Cracks Rarely Cause Carbon Monoxide, But Require the Most Time to Identify
Because heating service people have been trained to inspect heat exchangers for minor cracks, they
spend the majority of their service time in your home doing just that -- looking for cracks. Unfortunately, they
really haven't been trained to survey the entire home and find out how it is operated and to determine whether
there is adequate combustion air and whether fresh-air intakes are required.
Basically, they walk past the potentially fatal problems with combustion air and flues to look for
heat exchanger cracks that rarely affect the indoor environment.
If you have a typical, residential 65% to 80% AFUE, forced-air gas furnace with an air-conditioning
coil and duct work attached to it, then carbon monoxide from a heat exchanger crack is NOT going to occur. At least
in 99% of the cases.
There's always an outside chance that an odd-ball installation creates a problem. If you have an
old gravity-furnace, or floor furnace or duct-furnace with a propeller fan, or a suspended unit heater, then it's a
different story. Even old Williamson and AFCO furnaces could dribble carbon monoxide into the home if there was no
a/c coil on the furnace and the duct work was oversized.
However, furnaces equipped with air-conditioning coils and duct work attached don't bleed carbon
monoxide from the fire-side of the heat exchanger to the indoor-airstream (through a hole or crack.) The indoor
blower creates too much air pressure inside the furnace cabinet. Any time there's a hole or crack, air moves from
the blower air stream, through the crack, INTO the heat exchanger. It's never the other way around.
Somehow safety issues have
turned a simple
problem into a rushed, selling situation
and a FORCED furnace replacement.
At the same time, the real
the kind that causes death and injury,
are being ignored.
Somehow, it seems like the HVAC industry has ignored the fact that modern furnaces don't operate the same way the
original coal and gas-fired gravity furnaces did. When those early furnace had a breach in their heat exchangers,
carbon monoxide, flue gas and soot were definite problems.
That changed when more compact furnaces were developed with integral blowers and air-conditioning.
Unfortunately, the testing agencies and "authorities having jurisdiction" felt it would be safer to simply require
ANY heat exchanger with a defect be replaced.
Almost every natural gas utility has mandated (made it
part of their policy) that gas furnaces be replaced (or their heat exchangers replaced) if a hole or crack is
detected, no mater how small. Consequently, service companies make furnace heat exchanger checks their high
priority when performing routine maintenance or repairs.
Many local ordinances require you to have the gas utility "inspect" your gas furnace
to insure it operates safely and the heat exchanger is intact before a change in property ownership can take
In fact, if you are trying to sell your home, this is one area where you can
not negotiate with a potential buyer. You are REQUIRED to replace the furnace (or heat
exchanger) before the sale can proceed.
This situation may appear to be OK from a safety standpoint, but consider the
The reason heat exchangers appear to be critical to safety is because of a
misguided belief that a crack or hole in a heat exchanger will allow carbon
monoxide to enter a home. For standard efficiency, 80% AFUE or less furnaces, this is a myth.
The fear of carbon monoxide from a simple heat exchanger crack is a hold over from the
"old" days of "gravity furnaces" with pot-belly (round) heat exchangers. These furnaces might be coal-fired,
oil-fired or gas fired. In many cases they were upgraded with gas conversion burners or in-shot burners (circa 1950's.) Splits in those
heat exchangers caused problems with carbon monoxide entering the home. The coal-fired and oil-fired
burners produced plenty of other unsavory gasses besides carbon monoxide so it was usually easy for
an occupant to tell that something "bad" was in the air. They could smell it or it would make their
eyes water. With gas conversion burners, very little odor was emitted which made it hard for folks
to know that their heat exchanger had split open. In fact, gas
conversion burners had the ability to "push" the products of combustion into a home' s air stream
and could sometimes produce high levels of carbon monoxide.
Gas furnaces with heat exchangers made in the last 20 to 30 years do NOT emit carbon
monoxide just because of a crack or hole. If a furnace is generating high levels of CO, there are other
problems that need to be identified and solved. When you see diagrams where they've circled a
little hairline crack and are calling it dangerous ... well let's just say
that's what they may have been taught, but it is not the facts.
Visual heat exchanger checks are questionable at best. Short of
dismantling the furnace, there is NO definitive way to guarantee that a heat exchanger does NOT have a
crack or hole. In many heat exchangers, it's almost impossible, even with a remote camera, to inspect
all surfaces for cracks.
One of the better detection methods currently being used is a lighted remote
camera (camera on a stick) with a water sprayer. They spray water on one side of the heat exchanger and
use the camera to see wet cracks on the other side. But even this method is not a 100% guarantee that
the heat exchanger is intact.
- Here's the important point: the conditions that lead to carbon monoxide poisoning are usually
ignored because mechanics are focused on gas appliances, specifically heat exchangers, as the
likely culprits. Consequently the home is never checked to insure it can safely support the gas appliances
(combustion air and properly sized flue.) The home owner is never cautioned about using their attic fan or how
the furnace flue and operating other devices (like a Jenn-Air or kitchen exhaust hood) can cause carbon
monoxide problems. They also fail to highlight how the home's construction can have a big impact on carbon
monoxide safety. (This is the point of this web site and the report Carbon Monoxide Myths.)
Fear of CO is the Easy Way to make a Sale
Here's the fastest way to make a furnace sale - perform a heat exchanger check while
doing routine maintenance or repairs. (Most service companies and gas utility providers
mandate that heat exchanger checks be performed whenever a furnace is serviced.)
If there's a "crack" in the heat exchanger, a sale of some sort is almost
guaranteed. In effect, the $49.00 furnace "clean and check" becomes a potential $3,000 furnace installation. (The
cheaper the "clean and check", the more likely it is that your furnace will have a problem.) In fact, there are
outfits that make a good profit teaching companies how to find heat exchanger cracks - and tout their classes as
"replacement sales generators".
With all the publicity about carbon monoxide and heat exchangers, the customer's
anxiety level will be high enough that they won't be asking many questions. They will not be in a position to get
competitive bids which makes the sale a fairly easy task.
To be fair, you should understand that local ordinances and the AGA "require" that furnaces with a
heat exchanger crack or other safety problem be "red tagged" and shut down. Most natural gas providers also require a red tag when a cracked
heat exchanger is discovered. Most HVAC schools teach students that a heat exchanger crack is a severe safety
issue requiring that the equipment be taken out of service. In other words, heating contractors think they must
red tag the furnace if it has a bad heat exchanger.
The gas utilities promote heat exchanger checks and are happy to see new, more
efficient gas furnaces being installed.
Why Holes Are Profitable
Needless to say, the smallest hole in
a heat exchanger becomes a sales oppor-tunity once a service
technician spots it. In many cases, they spend more time looking for the little hole or crack, than they do
inspecting the rest of the furnace, electrical system and flue.
The bottom line is that you are at the mercy of the technician looking at your
equipment. If you deal with reputable service companies that employ people who are honest, you'll be OK.
Going for the "cheapest" rate when selecting a service company could prove to be a
lot more expensive in the long run. Ask around, check with your friends and neighbors. Use Angie's List and check with your local BBB (Better Business Bureau.)
Like it or not, service people in many organizations receive rewards or monetary
incentives based on the dollar volume they generate or their equipment sales. So, while you are thinking that
there's no reason for a service mechanic to mis-inform you, there may be a very good reason to "shade" the truth -
I'm not saying all mechanics worry more about incentives versus what's right for the
customer. Most mechanics are conscientious, honest, hard working people. But, between the inducements to sell
equipment and the misinformation about carbon monoxide, there are a lot of furnaces being prematurely replaced due
to questionable diagnostics.
Myths Make for Easier Sales
This is just one of a number of "myths" circulating
in the HVAC industry. This kind of myth stops the customer from asking too many questions. It lets the companies in
the HVAC business slip out from under potential liability by simply "condemning" equipment based on some vague
notion that it is un-safe to operate. With everyone's fear of carbon monoxide and cracked heat exchangers, no one
really questions the practice.
And the Media Doesn't Help
The myths have been reinforced by repeated exposure in the media, volumes of news
articles, consumer protection information and even utility company policies. It does not matter whether the myths
are true or false. Every contractor, code enforement and safety organization operates as if they are true, so they
must be true. Right?
They are WRONG about thousands of CO Deaths!
Another myth that's perpetuated by
the media and government agencies is the number of deaths caused by carbon monoxide poisoning each year. Some
sources declare that "hundreds" are killed each year. Other media outlets use headlines like "Thousands Die Each
Year Due To Carbon Monoxide." Well guess what ... they are wrong, totally wrong! Nobody checks their facts! They
simply reprint what other agencies have published.
According to the Consumer Products
Safety Commission, which has been tracking carbon monoxide related incidents for the last two decades, fatalities
caused by carbon monoxide poisoning averages a whole lot less than what the media report! (It's actually less than
100 people per year for gas furnaces.) I've got the numbers, straight from the CDC, to prove
(Opens in a new window)
Don't They Care If You Are Left In the Cold?
I've stood in service meetings and posed this
question to mechanics;
"If it's the middle of winter with 20 degree
temperatures and you checked a furnace and found a small hole or crack in a heat exchanger that was NOT creating
carbon monoxide (CO), would you red-tag the furnace?"
Every mechanic, without
exception, said yes, the red-tag was warranted and they would shut down the
Then I asked, "What about the family and the water
lines in the house? The shut-down will cause a lot of inconvenience and may cause damage to their property if the
water lines freeze." There was usually silence. Then some wise guy would always pipe up with "we have to shut it
down because of liability." (In the back of the room you can see the company owners shaking their heads in
Here's the Big Problem
Nobody asked the question;
"Is the crack or hole causing a combustion problem?"
If there is no major flame disturbance or rollout or other operating
problems, then the furnace is probably safe to operate on a temporary basis. It may have been operating for
years with the hole or crack exactly like it is.
Come on - where is common sense?
How about a little compassion?
In the dead of winter we force a family out of their home, leave them
open to potential damage because of water line freeze ups and use "liability" and "danger" and "the rules" as the
Did the mechanic at least use a CO meter to test the furnace to
see if it was producing a high level of carbon monoxide before they shut down the heat?
It Has Been Happening for Years, Now Everyone Believes
This find-and-condemn concept is so ingrained in
the fabric of the business that I have had mechanics not believe their own eyes and test equipment when I tried to
explain what was really happening inside the furnace.
The concern for liability issues loom large and are
responsible for many of the policies adopted by code enforement, gas utility companies and HVAC
I don't mean to imply that all furnaces with heat exchanger
cracks or holes are OK to operate - even temporarily. Some should be shut down and red
tagged. Any system with a large flame disturbance, flame rollout, concusive ignition or
evidence of overheated wiring or components should be turned off and disconnected.
However, the majority of furnaces with heat exchanger cracks will
operate for years without incident. Why throw a family out of their home
by condemning their equipment in the middle of winter when there is no
clear safety issue?
In the end, the consumer feels the pain with
premature equipment replacement, mis-diagnosed combustion problems and a lot of needless
Homeowners need to know what is safe to operate,
and what should be avoided. Most homeowners have the power to minimize their risk from carbon monoxide poisoning
once they understand what to look for. But, without the knowledge, it's easy to fall prey to quick solutions and
How Does This Affect You?
If you have a gas fired appliance, like a gas
stove, or a gas water heater, or a gas clothes dryer, you are affected.
You need to be aware of what dangers your
appliances can pose and what you can do about them.
Misrepresenting CO issues is done by "omission."
There are NO direct efforts or conspiracies by any
government agencies or safety organizations to misinform the public. It's a case of only presenting part of the
information, and is very similar to using a statement out of context. If you never find out the full story, you
assume the information you've received is accurate. This is also how many of the myths about carbon monoxide
I'm here to tell you that what you've been
hearing about carbon monoxide issues is NOT accurate. You've only been hearing part of the
What Can You Do to Protect Yourself?
First, become aware of the
potential dangers and acquire a basic understanding of how carbon monoxide is formed and how your gas-fired
equipment should operate.
Second, Read Gus' letter.
Third, survey your home and
equipment to make sure you haven't been living with a hidden time-bomb.
Fourth, get familiar with the 12 myths.
Fifth, get an industrial carbon monoxide monitor, not a residential CO
This is not a cheap residential carbon monoxide
Those units won't alarm if it senses low CO concentration and most do
not provide an accurate read out of existing carbon monoxide levels.
This is a heavy-duty, accurate, portable, low-level monitor that has a 2-year CR123A battery , is
waterproof and gives a direct read out of current co levels. It has audible and visual alarms that are factory set
at 35 and 200 ppm. It also has circuitry that compensates for humidity which means it remains accurate over a wide
range of weather conditions. Standard co detectors are notoriously inaccurate under low humidty conditions (in the
middle of winter.)
You can use this monitor to check co levels
in any area in your home and then set it on your night stand for protection while you
sleep. Note that the two year battery life is based on 24 hour operation, but very few and short duration
Because this is a low level alarm, you will be able
to protect younger kids and new borns from carbon monoxide levels that won't set off a standard carbon
monoxide detector. Chronic low level carbon monoxide exposure (under 30 ppm) has been shown to aggravate
respiratory problems and may also interfere with cognitive development. It can also cause problems
for older adults with respiratory difficulties or congestive heart failure.