coast. During that time, the Environmental Protection Agency and the Coast Guard will exempt those vessels from a pending requirement that they burn less-polluting fuel,” the report said.

Carnival Corp & pc operate a total of about 100 ships between its various brands.

A treaty approved by the International Maritime Organization requires all oceangoing vessels to start using lower-sulfur fuel in 2015 whenever they are in waters deemed to be environmentally sensitive, such as within 200 miles of Canada and the United States. The requirement is meant to reduce harmful sulfur and particulate pollution from shipping.