What do atomic weapons and cigarette smoke have in common?" asked John O'Hara of Bowie as he stood before the Senate Finance Committee today holding a poster comparing a plume of cigarette smoke to the mushroom cloud of a nuclear explosion.

"Both kill and both have radioactive particles," said O'Hara, the president of his local chapter of GASP (Groups Against Smoker Pollution) and a supporter of a proposed bill that would make it illegal to smoke in public places in Maryland, including many restaurants, grocery stores and workplaces, except in designated smoking areas.

Supporters of the legislation, including doctors, a cancer specialist, public health officials and parents attended a jammed a public hearing on the bill today, recounting what one witness called the "ravages of tobacco smoke." Each carefully pointed out that they were not antismoking, just determined to protect themselves from what they say are the health hazards of "second-party smoke" they say is imposed on them by others.

Another group of speakers, including tobacco lobbyists, restaurant owners, and labor representatives, followed with equally stiff opposition to the bill, which they said amounted to an attack on the tobacco industry. The bill is so vague as to be unenforceable, they said, and would cause a nightmare of logistical problems as businesses tried to juggle locations for their smoking and nonsmoking workers and patron.

"The clear intent [of the bill] is to decrease sales of tobacco which will have a ripple effect" of layoffs, unemployment and increase dependence on state welfare payments, said Ray Scannell, a staff assistant for the International Bakery Confectionary and Tobacco Workers union in Kensington.

Bruce C. Bereano, the lobbyist for the Tobacco Institute who was paid $30,000 last year to help defeat a similar measure, told the senators that the bill, which he called an "attempt to regulate social behavior" was "thoroughly impractical" and would promote public confrontation between smokers and nonsmokers.

Laws regulating smoking in public places are already in effect in 34 states, this bill's sponsors say, but have consistently died in the Maryland General Assembly.

Yesterday, the future of the bill again appeared uncertain. This year, the bill is once again in trouble, said committee member Howard A. Denis (R-Montgomery), who voted for the proposed law last year but said he is now concerned about its practical implications. "This is the hardest look we've ever taken at the bill," he said.

But Sen. Stewart Bainum Jr. (D-Montgomery), who is cosponsoring the bill, said, "I'm optimistic my colleagues will see the benefit to public health."

The bill provides for a $25 penalty if an employer or owner fails to segregate smokers and nonsmokers or if a smoker refuses to quit smoking, and authorizes enforcement, either by a business owner, employer or ultimately the police, when a complaint is made about an offending smoker. Small restaurants that seat fewer than 49 people, work places with fewer than 11 employes, factories inaccessible to the public, private social halls, bars and bowling alleys are exempt from the bill's provisions.