Smoke Alarms May Not Work In A Pinch

Household fire extinguisher and smoke alarms
AP / CBS
When a jury this spring concluded a smoke alarm failed in a fatal upstate New York house fire, safety experts were already questioning whether popular models meet the threat posed by fast-burning synthetic materials now common in American homes.

The federal court jury found the design of popular "ionization" smoke alarms defective in the fire that trapped William Hackert Jr., 56, and his 31-year-old daughter Christine in their house near Albany in 2001. Survivors contended that First Alert and its manufacturing subsidiary BRK, which control 85 percent of the market, continued to make and sell millions of the cheaper ionization detectors despite knowing their disadvantages.

There are two common types of smoke alarms:

  • Ionization alarms, which detect smoke with the help of radioactive material, sound earlier in fast-burning flaming fires.
  • Photoelectric alarms, which detect changes in light patterns, sound earlier in slow smoky fires, which take time to transition to flames.

    Under longtime national standards, either alarm is acceptable. Experts say both save lives, but the time needed to escape once flames start has gotten dangerously short, particularly for the disabled or impaired, because of fast-burning synthetics in furniture and carpets, and standards may need to change.

    Consumer Reports in 2001 recommended that homeowners install at least one ionization and one photoelectric alarm on every level of a house to improve warning times for different types of fires. An April report from the Public/Private Fire Safety Council went further, noting that some test escape times were "tight or insufficient" with either alarm for bedroom or living room flaming fires. The group suggested that Underwriters Laboratories modify its standard to require faster detection of smoldering fires.

    Current UL smoke alarm standards, first developed in the 1970s, require alarms to respond within 4 minutes of a flaming fire and in a smoldering fire before smoke obscures visibility by more than 10 percent per foot.

    In today's homes, the tendency for synthetics — like nylon and polyester in furnishings, fabrics and carpeting — is to smolder for a long time, then burn faster than natural materials like wood and cotton, which char as they burn. Synthetics melt and pool, then give off substantially more energy when they burn, said Tom Chapin, head of UL's fire protection division.

    That has shortened the time to "flashover" — from first flames to combustion of the entire room due to accumulated heat and gases — from an average of 12 to 14 minutes 30 years ago to about 2 to 4 minutes now, Chapin said.

    "In the flaming scenario, the escape times are radically shorter," he said.