Even though you change the batteries in your smoke detectors every fall and spring, they may not perform when it counts.

A Texas A&M professor who has been sounding the alarm about smoke detectors for years says most devices on the market and in homes likely won't work fast enough to save lives during a fire.

B. Don Russell, Distinguished Professor with the Texas A&M Department of Electrical and Computer Engineering, has done experiments for news media using the two types of smoke detectors most widely available - those that use only ionization sensors and those that use photoelectric sensor technology.

There are also "dual-sensor" devices that employ both ionization and photoelectric sensors.

Although more expensive, dual-sensor smoke detectors and those that photoelectric technology alone are quicker to detect smoke from a smoldering fire, Russell said.

"Ionization smoke detectors are very slow to respond to dangerous smoldering fires that generate toxic gases," he said. "It's argued that over 90 percent of homes in America have only ionization smoke detectors."

Russell considers his smoke detector research to be a sideline, with his main area of interest being electric power systems, according to the A&M release.

"I maintain my interest in smoke detector performance because of the significance it has to public safety," Russell said. "Hundreds of people die or are injured each year in residential fires, too often because their smoke detectors did not provide a timely alarm."

Russell advises homeowners to scatter multiple smoke detectors throughout the home. Use detectors of both types or dual-sensor devices, he said.

A detector that has only photoelectric sensors is good for the kitchen because it won't sound a false alarm when cooking mishaps produce smoke, Russell said.

Many people are lulled into thinking their smoke detectors are very sensitive because they react to burnt toast, he said.

"Unfortunately, the smoldering fires that kill people don't have the same characteristics as burnt toast," he said.