NEW ORLEANS — Occupants of FEMA trailers placed in disaster areas may now get their units tested for formaldehyde contamination if they file a request.

The Federal Emergency Management Agency says that for the first time it will open up the testing program to hurricane evacuees living in thousands of federally supplied trailers and mobile homes along the Gulf Coast, and to anyone using similar FEMA-supplied trailers in other states that have been affected by floods, tornadoes and other disasters.

The Centers for Disease Control and Prevention said this month that tests on a sample of 519 trailers and mobile homes in Louisiana and Mississippi detected formaldehyde at levels that averaged about five times what people are exposed to in most modern homes.

Formaldehyde is a preservative also commonly used in construction materials; it can lead to breathing problems and is also believed to cause cancer. Critics had argued that FEMA should have reacted sooner to concerns that formaldehyde is to blame for ailments reported by trailer occupants.

In a news release issued Friday, FEMA said testing could begin as early as this week and would begin with residents of the Gulf Coast who have already requested tests.

About 200 trailers and mobile homes would be tested each week, FEMA said. The contract to do the testing went to Bureau Veritas, which also did the recent testing of the 519 units, according to FEMA.

Bureau Veritas, with operations in 140 countries, specializes in quality assurance, health, safety and environmental services. The company says it helps clients “comply with standards and regulations relating to quality, health and safety, environment and social responsibility.”