Fire Stopping Credited With Reducing Hazards

The May 4 fire at the First Interstate Tower and the July 18 blaze at the Union Bank Building point out the need for sprinkler systems and proper fire stopping in high-rise and other buildings.

Fire stopping?

The key word is compartmentalization, according to A.D. Boche, a fire protection products specialist at 3M in St. Paul, Minn.

Active elements, such as sprinklers and passive products that seal floor and wall penetrations--fire stops--help keep the fire contained, he said in an interview in Los Angeles.

Neither building had sprinklers--they were being retrofitted to both--but a preliminary investigation following the fires showed that the older-style, compartmentalized design of the Union Bank building helped limit injuries to one person and restricted the fire to the 34th and 35th floors, while the newer open-plan design of the First Interstate Bank tower permitted the fire to spread from the 12th to the 15th floors and take the life of one worker and injure 40 more.

Education--for building inspectors, contractors, architects and owners--is a key to greater use of the latest technology in fire-stop caulking, pipe seals, sheet material and other products designed to keep smoke and flames from quickly spreading from one floor to another, according to Michael E. Burke of 3M’s Los Angeles contractor products office.

Burke is currently conducting meetings with Los Angeles building inspectors to inform them of proper fire-stopping material inspection techniques.

“Phoenix and Miami have already conducted similar seminars and have written clear, easy-to-read specifications so the field inspectors can make sure the contractors properly install fire stopping,” according to Boche. He conducted the seminars in Phoenix that resulted in the new guidelines for designers, inspectors, contractors and owners.

The most advanced fire-stop materials--and the most effective--are those with intumescent characteristics, listed by the Underwriters Laboratory (UL) and approved by model building code groups, Boche said.

“Intumescent materials, composed of synthetic elastomers, expand when heated, eventually becoming a hard char,” he said.

“Where pipe insulation or plastic pipe is consumed by fire, the fire-stopping material fills the cavity and keeps it closed, preventing the smoke and gases from spreading to other floors.”

Curtain-wall construction, widely used in high-rise structures, creates a gap between the structural steel in the middle, the curtain wall that is fastened to the steel and the floor. Composite sheet material, with intumescent characteristics, is used to bridge this gap, Burke said.

He added that fire stopping should be considered a major priority for building owners and managers who are renovating buildings.