Install, Check, Replace Your Carbon Monoxide (CO) Detectors… Right Now! 13

I’d been planning to write a post about carbon monoxide (CO) detectors for some time now, ever since I installed one not long ago while replacing my first water heater here at the house. I wasn’t in any rush. I’d get around to it eventually.

But a pair of recent and shockingly sad occurrences have forced this project to the top of my DIY list — and to the top of my “must blog about this now” list.

The first story was reported in the February 25, 2014 Idaho State Journal. The headline read: “Four family members found deceased in Pocatello home; carbon monoxide suspected.” The family had two of their grown children away from home serving full-time missions for their church (like the one I did from 1990-1992 in France), who were forced to come home early to face this tragic loss. This single sentence in the middle of the article made my heart sink:

“There was no carbon monoxide detector in the Parrish home.”

The second story is a bit more recent… and hits a bit closer to home. This obituary reports that on March 6, 2014, 45 year-old Christopher Joel Starkey “passed away unexpectedly.” What wasn’t reported in the news or the obituary, however, is the cause of his tragic and unexpected death: carbon monoxide poisoning. He was cooking on a fuel-burning stove inside a building that didn’t have sufficient ventilation. How do I know this? Because as a divorced dad, when my daughters aren’t living with me, they live with their mom in Mapleton, Utah… two houses down the street from the Starkeys. I’d met Chris. His outgoing wife Julie was my oldest daughter’s church group leader. My kids went to school, and to church, with his kids. Chris was an Eagle Scout, an accomplished outdoorsman, served a full-time mission for his church, went to BYU, loved the Seattle Seahawks, and was a tech entrepreneur with computers and networks. All of those attributes describe me… which maybe explains why (even though I had only met Chris a few times) the tragic news of his untimely death caused me to go immediately to and order nine CO sensors; six for the Seattle house, and three for the Utah house.

So the goal of this DIY blog post is to share with my readers what I’ve learned in my research of CO poisoning and CO sensors. If it can help make even one fewer story like the two mentioned above, I’ll sleep better at night knowing I did my best to spread the word.

What is Carbon Monoxide?

Carbon Monoxide (abbreviated as “CO”) is a gas. It’s made up of one atom of carbon and one (mono) atom of oxygen (oxide). It has no color, no odor, and no taste. Carbon monoxide is formed as a byproduct when fuel is burned in an enclosed space and when there’s not enough oxygen available to create carbon dioxide (CO2).

Common sources of CO include combustion engines (like your car), water heaters, lanterns, burning charcoal and wood, and all gas-powered appliances like ranges, furnaces, dryers, or fireplaces.

What is Carbon Monoxide Poisoning?

According to the CDC, CO poisoning occurs because “red blood cells pick up CO quicker than they pick up oxygen. If there is a lot of CO in the air, the body may replace oxygen in blood with CO. This blocks oxygen from getting into the body, which can damage tissues and result in death. CO can also combine with proteins in tissues, destroying the tissues and causing injury and death.” The CDC reports that over 20,000 Americans visit an emergency room every year from CO poisoning. Over 4,000 of them are hospitalized. And worst of all, over 400 Americans die from CO poisoning every year. And in nearly every case, no CO detector was present. The CDC’s Carbon Monoxide Poisoning FAQ has a lot of additional information about the causes and prevention of CO poisoning. It’s worth checking out.

But my goal for this post is to convince you to immediately determine whether you need to install, check, or replace CO sensors in your home. And if you do, to immediately do so. No tomorrow, not next week, but the second you finish reading this post.

CO Sensors

Carbon Monoxide sensors can be found at any hardware store, home improvement center, or major online retailers like They are easy to find, easy to install, and not expensive. You have no excuse for not having them in your home.

My preferred CO sensor the First Alert CO615.

First Alert CO615 Carbon Monoxide Detector

First Alert CO615 Carbon Monoxide Detector

This unit can plug directly into a wall outlet, or can be mounted higher on a wall with included hardware and plugged in with the included long cord. It uses two AA batteries (provided) for backup power and has a digital display for easy visibility of battery life and sensor function. You can press the “Peak Level” button on the front of the unit and it will display the highest level of CO it’s detected in the previous 24 hours, even if the levels didn’t reach high enough to sound the alarm. And even though I consider it one of the “higher-end” consumer CO sensor alarms, it only costs $30 online (shipping included).

You can also buy “combo”detectors that combine smoke detection with CO detection, ranging from this $31 Kidde KN-COSM-BA Battery-Operated CO and Smoke Detector (with talking alarm) to this hi-tech Smoke and Carbon Monoxide Sensor from Nest for $129.

At first thought, you might think a combo unit is the way to go. If you’ll allow me, I’d like to talk you out of that notion. CO detectors have a much shorter service life than smoke detectors (50% shorter on average), so my preference is to split CO detection and smoke detection into two separate devices, and then replace each unit individually when its service life is over.

Smoke detector manufacturers recommend that you replace their units every 10 years (although most experts note that it’s the manufacturers who have an interest in you buying more smoke detectors who suggest that… and that smoke detectors will likely function just fine for much longer).

The first CO detectors to hit the market only had a life-span of 2 years, through some of the most recent models advertise up to 7 years of service life. Keep in mind these recommendations are not based on battery life, but on the life of the sensor itself. My research shows that on average, industry experts have determined that the CO sensors lose their ability to sense carbon monoxide gas after an average of 5 years, and should therefore be replaced every 5 years. Based on that, I have replacement of CO detectors scheduled in my home maintenance calendar at 5 year intervals. I’m scheduling the replacement of the single hard-wired version I use at 7 years, since it states on the box that it’s indicated to reach “End-of-Life” 7 years after it’s installed:

The Macurco CM-E1 box says the unit reaches "end of life" after 7 years.

The Macurco CM-E1 box says the unit reaches “end of life” after 7 years.

Where to Install CO Sensors

There’s some minor debate as to the most effective placement of a CO sensor. Because CO is slightly heavier than air, some experts recommend that sensors be installed on a wall, about a foot or two above the ground (outlet height, conveniently enough). Others suggest that CO from an exhaust will be warm, it will therefore rise and be best detected by a ceiling-mounted unit. The prevailing opinion seems to be that either location is effective for CO detection, as long as the detector isn’t installed in a corner where air will be stagnant. At my house, I’ve installed all the CO sensors at outlet height or higher.

As for the best room(s) in your house for CO detector installation, don’t put one where it’s normal to expect a small or temporary amount of CO to exist… such as inside your garage. If you installed one there, the CO sensor alarm would sound every time you start your car!

Instead, place a CO sensor in or near every sleeping area in your house, as well as in “common areas” of your house where carbon monoxide from a poorly ventilated device could potentially collect and be dangerous, like a living room with a gas or wood-burning fireplace or stove, the laundry room if you have a gas dryer, a furnace room, or the kitchen with a gas range.

I installed a detector in the utility room near one of my water heaters — but not right above the water heater where it might falsely alarm, but next to it, like this:

First Alert CO Monitor and Alarm

First Alert CO Monitor and Alarm

We have three gas fireplaces in our Seattle house: one in the living room, one in the family room, and one in the master bedroom. So I installed a CO monitor in each location. I also installed one in the hallway outside the laundry room, which is the hallway that connects three bedrooms upstairs.

Hard-Wired CO Detectors and Alarm Systems

Before I truly considered the dangers of CO poisoning as a result of the above news stories, I had convince myself that the Macuro CM-14A hard-wired CO detector, which the builder had installed in the basement utility room… and which was wired as a separate zone in our DSC whole-house alarm system, was sufficient.

Macuro CM-14A Carbon Monoxide Detector

Macuro CM-14A Carbon Monoxide Detector

The basement utility room houses two furnaces, as well as the larger of our two water heaters, and is therefore the location in the house with the highest concentration of major fuel-burning appliances. It also shares a hallway with our son’s bedroom.

The hard-wired sensor had been hooked up in 1997, when the house was built and the alarm system originally installed. I didn’t realize, however, that like all CO detectors, the actual sensing unit inside the detector loses its ability to sense carbon monoxide after only a few years, and so I trusted the happy little green LED on the unit that may have been falsely informing me that everything was fine. In reality, that LED maybe have only been informing me that the detector had power, and that the sensor (which had probably already lost its ability to sense) wasn’t sensing anything dangerous. That’s kind of like a bloodhound whose nose has fallen off not barking because he can’t smell anything.

Macurco (now owned by 3M Corporation) no longer makes the CM-14A. They’ve replaced it with the Macurco CM-E1, which costs around $80 online. I considered just throwing another $30 detector into the basement utility room instead, but I liked the idea of having a detector in that room that trip the house alarm and automatically call the fire department , so I coughed up the extra money.

Installing the Macurco CM-E1 in place of the older CM-14A was pretty straightforward. Simply unscrew the old detector from the wall and expose the low voltage wires:

Macurco CM-14A removal

Macurco CM-14A removal

The two red wires coming from the sensor are the 12V power wires, and the blue and orange wires are the relay leads that trip the alarm when the unit senses CO gas. The brown wire sticking out to the left was never connected, and I’m still not sure what its purpose was (the unit’s so old that a web search didn’t produce a manual or wiring diagram). I didn’t have much time to think about it, however, because as soon as I disconnected one of the red power leads, the alarm interpreted that as the relay tripping and triggered the whole-house alarm! Thankfully, I’d phoned the alarm monitoring company a few minutes earlier to ask them to put my system in “test mode.” This is not my first time messing with a monitored alarm. 🙂

The new CM-E1 came with a cute little wiring harness, so I connected the two 12V power and two relay leads to the appropriate wires from the alarm panel:

Macurco CM-E1 wiring harness

Macurco CM-E1 wiring harness

Note the unused green and brown wires on the harness, which I terminated with wire nuts. Unlike the older CM-14A, the newer CM-E1 detector has a trouble relay on-board. The good news is that my alarm panel supports trouble relays — meaning my new sensor could potentially turn on the yellow trouble light on my alarm keypads to alert me if something went wrong with the sensor. The bad news is that whoever installed this sensor originally only ran four-conductor wire from the alarm panel (grrrrrr!). Had they run a full Cat-5 cable (like a real professional would), I could have easily hooked up the trouble relay.

Once all the wires that could be connected were connected, I mounted the new sensor’s wall plate and plugged in the wiring harness to the back of the circuit board:

Macurco CM-E1 wall plate installed

Macurco CM-E1 wall plate installed

The unit beeped and flashed the LED… which the instructions said was the normal start-up procedure. I checked one of the alarm keypads, but it complained that the “Gas Detector” zone was “open” — which isn’t what I wanted to so. Combining that info with the fact that killing the power to the old unit had tripped the alarm, I deduced that the old unit must have been configured in “normally closed” mode, so I set the jumper on the rear of the CM-E1 to “NC,” which fixed the problem.

Jumper switch settings on the back of the Macurco CM-E1

Jumper switch settings on the back of the Macurco CM-E1

With everything reporting properly, I clicked the new unit into place:

Macurco CM-E1 installed

Macurco CM-E1 installed

then held the test button for 5 seconds to trigger the on-board relay. The whole-house alarm sounded again, confirming that if the relay opens (which it’s supposed to do if the sensor detects gas), it will sound the alarm siren and call the fire department.

How to Test a CO Detector (and/or a Smoke Detector)

You might assume that testing a CO detector is as easy as testing a smoke detector. And you’d be right… but not in the way that you think.

When you press the “test” button on a CO detector or a smoke detector, you’re actually only testing the circuitry inside the unit. You’re testing to see if the alarm speaker is capable of making a loud and annoying sound. You’re testing to see if the on-board relay will close (or open) properly and trigger the whole house alarm. You’re testing to see if multiple inter-connected detectors will tell the rest of the detectors around the house to also start beeping. You might even be testing whether the back-up batteries are functional. You’re definitely testing whether or not the test button works. 🙂

But what you’re not testing, however, is whether the sensor inside your unit can actually detect smoke or carbon monoxide… and that’s the most important test of all!

Rather than smoke a cigarette under a smoke detector, or route a hose from your car’s exhaust to your CO detector, there’s an easier way to verify that your smoke and CO detectors can actually do their jobs. For $10, purchase an aerosol can of Smoke Detector Tester Spray (which will last for years) and spray it at your smoke detectors annually when you change the backup batteries (you do change your backup batteries, don’t you?). Also, for $16, pick up a can of Solo C6 Carbon Monoxide Detector Tester so you can test the actual effectiveness of your CO sensors.

Remember, your CO detector’s test button and LED might tell you everything is fine… even if the sensor inside the unit has stopped working. If you want to save some money, split the cost of the test spray cans with a neighbor, then get together once a year to check both house’s smoke and CO detectors. You’ll probably be more likely to test regularly if you have a test buddy.

Final Thoughts

I am deeply saddened by the tragic deaths that served as the catalysts for this blog post. I don’t scare easily, but stories like those truly scare me.

Carbon monoxide poisoning strikes with little warning… and with no odor, or color, or taste. The only way to protect your family from this silent killer is by:

  • installing quality CO detectors in appropriate locations throughout your home
  • replacing their backup batteries on schedule
  • testing them regularly with aerosol spray (not the test button)
  • replacing the CO detector after 5 years of use — or when the aerosol test fails, whichever comes first

Even though I’m a DIY junkie, I will admit that there are some maintenance and DIY projects that can be put off until the weather, or schedules, or finances are more favorable. This is not one of them.

Go to Amazon right now and search all their carbon monoxide detectors. Find the right one(s) for your needs and purchase the appropriate number of units for your house. They’re not expensive. Well-reviewed CO detectors are available with free shipping for less than $15 each.

Seriously. Please. Do it. Right now. Right. Now.

As always, I welcome your comments, feedback, and suggestions below.