CO alarm contamination
Posted 02-05-2016 at 05:29 AM by ladagobago
Carbon Monoxide detectors that many RV owners purchase are common electro-chemical sensors found in most big box stores and in fact most any hardware outlet. These products claim long life, ( some up to 10 years) but are not able to be tested and are susceptible to outside contaminates. What most folks don’t know is what is inside these devices which in reality is a miniature chemical laboratory complete with reactant chemicals, electricity and electrodes.
Substance-specific (gases) electro-chemical sensors are available for many of the most common toxic gases including hydrogen sulfide, carbon monoxide, sulfur dioxide, chlorine, chlorine dioxide, ammonia, phosphine, ethylene oxide, nitrogen dioxide, ozone and others. “EC” sensors are compact, operate on very little power, have excellent linearity and repeatability, and generally have a long life span 6-10 years. The detection technique is very straightforward in concept. Gas that enters the sensor undergoes an electro-chemical reaction that alters the electrical output of the sensor and the electrical output is proportional to the amount of gas present. EC sensors are usually minimize the effects of interfering contaminants with pre-filters, making the readings as specific as possible for the gas being measured. The one caveat to this is that combination smoke and CO detectors have a different set of filters to allow wider spectrum of gasses for the smoke side of the system. This allows easier entry of contaminate elements into the EC chamber.
The internal organic vapor filter included in most CO sensors reduces the effects of interfering contaminants, however, once the filter is saturated, these contaminates can enter. Once that occurs the CO sensing electrode reacts to a wide variety of interfering contaminants including alcohols, (such as methanol and isopropyl alcohol), solvent vapors, (such as toluene and MEK), combustible liquids, (such as kerosene and jet fuel), and unsaturated hydrocarbon gases (such as ethylene, propylene and isobutylene). Many CO sensors also show a significant response to nitric oxide, (NO). CO sensors also respond strongly to acetylene gas (found in propane). Since the internal filter does not absorb acetylene, the sensor shows a very strong and immediate response to this gas.
Unfortunately, although CO sensors recover rapidly from exposure to hydrogen found in the off gassing of batteries, it can take hours or even days for the sensor to recover completely after exposure to solvent vapor or acetylene. Although CO sensors are not usually harmed by exposure to daily minimal concentrations, exposure to very high concentrations of solvents or alcohol vapor can permanently damage the sensor. Never use alcohol or solvents to clean the instrument housing or sensor compartment area! Sample draw tubing or filters that are contaminated by solvent or exposure to heavy fuels (such as diesel vapor) should be discarded and replaced. There are many house hold cleaning sprays (Windex as an example) and cosmetic sprays which also contain contaminate gasses and chemicals which may affect a CO. Since there is no consumer method to test the quality of the element, expecting a CO detector to last for 10 years in an RV is questionable. The test buttons only test the annunciation circuit. We use Solo C6 gas to test our systems.
Substance-specific (gases) electro-chemical sensors are available for many of the most common toxic gases including hydrogen sulfide, carbon monoxide, sulfur dioxide, chlorine, chlorine dioxide, ammonia, phosphine, ethylene oxide, nitrogen dioxide, ozone and others. “EC” sensors are compact, operate on very little power, have excellent linearity and repeatability, and generally have a long life span 6-10 years. The detection technique is very straightforward in concept. Gas that enters the sensor undergoes an electro-chemical reaction that alters the electrical output of the sensor and the electrical output is proportional to the amount of gas present. EC sensors are usually minimize the effects of interfering contaminants with pre-filters, making the readings as specific as possible for the gas being measured. The one caveat to this is that combination smoke and CO detectors have a different set of filters to allow wider spectrum of gasses for the smoke side of the system. This allows easier entry of contaminate elements into the EC chamber.
The internal organic vapor filter included in most CO sensors reduces the effects of interfering contaminants, however, once the filter is saturated, these contaminates can enter. Once that occurs the CO sensing electrode reacts to a wide variety of interfering contaminants including alcohols, (such as methanol and isopropyl alcohol), solvent vapors, (such as toluene and MEK), combustible liquids, (such as kerosene and jet fuel), and unsaturated hydrocarbon gases (such as ethylene, propylene and isobutylene). Many CO sensors also show a significant response to nitric oxide, (NO). CO sensors also respond strongly to acetylene gas (found in propane). Since the internal filter does not absorb acetylene, the sensor shows a very strong and immediate response to this gas.
Unfortunately, although CO sensors recover rapidly from exposure to hydrogen found in the off gassing of batteries, it can take hours or even days for the sensor to recover completely after exposure to solvent vapor or acetylene. Although CO sensors are not usually harmed by exposure to daily minimal concentrations, exposure to very high concentrations of solvents or alcohol vapor can permanently damage the sensor. Never use alcohol or solvents to clean the instrument housing or sensor compartment area! Sample draw tubing or filters that are contaminated by solvent or exposure to heavy fuels (such as diesel vapor) should be discarded and replaced. There are many house hold cleaning sprays (Windex as an example) and cosmetic sprays which also contain contaminate gasses and chemicals which may affect a CO. Since there is no consumer method to test the quality of the element, expecting a CO detector to last for 10 years in an RV is questionable. The test buttons only test the annunciation circuit. We use Solo C6 gas to test our systems.
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