Leave Nicholas Keilen alone. That's all he asks. For 30 years, he has been a smoker and he says he is considerate of others when he decides to take a puff.

But last week, Keilen's courtesy began to matter very little, as Montgomery County's newest anti-smoking law took effect and prevented the General Electric telecommunications consultant from lighting up in his Rockville work cubicle. From now on, when he gets the urge to smoke, Keilen will either have to head outdoors or retreat to the first-floor room that serves as the company's official smoking lounge.

"I have no desire to quit, and it makes working conditions very difficult to go outside whenever I want to smoke," Keilen said as he stood, cigarette in hand, overlooking the Giant Food parking lot on North Washington Street. "I don't like the room they've set up for us. Bad ventilation, too full of smoke. I don't know what I'm going to do when it's not such nice weather."

Last week, Keilen and other smokers around the county began making adjustments in their work habits -- and some even in their cigarette habits. The word had gotten around, at least in some places, that as of May 24, smoking would no longer be permitted in employee restrooms, in company cars or in offices with more than two employees unless all consent.

In this latest effort by the Montgomery County Council to ensure a smoke-free work environment for anyone who wants it, affected businesses must either confine smoking to special areas -- enclosed with walls from ceiling to floor -- or order their smokers outside.

The law comes in addition to laws already restricting smoking in restaurants, public places and county buildings. As a package, the laws are believed to be the toughest in the nation. Nonsmokers said the new laws make a difference.

"My eyes were burning a lot and my clothes smelled from their smoke," said Tracey Madden, admissions representative at Technical Education Center Inc. in Rockville. "It's better already."

Some smokers are using the latest prohibition as an opportunity to stop, but others, such as Keilen, feel almost hunted as they try to comply with the law and find an acceptable place to smoke.

"It's a filthy, disgusting habit," said pack-a-day smoker Brian Rapp, a teacher at the Technical Education Center. "I tell people I used to smoke Camel non-filter and now I'm down to a cigarette with so little tar it's like smoking air. And, yes, here I am outside twice in a half-hour . . . smoking air. People see me coming back and forth into the office, back and forth."

One of Rapp's colleagues at the technical school, Jevita deFreitas, said the new law is a "good reason to quit." She said she had taken only "one puff" in the two weeks since the school put up the "no smoking" signs, and she can't smoke at home because her roommates don't allow it.

Gordon Martin, the school's director, is 41 years old and has been a smoker since age 16. With the top job comes the privilege of his own office -- and with the new law, permission to smoke if the door remains closed.

"That wouldn't be fair, so I'm not smoking in here either," he said.

Certainly, not all offices are aware of the new rules, as some workers continue to smoke in open offices and lunchrooms. The county Health Department, charged with enforcing the law, will not make random inspections. Instead, officials will investigate complaints from workers who don't believe the law is being followed in their offices. Roz Garfinkel, the department's chief of program operations, said the names of those contacting the county will not be made public.

Several businesses in the county have had smoking guidelines in place for years, and are using the new law to go further. For example, even those with private offices at the Marriott Corp. in Bethesda are now prohibited from smoking. Like many companies, Marriott will pay for its workers to attend smoking cessation classes.