PYROLYSIS DANGER IN HOUSING DEVELOPMENT
BY RANDALL D. LARSON
Two house fires that occurred in late 1993 in a residential tract of nearly 300 homes in south San Jose`s Almaden Valley kindled the interest of San Jose fire investigators. It was discovered that conducted heat from forced-air furnaces that were faulty or improperly designed or mounted caused the fires. Since the fires had identical causes involving ceiling-mounted heating systems with identical configurations, concerned firefighters brought in city building inspectors to verify the safety of the homes in the housing tract. The houses in the development are large and close together. The outer ring of the tract features 4,000-square-foot model homes surrounding two inner circles of 2,000-square-foot homes. Both fires occurred in the inner circle.
These incidents and the ensuing investigation highlighted how important it is for fire departments to know what resources in other city departments are available to them and to work with these departments to resolve potential hazards.
The first fire occurred shortly after 2 p.m. on November 6, 1993. Homeowner Ronald Payne called 911 from his residence on Quail Creek Circle to report a fire in his attic. Fire Communications dispatched an alarm assignment consisting of Engines 22 and 28, Truck 13, and Battalion 13.
Captain Tom Richardson, on first-due Engine 22, arrived within six minutes and reported that there were no flames but some smoke showing from the exterior. He and his crew entered the building and found no visible sign of flame. After opening the ceiling gypsum board, a small amount of smoke was emitted, and the crew noticed that ceiling joists surrounding the attic-mounted furnace had been slowly burned over a period of time until the gradual smoldering alerted the homeowner to a problem.
Richardson canceled all but the second-due engine company, and the crew pulled down gypsum board to expose the full extent of the damage caused by the furnace. The crew jimmied up the corner of the furnace, which was on a galvanized metal plate resting on top of 38-inch plywood, which was resting on top of the ceiling joist. They found that all the 2 ¥ 6s underneath the furnace were gone, indicating that fire–or this heating process–had occurred over two or three winters. Every time the homeowner turned on the furnace, “it was cooking those ceiling joists out,” Richardson explained.
The problem was determined to be pyrolysis (a chemical change brought about by the action of heat). An insufficient amount of air exchange prevented the breakout of a fire. Engine 22`s efforts were mainly in overhaul and investigation.
The incident alerted Richardson to the potential fire danger in the housing development. In his report, he listed the furnace as the cause of the fire. He noted: “The furnace`s internal combustion chamber was so close to the exterior sheet metal of the furnace that the… [conducted] heat ignited the surrounding wood products.” The furnace was supported in the attic only by 2- ¥ 6-inch ceiling joists. The sheet metal outside of the furnace was so hot that the 2 ¥ 6s ignited; the plywood between them also burned.
His concern that this condition might exist elsewhere in the development led Richardson to remain involved with the situation.
Payne called in an independent inspector, who examined the furnace in his house on four occasions, once in the company of Richardson and the Engine 22 crew and a representative of the furnace manufacturer. The furnace was fired to test its operation and then was dismantled.
The inspector`s report verified that the furnace caused the fire. Instructions for installing the furnace permitted it to be installed in an attic, a crawlspace, or an alcove, and the clearances specified by the manufacturer were properly maintained. The inspector found that two holes in the bottom of the furnace`s heat exchanger caused the fire. Their locations, he explained, were such that they caused them to act as nozzles, blowing fan-forced air straight down onto the burners beneath. He cited poor-quality welding. Tack welds on the heat exchanger below the burners opened, allowing intense heat to concentrate on the bottom of the furnace and allowing heat to be conducted directly to the plywood. The heat then ignited the plywood on which the furnace rested. Zero clearance was found between the furnace and the plywood. The inspector recommended that the homeowners` association have all furnaces similar to the one in Payne`s house checked for similar damage.
Payne fired off a letter to the development agency that built the housing tract, alerting it to the apparent defect in the furnace, and asked that the premises be inspected.
Richardson sent letters to the homeowners` association and the builder stating the department`s concern about the potential fire hazard posed by the furnaces. Among Richardson`s comments were the following: “On investigation as to the cause, it was determined that the furnace had caused the fire. Whether the furnace was improperly manufactured; roughly handled before or during the installation; or otherwise improperly designed, manufactured, or installed has yet to be determined. The San Jose Fire Department recommends the immediate inspection of all furnaces installed above ceiling level, to preclude the possibility of a fire occurring in defective units.”
Since the fire department did not have the authority to demand compliance with these recommendations, it concluded its investigation by referring the matter back to the homeowners` group.
At 5:30 p.m. on December 17, 1993, a woman living two doors down from Payne`s house called 911 asking for the fire department. “I just woke up, and it smells like there is a fire in the house,” she told the fire dispatcher. “I`ve looked all over the place and I can`t find a thing; but there`s a terrible odor, and I hear the roof crackling. Our neighbor had a fire a month ago because his heater got on fire, so I`m getting worried that maybe that`s what`s happening.”
Although a different shift was on duty, crews and dispatchers were familiar with the peculiarities of the first fire. Arriving on scene, Engine 22 found active fire in the attic. Engine 22, with the assistance of Engine 28 and Truck 13, extinguished the fire with 100 feet of booster line and 50 gallons of water. Battalion Chief John Flatley ordered extensive overhaul, specifically the pulling down of ceiling sections to check for fire extension and to inspect the furnace area. Captain John Skeen, commanding Engine 22, reported that “the fire was caused by a poorly designed or faulty heating furnace that is mounted in the combustible attic area with almost no clearance to wood roof supports.” Skeen recognized that the circumstances were identical to the November 6th fire, except that the damage caused by the furnace was more extensive: Pyrolysis extended down into the wall. Skeen recommended in his report that all heating units in the development be checked for fire safety.
After having been apprised of the similarities between the two incidents by Fire Communications, Investigator John Pieper responded to the fire scene. Henry DeGroot, the fire department`s public information officer (PIO), also was notified and, within hours, had contacted the city`s Building Department of the potential hazard.
On December 20, Richardson and Captain Earl Santos (Engine 22 during this shift) met with Phil Ribbs and Gene Stone, city mechanical inspectors. After reviewing the circumstances, Inspector Ribbs decided to do a random inspection of homes with similarly configured furnaces. All went out to the tract and inspected two homes with ceiling-mounted forced-air furnaces. Inspecting the limited areas they could observe without dismantling any portion of the furnace, they found that the heat exchangers and the burner showed signs of deterioration. In addition to damaging the wall, they found that the pyrolysis also damaged smoke detectors protecting the hallways. Stone observed that the heaters had burned the detectors` wires, “killing” the detectors. The inspectors, after checking several furnaces, confirmed the fire department`s opinion–and that of the private inspector who had tested Payne`s furnace–that the heater as installed contained an inherent and hazardous condition. They agreed with the fire department that the fires could have been smoldering for months.
Inspector Ribbs contacted the manufacturer of the furnace and the builder of the homes, asking them to correct the problem; no further assistance from the fire department was requested.
The manufacturer came in to test the heaters. “Then all of a sudden,” Stone reports, “the main office got involved and took over.” The furnace manufacturer and home builder brought in teams of inspectors, who checked the condition of the furnace at each residence. At least 60 defective furnaces were identified and replaced.
One of the difficulties encountered was the parties` reluctance to accept responsibility for the problem because of the fear of litigation. The furnaces had been partially manufactured in the United States. The steel stampings had been shipped to Mexico for assembling and welding and then were returned to the United States as complete units. The exact cause of the furnace breakdown remains in dispute.
LESSONS LEARNED AND REINFORCED
These two fires and the hazardous potential they represented underscored the need for the fire department`s working closely with the city`s building and mechanical inspectors and the homeowners living in the development. The sequence of events–reporting of the fires; extinguishment, investigation, follow-up by the fire department; follow-up by the resident; and inspection and follow-up by building inspectors–illustrates that issues involving mechanical hazards discovered as a result of a fire can be resolved. Lines of communication between the fire and building departments must be kept open–departments should not act independently.
Even though Richardson had suggested that the furnaces be inspected immediately after the first fire, it took a second fire, which occurred more than a month later, to get meaningful action. Bureaucracy and red tape can confound follow-up until circumstances reveal the situation to appear urgent. After the second fire, the fire department was able to bring in the city`s mechanical inspectors, who had the authority to implement an inspection of all the furnaces in the complex and to ensure replacement of faulty units. If this had been a fire in a single residence, the fire department could have gone back to the builder and handled it more quickly. But since it was a development and so many people had to be contacted, it took a lot longer. Once it became apparent that there was a problem, correcting it became a priority for all participants.
Not much could have been done in this case as far as prevention was concerned. Once it became obvious there was a problem, the city`s mechanical inspectors contacted everyone involved and asked them to come out to make an inspection. The mechanical inspectors were allowed to spend as much time as was needed in the field, at no cost to the homeowners.
Other departments make additional resources and expertise available to the fire department. For example, points out PIO DeGroot, “There`s nothing in the fire code I know of that gives us the authority to inspect individual homes. Under the Mechanical Code, however, the Building Department has a way of accessing that [code].” He notes also that these agencies deal daily with builders` and homeowners` representatives, making them more adept at handling these matters.
The incidents reinforced the importance of collecting and correlating fire data. If members of the two different shifts hadn`t communicated with each other, or if dispatchers hadn`t recognized the similar circumstances and relayed that information to investigators, the potential for a problem might not have been recognized.
Dealing with other city departments was new to the fire department, notes DeGroot: “The fire department should know whom to contact, how to get the word out about the hazardous situation without unduly alarming homeowners, and the appropriate action to take in a given circumstance. It all falls under the umbrella of municipal services–that`s why we have individual departments,” DeGroot points out. “It benefits the entire body when the left hand knows what the right hand is doing.”
A recent budgetary move by the fire department presented an advantage in this regard. In relocating its Building Plan Review Section from the Fire Prevention Bureau to the Neighborhood Preservation Department at City Hall, the fire department can work more closely with inspectors such as Ribbs and Stone. The departments now can communicate one-on-one to share information that ultimately can lead to quick action against the kind of hazard Engine 22 confronted on Quail Creek Circle. n
RANDALL D. LARSON is a communications supervisor for the San Jose (CA) Fire Department and has more than 10 years of experience in public safety dispatching. He is secretary for the California Fire Chief`s Association–Communications Section (Northern Division) and a freelance writer. His articles on the fire service and emergency communications have appeared in numerous publications.