By Steve Tawa

PHILADELPHIA (CBS) — Philadelphia public safety officials not only remind us to shift our clocks back one hour this weekend, as Daylight Saving Time ends, but to check the effectiveness of our home’s smoke detectors.

Technically, legislation Mayor Nutter recently signed requires all one- and two-family homes to have ten-year, lithium battery-powered smoke alarms, as part of the city’s new fire code beginning January 1st (see related story).

“That early warning is critical,” fire commissioner Lloyd Ayers (at lectern in photo) told a community gathering today.

But realistically, he admits, he is aware that not everyone will immediately swap their current smoke detectors for the new type.

“In that transition, we still have perfectly good working smoke alarms out there that some folks are going to be using for a while,” the fire commissioner said today at the Center in the Park, on Germantown Avenue.

That’s why Red Cross CEO Renee Hughes was also pushing the “Change your clock, change your battery” slogan for this weekend.

“Change those batteries — the smoke detector will work. And when you can afford it, get a ten-year lithium battery (detector),” Judge Hughes said.

In 2011, officials say 34 percent of the homes in Philadelphia with fires had no batteries in their smoke alarms, and 22 percent had dead batteries.