White Ghost” explained
Albert J. Kirk
National Steel, Midwest Division
Portage, Indiana
I enjoyed “The White Ghost” (Frank C. Montagna, Training Notebook, May 1995) and the story line. Outlined below is some information I believe you will find of value.
Oil-burning furnaces come in many types, sizes, and fuel types. Some use a single-line fuel system. Others, due to the fuel tank location, use a two-pipe system for oil recirculation. Under normal operation, the thermostat calls for heat, the furnace starts without incident, and everyone is happy to have heat on a cold winter morning.
A modern furnace has various safety circuits and combustible gas-purge systems to prevent the firing of fuel in an unsafe condition. Unfortunately, we live in an imperfect world. Owners of furnaces bypass safety systems, and sometimes the safety circuits simply do not work even with the best of maintenance and intentions.
Hence, the call to an oil-furnace fire can be a complicated and potentially dangerous situation. The color of the smoke and ventilation practices commonly used by fire departments can actually aggravate the situation and need to be evaluated for safety at each fire scene.
Oil fires in furnaces can be caused by several problems. The most common are too much air; too little air; firing of oil without a flame; firing of too much oil; firing of too little oil; leaks in the firebox; leaks in the chimney; and, of course, improper owner modification of the furnace. Considering how complex and dangerous an oil burner really is, it`s a miracle that an oil furnace actually works reliably when so many things can go wrong.
Furnace fires most commonly are caused by failure of the fuel to ignite. Fuel may end up in the chimney, or leaks in fuel-oil piping may ignite outside the firebox. Fuel may also be overfed into the furnace firebox, leak out of the firebox into the furnace room, or be fed into the firebox when no fire/ignition is occurring. The first two situations are common and are routinely handled by fire departments.
They normally are accompanied by a small amount of visible flame and copious amounts of black or white smoke. Fire extension into the basement, walls, and attic surrounding the chimney is a definite problem. This type of fire is not likely to cause the “White Ghost,” since the fuel is burning or smoldering with adequate oxygen. This is a regular structure fire but was started by an accelerant (fuel oil) burning outside the firebox.
Fuel being overfed into a firebox with a furnace igniter firing and fuel being fed into a hot firebox without ignition can cause the “White Ghost.” This overfeeding of fuel into a firebox where some of the fuel is smoldering or free-burning can cause grievous problems.
Insufficient air (low excess air) prevents complete combustion of the fuel source, and smoky conditions ensue, which may or may not have visible flame. As time clicks by, excess fuel will accumulate inside the firebox, chimney, and anywhere else it can pool or coat. The burner continues to atomize and inject fuel oil into the hot firebox and chimney, increasing the heat and the total amount of unconsumed combustibles.
Meanwhile, oxygen levels continue to go down further, increasing the quantity of combustibles due to the smoldering conditions inside the firebox. As the elemental carbon from the oil residue and carbon monoxide continue to accumulate, the fire slowly smothers to a hot smoldering stage. Yet, with a live ignition source in the firebox in the form of the furnace electric igniter system, the igniter continues to attempt to light off the fuel oil. The low oxygen atmosphere, however, prevents proper or explosive combustion. Enter the unsuspecting firefighters.
They use the fog line and start to ventilate the basement. Suddenly, the fire has additional oxygen introduced by the fog line and basement ventilation. Cracks in the chimney and furnace firebox provide the furnace with a positive draft up the chimney. Now, depending on how much carbon monoxide and unburned oil are present, the fire will rise to the occasion and start generating white smoke mixed with fuel and cause an ignition (I do not believe it would be an actual backdraft in this case). At this point, the fire is free from the firebox, and the routine fire call now is a major exercise in “what happened?”
The other case is similar to the first but is even more dangerous. In this case, the furnace igniter may not be firing; therefore, the obvious ignition source is gone. The fuel oil, though, continues to be pumped and sprayed, atomized, into the furnace firebox. Carbon, unburned atomized fuel oil, and carbon monoxide collect in the furnace and chimney. Various leaks spread it into the building.
Copious amounts of black smoke are visible, and an observant incident commander notices that heavy black smoke is leaving the building chimney. This is important in that the furnace still has a positive draft from firebox to chimney to roof. Enter the unsuspecting firefighters.
They charge the fog line and open some basement windows. The smoke pours out. It`s black and some fire is visible. The radio says it`s real “hot,” but little fire is visible in the basement. You`re aware that it`s now a preignition condition, but everything seems to be going well.
Then the IC notices the smoke change from black to white, and you can taste and smell the fuel oil. You seem to be happy because fire service training indicates this is a positive thing caused by the fog lines and ventilation. You`ll be back to the station in no time. Yet, conditions actually have gone seriously downhill.
The oil pump continues to fire atomized oil. Suddenly, the IC looks at the roof chimney again and realizes “there isn`t any smoke coming out of the chimney.” Meanwhile, inside the furnace, oxygen levels are rising; and carbon monoxide, carbon, atomized oil, smoke, and extra oxygen are pouring out of every crack in the chimney, the furnace, and the furnace service door into the basement under pressure from a downdraft in the chimney.
Suddenly, the right mixture of heat, carbon monoxide, unburned atomized fuel, and oxygen occurs. The smoke flashes over or explodes. The fire rushes outward from the furnace, following the firefighter-made ventilation drafts. Every ventilation path, stairwell, and window suddenly becomes engulfed with smoke and heavy fire. The “White Ghost” has struck.
What happened is that the chimney draft reversed as a result of the firefighters` ventilating the building basement. At this point, copious amounts of fresh air move from the roof down the chimney into the firebox. The oxygen levels rise high enough to support combustion and a flashover, smoke explosion, or backdraft occurs as the superheated air now has sufficient oxygen and combustibles to ignite into visible flame.
The fire roars out of the furnace and chimney through the basement and follows the firefighter-made ventilation paths into the building and out the open windows. Instead of helping, the fog line actually has helped this to occur. The water from the fog line has trapped the excess heat as steam, and the cooling action has upset the normal air movement, causing the reverse draft in the chimney.
I hope this helps with research on the “White Ghost.” In my capacity as section manager of National Steel`s Midwest Division, I am an officer of the steel mill fire brigade. My duties include supervising the operation and maintenance of the mill`s gas- and oil-fired steam boilers, small building boilers for heat, high-voltage electric power, hydrogen and nitrogen gas distribution, water, wastewater, and hazardous waste. In my spare time, I`m an officer in the mill fire brigade, where I am an incident commander, a safety officer, and a member of the haz-mat response team.
