Fairfax County, in an effort to reduce drunk driving accidents, yesterday announced it will increase police road patrols during the holidays and equip officers with $40,000 worth of new portable breath-testing devices.

Police Chief Carroll D. Buracker said that while the new cigarette-size breath-testing devices have not yet been approved for use as evidence in Virginia's courts, they will help officers determine if a driver has been drinking. Suspected drunken drivers then may be tested on the standard breathalyzer, which can be used in court, police said.

"We are out to solve the drunk-driving problem to the best of our ability," said John F. Herrity, chairman of the Fairfax County board.

Yesterday's press conference followed a recommendation made earlier this week by the Metropolitan Washington Council of Governments urging that the District, Maryland and Virginia take steps to curb drunk driving and require the use of seat belts in cars.

Montgomery County police are planning holiday season roadblocks to catch suspected drunk drivers.

District police, in addition to increased patrols, will also use roadblocks, starting tonight at 11 p.m.

Buracker has opposed the use of roadblocks, saying they are not an efficient use of police manpower.

In Fairfax, the number of accidents involving alcohol has dropped from 36 in 1981 to 27 last year and 15 during the first nine months of this year.

Also the number of persons killed in alcohol-related accidents has dropped, from 37 in 1981 to 28 last year and 17 during the first nine months of this year.

County officials yesterday also announced the hiring of a $26,500 coordinator for the county's drunk-driving prevention and detection programs. The coordinator, Jerry D. Stemler, 44, is a former director of highway safety for the state of South Dakota.