The D.C. City Council Tuesday delayed action on a bill that would require smoke detectors to be installed in new and existing residences and in many facilities in the city in order to allow time for the fire department to study a possible hazard of one type of smoke detector.

Council members recently were approached by groups that oppose the use of the ionization-type smoke detector. The groups said ionization detectors contain a possibly hazardous radioactive substance, according to council member David A. Clarke, who heads the committee that studied the bill. Clarke introduced an amendment that requires the fire department to study and make a recommendation on whether ionization-type detectors should be used. The amendment also requires the subject to go to public forum before the council can act on the legislation.

"We don't want to have a dangerous substance," required by law, Clarke said. "We don't have the information on this matter before us."

In its present form, the legislation does not point out which of two types of smoke detectors would have to be installed. The two varieties currently on the market are the ionization type and the photoelectric type.

The photoelectric alarm is triggered when its light beam is obscured by smoke. The ionization type detector is activated when a certain percentage of smoke particles are present in a room. Very simply, it "feels" smoke particles and its warning noise begins.

Rep. Ted Weiss (R-New York) recently sent a letter to Council Chairman Sterling Tucker and Mayor Washington asking the council to prohibit the use of ionization type smoke detectors. Weiss recently sponsored legislation in the House to prohibit the manufacture and sale of ionization smoke detectors, which contain a radioactive element, usually americium 241.

He said that while the ionization type detector does not represent a direct threat as long as it functions properly, "tests have shown that the thin protective foil housing the americium can be breached by fire and other types of friction and stress which can cause radioactive particles to be released into the environment." He also cited improper disposal of the detectors as a possible hazard.

Another group, called Mobilization for Survival, distributed letters urging the council to mandate the use of only non-ionization detectors. Consumer activist Ralph Nader has also spoken out against the use of ionization-type smoke detectors.

Under the bill, smoke detectors would be required in all existing and new homes in the city, as well as duplexes and apartments, hotels, motels, hospitals, nursing homes, jails, prisons and residential-custodial care facilities.

People who own homes here would have to install smoke detectors within three years of the time the legislation takes effect. Those who build new homes or residential facilities here or substantially rehabilitate them would be required to install smoke detectors beginning Oct. 1.

Smoke detectors also would have to be installed within two years by the District of Columbia in the facilities it owns and operates.