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How to perform a visual inspection to check for carbon monoxide hazards: this article lists visible carbon monoxide gas hazards in buildings: things that you can see during a visual inspection that mean increased risk of carbon monoxide gas (CO) release and poisoning. This text intends to assist readers in understanding these topics. However it should not be considered complete nor authoritative (no single article is satisfactory); we include additional advice and safety warnings about testing for dangerous carbon monoxide in buildings.
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Guide to Inspecting buildings for Visible Evidence of Conditions Likely to Produce Dangerous Carbon Monoxide Gas
IF YOU SUSPECT CARBON MONOXIDE POISONING GO INTO FRESH AIR IMMEDIATELY and get others out of the building, then call your fire department or emergency services for help. Links on this page also direct the reader to carbon dioxide gas information in a separate document.
Seek prompt advice from your doctor or health/safety experts if you have any reason to be concerned about exposure to toxic gases.
Carbon monoxide poisoning can be fatal but exposure at lower limits can produce flu-like symptoms and headaches that are often mistaken for ordinary illness.
The fact that you cannot see nor smell dangerous carbon monoxide gas does not mean that there is nothing to look for when assessing the safety of heating equipment. Not only are there easily spotted installation errors (the first list below), there may be more subtle but easily visible errors if you know what to look for (the second list below).
Visible building conditions risking increased carbon monoxide hazards
This is by no means the complete list of errors that can cause dangerous carbon monoxide exposure in buildings, but here are some common foul ups outside of the workplace that can cause dangerous levels of indoor carbon monoxide:
Other clues which can suggest a risk of carbon monoxide hazards in buildings
In addition to the installation of CO monitoring alarms in buildings, a variety of electronic and gas sampling equipment is available to make spot checks for hazardous gases. We have and have used a variety of these devices under a wide range of conditions.
Watch out: While a "positive" indication of a gas such as carbon monoxide is an important indicator of a hazard, a "negative" or "not found" result is nothing to rely on.
The fact that dangerous levels of CO are not present in a building at a particular instant is absolutely no guarantee that dangerous levels of CO (for example) may not occur even moments later. For example, opening a window, turning on a fan or clothes dryer, closing a door, and similar innocent acts can significantly change air flow, combustion air, and other building conditions.
Therefore spot tests for dangerous gases should not be relied upon to guarantee building safety. This is why the list of visual inspection items and proper heating equipment maintenance are so important.
Suggestions and content additions are invited. Contact me with items to add to these lists.
Heating System Check Recommended for Carbon Monoxide - CPSC Release 88-92
CHIMNEY INSPECTION GUIDE contains detailed suggestions for inspecting building chimneys including the detection of blocked chimney flues or indications that a chimney may be blocked.
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Many sources I (DF) reviewed indicated that if carbon monoxide exposure was sub acute, that is if the person did not lose consciousness and was removed from the CO exposure before losing consciousness, then any medical effects were temporary. Indeed detection of CO exposure at a hospital is problematic since CO leaves the bloodstream quickly once a person is exposed to normal air. However there is evidence that lasting physical damage may occur from carbon monoxide exposure, though the popular press has not (2006) discussed the exposure level and duration necessary for these effects.
Heart muscle damage occurs from Carbon Monoxide (CO) exposure, screening recommended
31 January 2006 - The New York Times Science Section reports on a new study, released in JAMA's January 25 2006 Magazine Issue, and which indicated that people exposed to carbon monoxide suffer damage to their heart muscles and are at much greater risk for heart attacks in later years.
The Times article asserted that CO Poisoning results in 40,000 emergency visits a year in the United States - the most common accidental poisoning event in the U.S. with an annual average accidental death rate of about 1000 people and average suicidal death rate of about 2400 people. [U.S. CDC] Five percent of such patients die in the hospital. Research was not cited regarding subacute exposures and exposures which do not result in a visit to a hospital. -- New York Times Science Section, January 31, 2006 p. F6, "After Crisis, Carbon Monoxide Still Takes a Toll."
The carbon monoxide exposure and heart muscle damage study was led by Christopher R. Henry, Minneapolis Heart Institute Foundation, in the current [Jan 2006] Journal of the American Medical Association The study examined the medical history of 230 people exposed to carbon monoxide and treated at hospital between 1994 and 2002, following their health to 2005.
After 7 1/2 years, in this otherwise low risk (of heart failure) population, 25% of the originally-surviving patients had died - a rate about three times the average heart failure death rate statistic. For people who had suffered heart muscle damage the mortality rate was 38% with half of the mortalities being (apparently) traced to cardiovascular problems.
The study concludes that people who are exposed to carbon monoxide should be screened for heart muscle damage. Heart muscle damage from CO poisoning (in the study) was characterized by elevated levels of cardiac troponin I (a type of protein) or creatine kinase-MB (a type of enzyme), and/or changes in diagnostic electrocardiogram (ECG). -- DJ Friedman paraphrasing the NY Times article and JAMA's news release regarding this study.
More references for this study:
Carbon monoxide is a colorless, odorless, tasteless gas that, in its effects on humans, is a chemical asphyxiant - that is, it causes asphyxiation, or death by preventing a person from receiving adequate oxygen. When inhaled, carbon monoxide combines with hemoglobin in the blood more readily than oxygen does. Thus CO "displaces" or moves oxygen out from hemoglobin in the bloodstream. This interferes with oxygen transport by the blood.
A person suffering from carbon monoxide (CO) intoxication may first experience euphoria (similar to the effect of a martini or two), then carbon monoxide poisoning effects lead to a headache, followed by nausea and possibly vomiting as the concentration of carboxyhemoglobin in the blood increases.
To prevent these effects, OSHA has established a PEL of 50 ppm for an 8-hr exposure, identical to the TLV. NIOSH, on the other hand, has decided to be more conservative and recommends a standard of 35 ppm. All of these concentrations refer to exposures with durations of 8 hr/day, 40 hr/week for a working lifetime and all are attempts to establish a "no effect" level.
To prevent these effects, OSHA has established a PEL of 50 ppm for an 8-hr exposure, identical to the TLV. NIOSH, on the other hand, has decided to be more conservative and recommends a standard of 35 ppm.
All of these carbon monoxide or other gas exposure limit concentrations refer to exposures with durations of 8 hr/day, 40 hr/week for a working lifetime and all are attempts to establish a "no effect" level. Here are some other exposure levels and effects of carbon monoxide exposure from various sources:
NOTES to the Carbon Monoxide Effects Table: sources include OSHA, EPA, www.transducertech.com
ABBREVIATIONS: used with gas exposure limits:
To convert between % and ppm concentration of substances see CONVERT PPM to % CONCENTRATION
Safety Warnings About Using a Gas Detection Device to Check for Carbon Monoxide in buildings
In general, we should never detect the presence of carbon monoxide or "CO" in buildings beyond a possible brief and insignificant "belch" of gases from the draft hood of some heating appliances during appliance start-up when chimneys and vents are cold. In other words there should never be a continuous release of flue gases nor a stream of even low levels of CO in a building.
Watch out: Testing for any gas in a building by relying solely on test instruments can be dangerously misleading.
False positive gas test results: The TIF8800 or other equipment that can detect CO can detect very low levels of flue gas or combustible gases or carbon monoxide. But instruments such as the TIF 8800 that are not specifically designed for CO will also respond to other substances that are miscible in air.
Dangerous gas detection instruments work best in the hands of a very experienced building investigator and instrument user.
False negative results: any gas detection instrument is vulnerable to variations in building conditions or in the operation of mechanical systems in the building that can temporarily hide the presence of a dangerous gas leak. For example, a leaky heat exchanger in a heating furnace may leak detectable gases into the warm air plenum only until the blower fan comes on. Changes in building pressures, open or shut windows or doors, fans on or off, and other such variables can completely change the detectable presence of a dangerous gas indoors.
Dangerous CO may be mixed with warm flue gases
Similarly, although a gas may be rated as "heavier than air", an inexpert building inspector or hygienist who tests for such gases only "low" in the building could be making a dangerous mistake. Carbon monoxide gas, when produced by a heating appliance, will typically be mixed in with other combustion products and will be released as part of warm or hot flue gases that should be venting up a chimney. Therefore testing even for a heavy gas, if it may be mixed with hot flue gases, needs to include testing high in indoor spaces, not just down by the floor.
For this reason, if you call a fire department or emergency worker to test a building for the presence of a dangerous gas such as flue gases, leaks in natural or LP or propane gas lines or equipment, or carbon monoxide levels, even if the worker detects no gas leak present at the time of the inspection that is not a guarantee that the building is safe.
What should you do about this gas test reliability problem? Where there are reasons to be concerned about unsafe gas levels in a building, a more thorough building investigation is in order. Such an investigation includes at least
Readers should see GAS DETECTOR WARNINGS for additional recommendations.
Original document source
This carbon monoxide discussion file originated from a technical expert message board discussion on Carbon Monoxide and later Carbon Dioxide alarms, featuring comments by one of the leading authorities on CO, Jack Peterson, P.E., CIH, Ph.D., in May, 1987.
NOTE: Daniel Friedman extracted CO and CO2 sections from that document, edited and added practical and field inspection-based information. Since its original publication this document has been expanded by reference materials from a variety of other sources.
Safety Suggestions: Install Carbon Monoxide Detectors in addition to Smoke Detectors
Carbon monoxide detectors are inexpensive and readily available, both as a battery-operated unit and as a unit that plugs into an electrical outlet in the home. No home should be without this safety protection, and homes with gas-fired equipment (natural gas or LP propane), space heaters, or other sources of risk should be extra cautious. Smoke detectors do not protect against carbon monoxide poisoning, and the opposite is also true. Carbon monoxide detectors do not warn of smoke or fire.
Frequently Asked Questions (FAQs) about how to inspect buildings for possible CO or carbon monoxide gas leaks, hazards, poisoning sources
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