Palo Alto has become the second city in California to require the installation of photoelectric smoke detectors in new homes and businesses.

The City Council voted unanimously Monday to mandate the use of the devices, following the lead of Albany. The fire chief of the East Bay city, Marc McGinn, is crusading to phase out the most common type of smoke alarms, known as ionization detectors.

Photoelectric detectors are believed to limit the number of false alarms prompted by such things as smoke from stoves and steam from showers. Some studies have shown they are better than ionization detectors at detecting smoldering fires before they turn deadly.

Palo Alto Mayor Pat Burt said members of the California Fire Chiefs Association had asked the council to delay its decision until the group completed its own study of the detectors.

"But they did not offer an opinion that found photoelectric was less safe, and we had significant testimony that ionization was less safe," Burt said.

The new requirement will take effect Jan. 1.

Photoelectric devices detect smoke once it has crossed a small beam of light. Ionization detectors contain a tiny bit of radioactive material that creates an electric current, and once that current is disturbed by smoke, the alarm sounds.

Photoelectric detectors typically cost $15, about $5 more than the ionization models.

"For a relatively few dollars, our residents can have what we believe is a safer system," Burt said. "This follows a steady increase in technology making people safer, and we needed to keep that ball rolling."