On Inauguration Day last month, while subzero winds forced the president's celebration indoors, members of the Fairfax fire department's Hazardous Materials Response Team fought to stop the flow of 30,000 gallons of highly explosive liquid propane from a railway car of a Fairfax gas distributor.

The propane leak was only one of about 200 incidents involving hazardous chemicals that the county's special force has dealt with since it was formed 16 months ago. Hazardous material response teams are the newest wave of specialization in fire departments across the country, according to Capt. John P. Kimball, who heads the group referred to as the Haz Mat Team.

Fairfax Fire Chief Warren E. Isman, a nationally recognized expert on hazardous materials, said there's been a heightened awareness of accidents recently because federal and state laws now require chemical spills of 50 gallons or more to be reported.

"In the past, before it was recognized the kind of harm caused by hazardous substances, they were thrown away in the regular trash, swept up, or tossed into a dumpster. In the very, very recent past we've realized that we cannot dispose of the chemicals carelessly," Isman said.

After leaking methyl isocyanate killed at least 2,000 people at Union Carbide Corp.'s pesticide plant in Bhopal, India three months ago, there has been an increased awareness among state and federal officials about the possibility of similar accidents here, according to spokesmen for the Environmental Protection Agency. The EPA set up a task force to review laws to "squeeze out another inch of safety" in the chemical industry, said EPA spokesman Dave Cohen.

In Northern Virginia there are a number of areas where potentially hazardous chemicals are located. In the Newington area on I-95, five companies, including Exxon and Gulf, pipe in kerosene, fuel oil, gasoline and other petroleum products into tanks that hold tens of millions of gallons, Isman said.

And as the planting season gets under way, Isman noted, farm pesticides and fertilizers will be stored in bulk in Vienna, Fairfax, Chantilly and Alexandria for distribution in the spring.

Fairfax's full-time Haz Mat Team of 18 men is located in Fire Station 34 in Oakton just off I-66. Three auxiliary teams are at fire stations located in McLean, on Edsall Road and in the Penn Daw area of the county, south of Alexandria. As many as 50 men can be called to battle hazardous situations involving anything from chlorine gas to radioactive cobalt 60.

Last month, the Oakton fire station started using a truck specially adapted to deal with industrial and chemical accidents. A heavy rescue squad truck formerly equipped with a water pump and a winch for separating vehicles in traffic accidents was completely revamped by the fire department's apparatus division shop.

"To completely build a new unit from the ground up would have taken two years and cost about $200,000. We got a vehicle for the fraction of the cost," Kimball said.

Inside the red-and-white truck, five tons lighter after modification, a sleek aluminum interior serves as a field command post with equipment that includes a Geiger counter, chemical and gas detectors and acid suits.

Above a window-side desk in the truck sits the core of the Haz Mat Unit: books. Several key manuals allow the team to identify possibly life-threatening hazardous substances. Kimball said that identification of a chemical is the "utmost priority" from which all subsequent actions are determined.

Because accidents involving dangerous chemicals often happen on interstate highways or railways, one manual lists numbers that transporters must post on the outside of their trucks or rail cars to identify the substances inside. The guide describes the chemicals, possible dangers and what first aid should be used if they are inhaled or come in contact with skin.

"We're certainly seeing more truck accidents on the Beltway. We've seen an increase in industrial accidents, but not a big increase," Isman said.

The Haz Mat Team also must know when and to what extent people must be evacuated from unsafe areas. Last April at Trans-Circuit, Inc., which makes printed circuits at Baileys Crossroads, hydrogen and chlorine gases were emitted in a chemical boil-over. Two city blocks were evacuated and 18 people were sent to the hospital with nose and throat burns, said Lt. Rogers Herbstreith of the Haz Mat Team.

In another accident, part of I-66 was closed when a truck from New Jersey started leaking a chemical known as toluene, a flammable, toxic liquid. The Haz Mat Team escorted the truck to the Fire Training Academy on West Ox Road, where the truck was impounded and the leak stopped.

"Anything that travels north and south travels through this area. It comes through the county," Herbstreith said.

Firefighters use butyl rubber acid suits when entering contaminated areas to stop the flow of hazardous chemicals. It takes two men to help don the bulky orange suits, which resemble astronaut gear. A special cooling vest and an air pack that lasts an hour are attached to each suit to prevent poisonous air from getting inside.

Kimball lifted a gray tarpaulin off one of the suits in the truck.

"We treat these things like babies, because our lives depend on them. Ideally they're impermeable to chemicals -- a wide range of acids," Kimball said.

A Geiger counter and an alpha meter can detect radiation, and an explosion meter will alert the Haz Mat Team if a substance is explosive. Tools and valves are kept in the truck to close off leaking pipes.

Most fire departments in the metropolitan area, including the District, Montgomery County, Prince George's County and Alexandria, have special hazardous matter squads. Fairfax has the largest one, Kimball said. The Fairfax Haz Mat Team also responds to emergencies in Prince William, Loudoun and Arlington counties, Kimball added.

To become part of the unit, firefighters are required to take college courses in chemistry and hazardous materials. Those who join take a 13-week class in hazardous substances at the Fire Training Academy. Because the field is relatively new, members also are sent to the National Fire Academy in Emmitsburg, Md., U.S. Coast Guard Training Center in Yorktown, and the Environmental Protection Agency in Edison, N.J.