A gas furnace with a good heat exchanger will NOT produce carbon monoxide and my family is safe. (Dead Wrong!)
A good heat exchanger in a furnace is NO indication of your safety!
Most carbon monoxide poisoning incidents occur in situations where the furnace and water heater were both operating correctly and were intact! The problem is usually found to be issues with combustion air or a blockage in a flue or chimney. Sometimes the installation is faulty.
To assume you’re safe just because someone says your heat exchanger is “OK”, but doesn’t check the rest of your home, is pure folly!
Give me 15 minutes in your home and I can have ANY furnace with a good heat exchanger producing enough carbon monoxide to put you to sleep – permanently. And, I’ll guarantee I’ll never touch the furnace itself.
Here are a few real-life examples:
Attic Fan Kills Teenage Partiers
Teenagers were having a party in a modern house. Due to the excessive cigarette smoke, they turned on the whole-house attic fan for approximately three minutes. Everyone left except for two boys who slept over in the house. One never woke up again. The cause of death … carbon monoxide poisoning.
The teenagers were having their party on an extremely cold winter night, so all the windows and doors were closed tight. The gas appliances in the home had been present for 15 years and were still operating fine after the poisoning. However, when the whole-house fan was turned on, it reversed the flow down the flue pipes; instead of up.
This also caused the furnace burner to operate improperly and produce large amounts of carbon monoxide, which dumped into the living quarters. Within three minutes, the carbon monoxide level throughout the home was 300 ppm. When the attic fan was turned off, the gas burner returned to normal operation. This concentration was not high enough to cause any ill effects to the partygoers by the time they left. However, the concentration was high enough for continued exposure to cause a build up in the blood of the two young men who remained.
The carbon monoxide level in their blood slowly increased until one young man died and the other was put in the hospital. Carbon monoxide incidents are usually caused by several factors combined. Very rarely is it caused by the “furnace failure” often noted by the gas company or fire department. Typically in buildings, most of the factors involve improper installation and/or lack of maintenance. Gas appliances can usually operate fairly well for years until that one time when something changes. This one additional factor is often “the straw that breaks the camel’s back”. The additional factor may allow the incident to occur, but is often not the primary cause.
Office workers Sickened by Improperly Installed
Flue and Return-Air Duct
Several people were starting to feel ill in an office building in an eastern city. The heat exchanger of the furnace had been replaced only two years before. They called a heating contractor. He found a cracked heat exchanger and red tagged the furnace. A lawsuit was filed against the furnace manufacturer.
Careful examination and testing indicated 14 separate problems, either related to original improper installation or poor maintenance. The heat exchanger was found cracked, however, this alone did not cause the poisoning. The blower position was such that even though there was a crack, no carbon monoxide entered the heated air. Furthermore, the crack resulted from not installing the new burners, which accompanied the new heat exchanger. The old burners were corroded, causing an improper flame pattern. The improper heating of the heat exchanger caused it to crack. A heating contractor replaced the “one shot” flame roll-out switch with an auto-resetting type. Thus, this furnace continued to cycle off and on in this improper state. However, these factors were not the primary cause of the poisoning.
The primary cause of the poisoning was two fold. The flue pipe exited the structure horizontally, out into a basement stairwell. The rectangular hole cut through the masonry wall was never properly sealed and large gaps were present. The second factor were holes cut in the cold air return duct for the furnace in the basement. This created negative pressure throughout the basement. Thus, the exhaust gasses in the basement stairwell were suctioned back into the basement, into the cold air duct and blown out with the heated air.
Carbon Monoxide Cases Investigated by
Thomas L. Liston, P.E.,
Case: A young couple and their three children were hit by carbon monoxide in their rented house in Napa, California on 12-07-2010. PG&E found heater’s flame recirculating. Heater was Williams Model 2509612, but it was grotesquely modified. The burner was twisted to a non-horizontal, inward-facing direction. The control valve was an incompatible type meant for former Williams models having no provisions for connecting a spill switch. The spill switch was disconnected by snipping of wiring. Former home owner swears it came out of the box that way. It seems that three generations of former owner’s family lived for at least a decade with that heater and did suffer accordingly.
Client: Julia Swanson Law Office of Beverly Hills, California
Side: Plaintiff. 2012.
Case: Middle aged woman complained of carbon monoxide symptoms over an eight year period in her small, rented home. She believed the source was her hot water heater which had been replaced three times. History showed first heater was replaced due to a water leak. Second heater was replaced because gas company red-tagged it due to its flame being improper and it was found to be a propane heater using natural gas. Third heater was found to be O.K. Inspection found room was too small, room had no combustions air openings, flue cap was incorrect type, flue cap was too low. Test showed carbon monoxide build-up when fired. Case settled favorably for victim.
Client: Shane & Taitz of Greenbrae, California
Side: Plaintiff. 2010
Case: Woman experienced brain damage from non-maintained floor furnace. Found bottom of flue missing. Found flue from furnace to outdoors rotted through and resting on crawl space ground. Found heater controls misbehaving.
Side: Plaintiff. 2007
Case: Young woman died of carbon monoxide in her sleep in an apartment building in LaHabra, California. Natural-gas fired wall heater was found to have been improperly assembled during amateur repair. Consequently, carbon monoxide was created and not vented. The only interesting aspect of this investigation is that no harm had manifested earlier
Client: Sempra Energy Law Dept. (for Southern California Gas)
Side: Defense. . 2007.
Case: Entire family of about 8 people was poisoned in their up-scale Manhattan Beach home by their Laars & Jandy Model EHE350NB pool heater. The problem was identical to that which caused the death described in the following case. I had warned Jandy Pool Products of this defect in their product almost a year earlier. The “fix” needed is utterly simple, yet Jandy has done nothing.
Client: Jean Paul Wardy (victim) of Center Call Properties, El Segundo, Calif.
Side: Plaintiff. 2007.
Case: Young woman was injured by carbon monoxide while living in a very small (256 sf) cottage. Questions was, “Which was the source: Hot water heater in a small enclosure having no combustion air vents? or a gas range pilot light having a CO measurement of 135 ppm 3 feet above the flame?” P.G. & E. measured CO both at the stove and in the water heater enclosure. Then the structure and components were destroyed before I was engaged. My modeling calculations showed that either source could have been responsible.
Client: Paul Van Der Walde of Sunnyvale, Ca.
Side: Plaintiff 2007
Case: Furnace in single story ranch home created heavy carbon monoxide which entered home, causing severe brain damage to 5-year old boy.
Results of Investigation: Two causes were found. First, faulty gas valve in furnace allowed gas pressure to be un-regulated, resulting in over-firing and consequent creation of carbon monoxide. Second, a defect in flue located within blower suction compartment of Amana Model GC1C090CX50 downflow furnace allowed carbon monoxide to enter home. Problem with White-Rodgers Model 36E22-203 gas valve was found to have improper factory-installed springs which led to a tendency to hang up wide open.
Client: Beyer, Pongratz & Rosen of Sacramento, attn: Erik Child, Esq.
Side: Plaintiff. 2004
See Mr. Liston’s web site for more examples.
Here are more case studies by Thomas H. Greiner, Ph.D., P.E., Associate Professor, Iowa State University Extension Housing Engineer
The point is, the heat exchanger (good or bad) does NOT determine your safety!