After every fatal fire in Baltimore, including a blaze that took the lives of three children Friday, fire officials remind neighbors of the importance of smoke alarms.

Since their introduction in the 1970s, the devices have saved thousands of lives. But a growing number of experts now say that the best-selling and least-expensive smoke alarms in U.S. homes react so slowly to certain smoldering fires that the devices can go off too late for occupants to escape with their lives.

Critics say these "ionization" alarms are also too quick to sense cooking smoke, so their owners are two to six times more likely to disable them. Removing the batteries to silence these "nuisance" alarms leaves residents with no working alarm.

"Every night before I fall asleep I say a prayer for the two or three people I know are going to die that night because they have the wrong smoke detector," said Deputy Chief Joseph M. Fleming of the Boston Fire Department.

Fleming is an outspoken advocate for alarms that use an alternative "photoelectric" technology to sense smoke. Photoelectrics cost slightly more, he said, but they're quicker to sense smoldering fires and less prone to nuisance alarms. Although ionization alarms are faster at detecting flaming fires, he said, the advantage is a small one.

Maryland fire safety officials acknowledge the advantages and disadvantages of each technology. But they're reluctant to say anything that might discourage people from installing and maintaining any alarm.

"Far more people perish because they don't have any smoke detectors" than because they have the wrong kind, said Capt. Raymond C. O'Brocki, head of Baltimore's Fire Prevention Bureau. "It's not a question of good and bad. It's good, better and best."

Boston's Fleming does not hesitate to criticize. He suspects that tardy or disabled ionization alarms might have been a factor in up to a quarter of the fire deaths in Massachusetts - and might explain why some victims die even when alarms are present.

Investigators have not determined what started Friday's fire on Springdale Avenue or whether the smoke alarm they found had gone off.

After an electrical fire in December that killed two Roland Park children, they were similarly uncertain. Last summer, three young people died when a vacation home near Easton caught fire. By the time alarms sounded at 2 a.m., survivors said, the house was full of smoke and flames.

In all, 93 people died in Maryland fires in 2007, the deadliest year since 2001. Only 23 died in structures where smoke alarms were operational. Thirty-four died in Baltimore alone, but only three in homes where smoke alarms are known to have sounded, according to fire marshals.

National campaign

Fleming has been crusading nationally for fire and building codes requiring photoelectric alarms, in the wake of a 1990 Boston fire that killed five people when occupants of the home disabled their ionization device to stop nuisance alarms.

He subsequently learned that photoelectric alarms are less vulnerable to the problem because they're less sensitive to the small-particle smoke from flaming fires.

"It started to occur to me: Wait - if these people who took the battery out had had a photoelectric, they'd be alive today. They didn't have to die," Fleming said.

By 1998, he had pushed Massachusetts to alter its building code to require photoelectric alarms near kitchens and baths. (Steam, too, can trigger ionization alarms.)

Then he found studies showing that photoelectrics are also much quicker to detect smoldering fires - the kind most likely to catch people asleep. So he began working to have ionization alarms written out of Massachusetts' building and fire codes entirely.

One 2004 study by the National Institute for Standards and Technology (NIST) that Fleming cites found that ionization alarms can leave occupants just seconds to escape a smoldering fire before conditions become unsurvivable.

In some circumstances, conditions during test fires became deadly before the ionization alarm sounded. Fleming estimates that 25 percent of the fire deaths in Massachusetts occurred because people had ionization smoke alarms that went off too late or that had been deliberately disabled.

Massachusetts has responded to the message. Its building and fire codes were amended in January to require installation of photoelectric alarms in new or renovated buildings and in all homes at the time they're sold. The change is awaiting the governor's approval.

Lawmakers and fire officials in Vermont, Tennessee and Indiana - where Fleming has carried his crusade - are also studying the issue.

Maryland's codes require approved smoke alarms in every home. In new construction, that means interconnected alarms with battery backup on each level and at every bedroom. But the language is silent about the choice of technology.

Each has its advantages, said Maryland Fire Marshal William Barnard. But "we would certainly recommend that, for the optimum protection ... [Marylanders] utilize both technologies."

The International Association of Fire Chiefs, the U.S. Fire Administration and the Maryland State Fire Marshal now recommend installation of both photoelectric and ionization alarm technologies in American homes.

In Baltimore, O'Brocki said the city agrees.

Despite the apparent unanimity, ionization alarms remain the overwhelming best-sellers and, not coincidentally, the cheapest alarms on the market.

Baltimore firefighters continue to distribute and install 14,000 to 20,000 free ionization smoke alarms in city households each year - even though state law requires residents or landlords to do it on their own.

More expense

"It's a massive undertaking" without city funding, said Chief Robert G. Doedderlein, the city's fire marshal. "We're constantly looking for funds."

Now, they're seeking grant money to cover the higher cost of dual-technology alarms.

Ionization alarms retail for $5 to $10 but cost the bureau only $2.99 each. Photoelectric alarms retail for about $20 but they're hard to find in some retail outlets. They're available online at Google, Amazon and Lowe's Web sites. Dual-sensor units, combining both technologies, are readily available in stores and sell for $20 to $30.

Many fire officials and researchers are reluctant to speak ill of ionization alarms; whatever their shortcomings, they save lives every day.

Ionization alarms use a tiny radioactive source to create electrically charged gas molecules, called "ions," that enable an electric current to flow inside the unit. When smoke particles neutralize enough ions to interrupt the current, the alarm sounds.

Photoelectric alarms go off when enough smoke particles are present to reflect part of a light beam onto a photo detector.

NIST researchers have also found that modern materials burn faster and hotter, with more toxic smoke than common materials of the 1970s. So today's smoke alarms leave occupants 17 percent less time to escape flaming fires and 47 percent less time to flee smoldering fires.

The problems arise in those cooler, slow-smoldering blazes, the kind caused by electrical shorts or a cigarette dropped between couch cushions. Data cited in the study show that 42 percent of deaths occur in smoldering fires.

"In some situations ... there's not enough time to escape. Yet that's the whole point of having a smoke alarm," said Thomas G. Cleary, a NIST research engineer.

In contrast, the study's photoelectric alarms sounded 55 minutes before conditions became untenable.

NIST officials told the Boston City Council's Public Safety Committee in August that "ionization alarms may not always alarm, even when a room is filled with smoke from a smoldering fire." Scientists have reached similar conclusions in Norway, Australia and England.

Although dual sensor models would seem to be the solution under most conditions, Fleming argues against them near kitchens or bathrooms, where cooking smoke or steam might still provoke nuisance alarms from the unit's ionization detector. Those locations should have photoelectrics only, he says.

The National Fire Protection Association likewise recommends photoelectrics within 20 feet of a cooking appliance.

frank.roylance@baltsun.com

Smoke alarm tips

Maryland Smoke Alarm Law

At least one smoke alarm is required in every occupied residence built before 1975. Occupants of one-, two- and three-family dwellings are responsible for their installation and maintenance. Landlords are responsible in larger, multifamily structures.

Homes built between 1975 and 1989 must have at least one permanently wired smoke alarm installed in each sleeping area.

Homes built after 1990 must have smoke alarms on each floor and outside each sleeping area. They must be hard-wired and interconnected, with battery backup.

[Source: Maryland State Fire Marshal]

Best smoke alarm practices

Smoke alarms must be regularly tested and properly maintained. But fire officials say too many people don't bother. Here's how:

Test each of your alarms once a month.

A "chirping" sound means the battery is dying.

Replace batteries once a year. Some new alarms come with batteries guaranteed for 10 years, after which the whole unit should be replaced.

Vacuum your alarms once a year to remove bugs, dust and cobwebs.

Replace your alarms every eight to 10 years, whether wired or battery-operated. Replacement units are available, in stores and online, for both types. They can often be installed with existing ceiling plates and electrical connectors.

Never remove alarm batteries except to replace them. If cooking repeatedly sets off your alarm, move it 20 feet from the stove or replace it with a photoelectric alarm.

Safety experts recommend interconnected alarms that go off simultaneously when even one senses smoke. No wiring may be necessary: there are wireless, battery-operated models on the market.

Some alarms are now available with "Hush" buttons. If set off by cooking smoke, they can be silenced for 10 minutes without removing the battery.

Researchers say children and adolescents who might sleep through a smoke alarm's warble will often respond to their parents' voice. Some new alarms can record verbal escape commands and play them back - loudly - when they sense smoke.

[Source: U.S. Fire Administration, Sun reporting]

Have an escape plan and rehearse it

Know two (2) means of escape from any room in the house.

Always check a door to see if it is hot before opening it to escape.

If you must go through a smoke-filled area, crawl on hands and knees for less exposure to smoke and heat.

Decide in advance on a pre-arranged location outside of the house to meet, so you can count occupants and be sure everyone is safe.

[Source: U.S. Fire Administration]