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Advice On Carbon Monoxide Alarms

Nov 25 '01 (Updated Nov 30 '07) Write an essay on this topic.

The Bottom Line Carbon Monoxide, (CO), "THE SILENT KILLER", ...Some of what you should know about keeping your home free of CO and not relying on cheap technology to save you.

Carbon monoxide...also known as "CO" and as "The Silent Killer".... Is there anything more frightening than something that we know can hurt or even kill us, but we can't see, smell, touch or taste it? Carbon monoxide (CO) enjoys just such an insidious reputation and the marketing whiz kids, who sell CO detectors, haven't missed an opportunity to cash in on it. It wasn't too many years ago that some Madison Avenue genius came up with; "CO...The Silent Killer". It almost sounds like the title for a new thriller and I'll bet that phrase has helped to sell millions of CO alarms to consumers throughout the world.

Well folks, in the face of government by-laws being passed all over North America, enforcing the installation of CO alarms, the time has come to examine the facts about carbon monoxide and these alarms. I have started to write this piece several times, but it is a difficult subject to dissect. Let's face it, this isn't a sexy subject.

Properties

We can begin by agreeing that if you have a fuel burning appliance you probably have some levels of CO in your home and it is odorless, colorless, tasteless and of course, silent. CO can and does kill people or make them very ill. I can also bet that, of those of you who take the time to read this editorial, 99.9% of you are exposed to some levels of CO each and every day of the week, either in your home, at the office, from buses, cars and trucks on the street and especially in a factory environment with propane fork lift trucks and direct-fired rooftop make-up-air heaters.

For the benefit of those who have never read anything I've written, CO is not a normal by-product of combustion. CO is a product of incomplete combustion in any appliance that uses carbon based fuel, including, but not limited to: natural gas, propane, home heating oil (#2 fuel oil) kerosene, butane, wood, coal, and cigarettes.

You can be exposed to low to moderately high levels of CO in your home. It can be generated fairly easily in, furnaces, boilers, room heaters, water heaters, cook stoves, fireplaces, wood stoves, gas powered refrigerators, gas dryers, grills/barbecues, and cigarettes.

Carbon monoxide is absorbed by the hemoglobin your bloodstream 200 times faster than oxygen. Once CO is absorbed by the hemoglobin in your blood, it can stay in your system for several days and the CO blocks the much needed oxygen from being asborbed. Once high levels of CO have been absored you are suffering from carboxyhemoglobin.
Moderate to high carboxyhemoglobin will take a person through the progressive stages of asphixiation. In simple terms, sufficient levels of CO can suffocate you.

How much CO exposure is too much?

This is something everone should think about and I really don't care how safe you "think" you are from CO exposure. If you don't care about your own health, read on for the sake of those who are too young to read this for themselves.

Measured in parts per million (PPM)you will find that almost every health department at every level has a slightly different view on what is considered safe levels of exposure.

The one I subscribe to, happens to be from a Canadian study on indoor air quality, which is a whole different discussion in itself. However, the following numbers published by Canadian agencies and rounded off for simplicity, seem to be close to the U.S. tolerance guides and other published reports.

"HEALTH IMPACT OF CARBON MONOXIDE"

0 PPM - Desirable level (not much of a surprise there)
9 PPM - Maximum indoor air quality level
50 PPM - Maximum concentration for continuous
exposure over an 8 hour period.
Headaches, tightness in the chest may begin
400 PPM - Frontal headaches within 1-2 hours of
continuous exposure, life threatening after 3
hours.
800 PPM - Nausea, convulsions, comatose and death within
2 hours of continuous exposure.
1,600 PPM - Nausea, convulsions, comatose and death within
1 hour of continuous exposure.
12,800 PPM- Death within 1 to 3 minutes of continuous
exposure.

NOTE: Health effects and times can vary based upon age, sex, weight and overall state of health, children, elderly people and those with pre-existing respiratory health problems are more susceptible to lower levels. Pregnant women and small pets also have higher risk.

CO Alarms

I suppose by now everyone thinks that I am about to promote CO alarms. Well, I'm not.

There are two basic types of CO detectors on the shelves today. One operates using a clear, chemically treated gel that reacts to exposure to CO by darkening and with enough exposure, blocks out a signal to a tiny CAD cell that activates the alarm. These devices are fairly inexpensive. I've seen them priced from $19 to $50.00 from a dozen different manufacturers.

PROBLEM 1: They rarely, if ever, tell you that they have a shelf life. The chemically treated gel may already be near the end of it's usefulness by the time you buy it at your favorite hardware store.

PROBLEM 2: They're cheap. No, I did not mean to say inexpensive, I meant to say cheap. Not only is their usefulness over a few years questionable, their alarm settings are questionable.

The other type uses an electronic sensor head that is theoretically calibrated to sense dangerous levels of CO in your home. It draws it's power from either batteries or is plugged into your wall socket. Some can even be hard wired into your home.

PROBLEM 3: The all important sensor head "will" burn out within one to five years. Something that none, that I've seen on the shelves, advertise to the buying public. Some offer a warranty on the sensors and offer replacement sensors, but at one major distributor of these things, the clerk didn't even know that and they weren't in stock. I couldn't even find out how much they cost.

PROBLEM 4: Their calibrated alarm settings, which begin at 70 PPM (note above chart) are supposed to be set for levels that will protect you from over-exposure to CO, are not consistent after one, two or three years of operation. Independent studies found their settings wander from lower than factory settings, giving false alarms, to higher than factory settings, giving you no alarm. Neither is acceptable in my opinion.

PROBLEM 5: With regards to the models that plug into your electrical sockets. Since, CO is going to be coming into the home with hot flue gases, it is going to rise like a hot air balloon. CO will fill the upper levels of the home or the room they are contained in, slowly filling the room from the ceiling down to the floor level where your wall sockets are located. By then, it may be too late.

Hard wired units high on the wall or on the ceiling are best. In the case of a gas fireplace, in the same room, not too close to the fireplace or too close to a window. If the house is open to upstairs bedrooms another up on the ceiling above bedroom doors is a good idea.

Even though I have a major problem with the lack of credibility these products have for sensing in time and working for a reasonable period of time after installation, I still think you should invest in a couple. Some protection is better than none.

I also think any room that has a gas appliance in it and for reasons noted above, not plugged into an electrical outlet near the floor, but up near the ceiling in the furnace room or the utility room with the gas or oil fired water heater.

Of course the packaging on these gizmos scream out about the benefits of having one, two or a dozen of them installed in your home, but, no where, on that packaging did I find warnings about their diminishing capacity to work over time. Why am I not surprised.

They also don't like to be reminded that only a few short years ago over 1 million of them had to be recalled.

My concern about inexpensive technology that is intended to save lives is due to having once owned a really good, top of the line, infra-red combustion analzyer, specically designed and programmed for measuring carbon monoxide emissions, on scales ranging from 0-100 ppm, 0-500 ppm to up to 0-5000 ppm. (Beyond, 5000 ppm, I don't want to be anywhere near there.) I had purchased it about 15 years ago and brand new, it cost over $4,000.00. When it was properly calibrated, with a specially ordered calibration gas containing a known quantity of carbon monoxide, it was an amazingly accurate device. In my work, testing new gas and oil appliances I could measure the affect of every modification and track changes in combustion performance over time.

What's the point? My amazingly accurate ($4,000.00) CO analyzer had to be recalibrated every day. As all CO analyzers do. Using a bottle of inert gas (nitrogen) to clear it (zero gas) and a cylinder of calibrated CO gas. Otherwise the reading would "wander" and I would receive incorrect data, either low or high of the actual levels.

Quite simply, if my ultra expensive, laboratory grade combustion analyzer needed so much service to keep it accurate, just how much faith should I put into a device that retails for anywhere from $19.00 to $100.00?

These products are listed by Nationally recognized laboratories. However, Underwriter's Laboratories Inc. (ULI), the Canadian Standards Association (CSA), Underwriter's Laboratories of Canada (ULC)do not certify that products will work, in every case. Their job is to ensure that these products are safe and meet the standards set for them. Unfortunately, their limits of liability stop at the lab door. The manufacturers are liable for the production and functionality of the product.

Now let me throw a curve ball at you. I don't think anyone who buys a CO alarm is crazy. I personally don't have one in my home and I wouldn't buy one, but that's me.
They're highly recommended by local politicians, gas utilities, fire departments and equipment manufacturers. Sadly, I think the politicians recommend them for political reasons and the rest recommend them because there are going to be a few that work and do the job they were designed to do. On that basis, a few lives saved by a CO detector, out of the millions sold (that become wall ornaments) make them something that have some redeeming value. Some recommend them without knowing the technical reliability of them.

Why don't I have one? I check my gas appliances regularly for performance. I look for signs of problems with them and I've studied the construction of my home and I have natural air infiltration.

What can you do to keep the air in your home safe and healthy? Don't buy an unvented gas fireplace or heater. (Okay, I won't go there again. :-)

Find a service company in your area that owns a combustion analyzer. Most good companies, these day, own at least one or two portable analyzers. Ask them if they have a competent service technician who can come out to clean and service every fuel burning appliance in the home and run a combustion analysis on them all. Ask for a copy of the results. You will want to know what the CO and CO2 (carbon dioxide) levels are within the exhaust of each appliance, after it has been operating for fifteen minutes, from a cold start. Carbon dioxide *(CO2) is a normal by-product of combustion and is read in percent. An extremely low CO2 reading (1-2%) may indicate poor efficiency, or too much dilution air. A mid range diluted CO2 reading in your vent is normal with most heating appliances depending on design, age, venting configuration (2-5%). A higher reading from 5 to 7% diluted in the vent isn't too uncommon with newer gas appliances. However, a reading higher than that of 8 to 11% is usually an indication of a combustion problem, insufficient secondary air or dilution air, or over firing the input rate of the appliance, or blockages in the flue gas passages within the appliance and is often accompanied by high CO readings.

On an appliance with a circulation fan, the combustion test should be done with the fan off and then rechecked with the fan on. A crack in the heat exchanger or the firebox may not be evident and discovered until the fan comes on.

Have them check the ambient air throughout the home as well, with all of your usual gas appliances running. Check for CO or CO2 in the home, the duct system and especially around the outside of the appliances themselves. You will usually get some readings within the kitchen around a gas cook stove. However, there are really no good reasons to pick up CO or CO2 readings in the furnace room or around the face plate of a gas fireplace or heater. Such readings are usually the result of a leak in the system, possibly a bad gasket, that needs to be repaired. Have them locate it, and fix it or in the worse case scenario, (with a cracked heat exchanger or firebox) you may have to have the appliance replaced.

Chances are you will get some CO readings in the vent of the appliance, don't worry as long as it's between 0 and about 50 ppm. A much higher reading may indicate that there is something wrong with the appliance.

While they're at it, have them run performance efficiency tests on each appliance, ask them to tell you in actual percentages what the % of heat loss is up the chimney and how close that reading is to the manufacturer's rating plate on the appliance. Efficiencies are often automatically shown on many combustion analyzers.(Rating plates are required by law on all gas appliances and the difference between the output and the input will give you the certified efficiency rating. These ratings are established by independent testing at certification test labs throughout North America.

If your favorite service technician is a good ole boy, who's been fixin' your appliances for years and he don't cotton to them new fangled contraptions called combustion analyzers, cause, "he kin tell jist by lookin' at the fire how good it is." (I think I've met him a few times.) Have a beer with him on Saturday night and secretly call in a qualified person to do it for you on Monday morning.

Personally, I don't try to make my house a sealed envelope. I enjoy a bit of fresh air, just a bit mind you. So don't be sealing up every little crack around doors and windows, we weren't meant to live in hermetically sealed homes. Seriously, I don't seal up all of the gaps around windows and doors. It may cost a few dollars more to heat my home each year, but, a certain amount of natural infiltration air is healthy for the inside environment.

Those of you who want to live in a vacuum,... don't. You should really invest in an air to air heat exchanger, to maintain a constant number of air changes per hour (ACH). That guy you hired to test your gas appliances for you is probably skilled enough to recommend the right unit size and number of air changes per hour (ACH's) your home needs.

If you're lucky enough to live in a drafty old home, like the one Grandpa and Grandma lived in, there's a good chance you won't have a major problem with ACH's. Enjoy it in good health the way they did and live to a ripe old age.

I suppose I could have saved you a bunch of time today if I had simply wrote these last few paragraphs in the beginning, but then, you wouldn't have read the rest. Look at what you would have missed!

Imagine this is a few weeks from now and you've followed my advice.

1. All of your appliances are performing according to the manufacturer's specifications, clean and as efficient as they can be, for their age. You have a current analysis that says they are running safe. IMPORTANT

2. You know your home is getting an ongoing adequate amount of fresh air and that there are no traces of harmful CO throughout the house.

3. Sure it cost you a few bucks, for the service call, but, you're feeling good about your home and you've made a commitment to have that guy you found with the analyzer come back again next fall to do it all again.

Do you still want to run out and spend some money on a CO detector? If it makes "you" feel better, go for it.
First, don't just buy the most expensive one, check out the Consumer Reports on these things that have been printed and updated annually for three or four years. The last report I read was not very encouraging for one specific reason. There were still reports of units not functioning at all after one year of operation and even Consumer Reports methods of testing was questionable, clinical test methodology for this type of product. That's a whole other issue and I hope to get to it soon.

If you have any questions that I haven't answered here please feel free to drop me a line and I'll do my best to help you. Either leave a comment here or write to me at, the_gas_man@hotmail.com

I hope this effort has proven informative for you. Thanks for reading.

Regards,
The Gasman

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