NEW ORLEANS (AP) — This holiday season, hundreds of Gulf Coast hurricane victims will make room in their cramped trailers for a belated gift from the Federal Emergency Management Agency: a tripod with an air tube and thermometer.

Starting Friday, government scientists will use those devices to measure formaldehyde emissions in hundreds of FEMA trailers. Preliminary results of the air-quality tests are due in February. A final report is expected to be released in May.

FEMA says the tests reflect its commitment to protect the safety of storm victims. Others wonder if an agency vilified for its glacial response to Hurricane Katrina hasn’t learned from mistakes it made in the aftermath of the Aug. 29, 2005, storm.

More than a year has passed since FEMA started fielding complaints from ailing trailer dwellers who suspected the trailers were emitting hazardous levels of formaldehyde, which can cause respiratory problems and has been classified as a carcinogen.

The Sierra Club started testing the air quality in FEMA trailers in April 2006. So why has it taken FEMA so much longer to respond?

Sen. Carl Levin, D-Mich., posed that question to deputy FEMA administrator Harvey Johnson during a recent Senate Homeland Security hearing in Washington, D.C.

‘‘I don’t get it, why it takes that long,’’ Levin said. ‘‘It seems to me this is totally unacceptable that it takes all this time to do a test on trailers, which were known to FEMA a year-and-a-half ago to contain unacceptable levels of formaldehyde.’’

Johnson said FEMA was ‘‘locked and loaded and ready to go’’ and could have started testing weeks ago, but needed more time to devise a system for interpreting the results.

‘‘It’s taken a long time in part because we have not had this problem before,’’ Johnson said.

‘‘This is the first time we’ve had people be in travel trailers for this length of time — up to two years — in which case some of these symptoms and the impacts on health have become more apparent.’’

In March 2006, FEMA started issuing notices advising trailer occupants in Mississippi to ventilate their units. However, the formaldehyde problem may have come to the agency’s attention months earlier.

Jesse Fineran, a FEMA employee who supervised trailer site inspections in Hancock County, Miss., said he raised concerns about formaldehyde emissions in October 2005. Fineran claims FEMA demoted him in December 2006 for speaking out on the issue.

‘‘They had the information for a long time,’’ Fineran said. ‘‘The federal government apparently has a ’don’t want to know’ attitude.’’

A FEMA spokesman in Washington wouldn’t comment on Fineran’s allegations but said the agency has been ‘‘open and upfront’’ in responding to formaldehyde concerns.

Hundreds of trailer occupants in Mississippi and Louisiana are suing companies that manufactured the units for FEMA after hurricanes Katrina and Rita.

FEMA has ‘‘spent a ton of money — over $2 billion — on trailers that are not only unsafe but worthless,’’ said Tony Buzbee, a Galveston, Texas-based lawyer for many of those plaintiffs. ‘‘They can’t even resell them.’’

FEMA has temporarily suspended sale of its trailers and says it won’t be use them as temporary shelters for disaster victims until safety concerns are addressed.

Buzbee said his firm commissioned its own tests on about 760 occupied FEMA trailers. In all but nine of those trailers, he said, formaldehyde levels exceeded limits set by the Agency for Toxic Substances and Disease Registry, an agency of the U.S. Department of Health and Human Services.

‘‘It’s almost ridiculous that they would wait two years’’ to test trailers, Buzbee said of FEMA. ‘‘I don’t expect to learn anything new from their testing.’’

The tests originally were scheduled to start Nov. 2, but FEMA says it needed more time to prepare since there are no federal guidelines governing the air quality in trailers. Over the summer, FEMA ordered tests on unoccupied trailers in Baton Rouge but later concluded the results couldn’t be used to judge the effects of formaldehyde in occupied units.

Anthony Bruno Jr., 58, whose home in Westlake, La. was destroyed by Hurricane Rita in September 2005, has been living in a trailer for nearly two years. Bruno, who is represented by Buzbee’s firm, blames his respiratory problems on fumes in his trailer.

‘‘I don’t want to sound ungrateful at all, but I do welcome the testing,’’ he said. ‘‘I’m concerned about cancer and the long-term (health) effects down the road.’’