The Federal Emergency Management Agency is setting strict new limits on formaldehyde levels in the mobile homes it buys for disaster victims.

After insisting earlier that existing trailers are safe, the agency said Friday it will take "extraordinary precautions" by buying trailers with formaldehyde emissions comparable to that of a conventional house. The requirement will cover a three-year contract to purchase up to 3,300 units. Some units will be available for this year's hurricane season.

FEMA has been criticized over high levels of formaldehyde in mobile homes given to victims of the 2005 Gulf Coast hurricanes. About 34,000 of the mobile homes remain occupied, but FEMA recently stepped up efforts to move residents out.