The call was like hundreds of others received by D.C. firefighters in the last few years: A woman in a downtown lobbying office had opened an envelope containing white powder and scattered the substance all over herself.

Minutes after arriving at the scene on a recent Thursday, fire officials quickly ran through a threat assessment: The woman was not showing signs of ill health. She had not reported receiving threats. Her employer was not a high-risk target. They determined that it was either a hoax or an innocent mistake.

Even so, as police officers, bystanders and federal agents looked on, two specially trained D.C. firefighters donned protective masks, boots, gloves and breathing tanks. Looking like astronauts, they waddled into the building, carrying electronic meters and test tubes to help them confirm whether the substance was harmful.

The two firefighters, who emerged 20 minutes later with proof that their assessment had been correct, are members of the Hazardous Materials Unit in the D.C. Department of Fire and Emergency Medical Services.

They are the District's first line of response to chemical, biological or nuclear attack. Fire officials say they have spent much of the last few years trying to improve the team's ability to handle such incidents. Just three years ago, in the months after the Sept. 11, 2001, attacks, a private consulting firm found that the hazmat team suffered from "a lack of funding, training, staffing, equipment and top fire management support." The consultants said the team was deficient in 10 areas that they measured.

Last August, serious questions were again raised about the team's abilities when 12 of 14 firefighters failed a proficiency exam that tested their knowledge of handling hazardous materials scenes and using and caring for their equipment, fire officials said.

Since the failures, the department has revamped the unit, sending most of the old technicians to other assignments and recruiting new firefighters to fill their slots. The department has dispatched the new hazmat team to out-of-state seminars about nuclear, biological and chemical weapons and started a cross-training program to give them more emergency skills. In all, fire officials say they have spent about $50,000 on training the new team members.

With the 2001 terrorist attacks and deadly anthrax mailings casting a not-so-distant shadow over their work, the 24-member hazmat team simply cannot afford to take chances with training or with how it responds to incidents, fire officials said.

"We want a professional response," said Battalion Chief Larry Schultz, who oversees the special operations division, which includes the hazmat unit. "What we do in the first 20 minutes will determine, to a large extent, how many people will live and how many will die."

Observers say the team has improved in the last year.

"They are better off than when they failed the test," said D.C. Council member Kathy Patterson (D-Ward 3), who chairs the council's judiciary committee. "I'm not sure there is anything more important than hazmat training in the post-September 11 world."

Before the anthrax mailings began here in October 2001, leaving five dead and sickening 17 others, the hazmat unit mostly responded to calls about fuel spills and natural gas leaks. Since then, the team has handled 2,100 incidents -- about 35 to 40 percent of which dealt with suspicious powders, odors or chemicals, officials estimated.

During those call-outs, team members enter a potentially contaminated building to determine the nature of a substance. Then they must figure out ways to contain any biological and chemical agents and decide how to treat victims.

While working to rescue people and assess the threat, firefighters must also collect the substance for law enforcement authorities, most often the FBI.

The team has jurisdiction throughout almost all of Washington, except for the Capitol and a few other federal buildings. In the anthrax attacks, the team backed up U.S. Capitol Police officers, who have their own unit.

When authorities discovered ricin, a toxin, in a Senate mailroom early this year, the D.C. hazmat team operated decontamination centers for law enforcement officials entering and leaving the building during the investigation, officials said.

Schultz and other commanders said the department has dispatched unit members to seminars and other instruction programs to learn new skills. Firefighter Jim West, for example, recently worked with sarin gas and VX nerve agents at an Alabama training center, and Lt. Robert Callahan has been sent to Nevada to better understand radiation.

The department has also pushed the team to learn how to respond to other emergencies, such as building collapses and other urban hazards.

"We need to be prepared for anything," Schultz said.

The training has often been tedious and academic, requiring firefighters to master chemistry and study textbooks on biological warfare. That has been a challenge for many who joined the department to experience the adrenaline rush of running into a raging blaze.

They said they must approach hazardous materials incidents in the opposite fashion: taking time to plan their attack and containment strategies.

"There's a lot more thinking than straight action," said firefighter Jack Spencer, who joined the unit five months ago. "It's different than working on a fire ground. It's a lot more technical."

On a recent steamy morning, firefighter Earl Tolbert practiced getting into a suit for the first time and practiced decontaminating himself after entering a building laced with chemical or biological agents. He had just been certified as a hazardous materials technician. The department has about 240 members who are certified to deal with hazardous materials. Fire officials say those 240 are backups for the hazardous materials team. Firefighters on other engines and trucks also need to understand how to deal with weapons of mass destruction because they might arrive on the scene before hazmat members, officials said.

As experienced team members coached him, Tolbert went step by step through the decontamination process. Clad in the white suit and breathing through his oxygen tank, he waddled into a special tent and was showered with water. Then he stepped into a small wading pool and was scrubbed with a special cleaning solution by his colleagues.

Finally, 10 minutes later, he was allowed to take off his mask.

"We drill so you can't miss a step," said Capt. Mike Bashore, the commander of the hazmat team. "It's very methodical, step by step. If you miss a step, someone could get contaminated."

In addition to the constant training sessions, the team also treats each call-out as a drill to hone skills needed in a real-life crisis.

In the recent response to the downtown lobbying firm, hazmat team members Callahan and Ruth Cade entered the building with their electronic meters and test tubes and took an elevator to the ninth floor. There, they entered the offices and found an envelope stuffed with what appeared to be white powder.

They ran their first battery of tests to make sure no chemicals were in the room. Then they put the substance into test tubes to make sure they were not dealing with a biological agent.

All the tests came back negative, they said.

They radioed their results to Schultz, who was waiting outside.

When Callahan and Cade emerged from the office building and removed their disposable suits, their blue T-shirts and pants were soaked with sweat.

"We don't cut corners," Callahan said.

Later, the two firefighters leaned over sophisticated testing gear to determine the identity of the substance.

The complex molecular name surprised them, forcing the firefighters to flip through chemical dictionaries and hazardous materials textbooks for information. An FBI agent finally got the answer after calling a bureau chemist: The powder was a form of ground-up plastic.

After the test, the firefighters turned the envelope and other material over to the FBI, which responds to every call for a suspicious powder in the District.

Schultz conceded that firefighters didn't need to conduct that second round of tests to determine the nature of the substance. They had already determined that the substance was not harmful. And, if prosecutors wanted to bring charges against a hoaxster, they would need to run a more sophisticated analysis at a crime laboratory.

But Schultz and the firefighters said they wanted to give the startled lobbyist peace of mind.

She had been nervous and was having trouble breathing, a normal reaction of people worried that they might have been exposed to a toxic substance, Schultz said.

To the woman and others in her situation, Schultz said, the scare was not a dry-run or a drill.

To her, it was all too real.

Hazmat technician Ruth Cade prepares to enter a building on 18th Street NW to investigate a call about a white powder found in an envelope. Tests ultimately showed that the powder was harmless. Firefighter Earl Tolbert is helped into suit by Mike Bashore, David Seekford and Jack Spencer.At left, firefighter Jack Spencer uses tape to seal firefighter Earl Tolbert's protective suit. Above, Tolbert is rinsed off by firefighters Spencer, David Seekford and Stanley Taper. Below left,

hazmat technician Ruth Cade, left, and Lt. Robert Callahan enter building where powder was found in an envelope. Below right, Tolbert sprays himself with water during a decontamination exercise.