[GSBN] Carbon Monoxide: A Thanksgiving Story

Derek Stearns Roff derek at unm.edu
Sat Nov 29 12:22:23 CST 2014

And a Cautionary Tale…

Around 2 PM, my sweetheart and I arrived at my brother’s girlfriend’s house, for Thanksgiving Dinner.  We were the first guests, and within about ten minutes of our arrival, our conversation was interrupted by a brief, but loud electronic chirping.  One minute later, the sound repeated.  To me, it sounded like the low-battery warning of a smoke detector.  They always pick the most inconvenient time to start their complaining.  The others agreed, but the hostess said she didn’t know she had a smoke detector.  She has only lived in the house for a few years, so we speculated that the battery might have just reached the end of its life.  However, we couldn’t see a smoke detector.  None the less, every minute, we got another chirp. 

We listened to the chirping, and each of us thought the sound was coming from a different place.  The wide intervals, and short duration of the chirp made it hard to localize the sound, but wherever we stood in the room, the sound seemed to be coming from moderate distance, probably from up high, and part way across the room.  The search problem was exacerbated by the open plan of the great room, which was timber-framed with very high ceilings.  There were plenty of spots on tops of beams and behind metal reinforcing plates, where a smoke alarm might have been hidden by a previous owner.  

Other family members arrived, and joined in the hunt.  Someone wondered whether the local hardware store might sell a smoke detector detector.  Another pointed out that the house now had a built-in Pictionary timer.  We got out ladders, moved furniture and curtains, and removed the covers from the doorbell and thermostat.  Nothing.  The sound still seemed to be moving around the room, always nearby, but constantly out of reach.  My sweetheart suggested that it might be a carbon monoxide detector.  The hostess said that she didn’t have one of those, either.  

Ummmmm…  I did.  In my backpack, which I had set on the floor in the main room.  For some reason, none of us had heard the sound as coming from the backpack, nor from the floor level.  And in my defense, I had never heard this CO meter make a noise.  It is not the normal household CO detector.  I was not aware that it had this kind of alarm.  

So why was I carrying a special CO meter in my backpack?  That story goes back a couple of years, to an article that I read on Green Building Advisor.  The article informed me that both the Underwriters’ Laboratories and Consumer Product Safety Council’s (CSPC) guidelines for CO detectors forbid them from sounding an alarm below 70 ppm of CO.  According to the article, and other articles that I’ve read subsequently, this threshold was chosen, after pressure from industry and fire departments, “to avoid customer confusion and nuisance alarms”.  One of the points of irony is that many fire departments require fire fighters to use oxygen tanks, if they are working in a building with above 25 ppm CO.  The CSPC website says that death is possible from prolonged exposure to 150 ppm.  The EPA’s national ambient air quality standard 8-hour exposure limit is 9 ppm.  The current OSHA PEL is 50 ppm, and the NIOSH REL is 35 ppm.  See this link for many other limits and standards.  http://www.coheadquarters.com/ZerotoMillion1.htm

Meanwhile, various hospitals and medical groups warn that chronic CO exposure isn’t good for anyone, and even 10 ppm is a possible risk for infants and anyone with compromised respiratory systems.  There is a correlation reported on some sites, between low levels of CO and asthma problems.  As a result of reading this stuff, I bought a fairly expensive CO meter (~$190), which will show a reading of 1 ppm, and above.  I got it to check my Dad’s and Mom’s houses, since each of them has an older furnace and a compromised respiratory system.  I was pleased to find that their houses, and my house, showed 0 ppm on my meter.  

Since that time, I haven’t had much of a targeted use for my expensive meter.  However, I try to take it with me whenever I visit a friend’s house during the winter, because no one else I know has a sensitive CO meter, and no one ever knows what the CO status of their home is.  Almost all the houses that I visit have readings of 0 ppm.  I have found problems in four different houses of my friends, over the last three years.  Non-zero readings that I have taken in different houses have peaked at 7, 15, 23, and 35 ppm.  None of these readings triggered the audible alarm.  

At the Thanksgiving Dinner, the CO meter didn’t show a number.  It only said “High”.  Checking online, I found that this meter displays the word “high” when the CO level exceeds 50 parts per million.  I had never gotten a reading that high before.  Probably, the high CO level was caused by the (propane) stove, oven, or both.  As one might expect, they had been on all day, with cooking activities.  There isn’t a forced air furnace, and the water heater is in the garage.  We opened windows and doors (luckily, it was a warm day), and turned off the stove and oven.  This brought the CO levels down, and we completed our Thanksgiving Meal with no one reporting any noticeable effects.  Our hostess plans to try and find someone to test and repair all the gas appliances in the home, as soon as possible.  

It was quite a surprise to find that the CO levels were high enough to trigger the above 50 ppm audible alarm on my meter, with the meter in a closed backpack pocket.  I’d love to know what the actual peak ppm was, but I’m very glad that we had a sensitive meter to warn us of the problem.  [My meter is the 2012 CO Experts meter.  Their current model gives numeric readings from 0 - 100 ppm.  This meter has been well reviewed on many websites, but there are other well-rated options.]  

If you cook or heat with gas, wood, or any other combustion, consider checking your CO levels with a meter more sensitive than the usual hardware store CO detector.  

Happy Thanksgiving!


Derek Roff
derek at unm.edu

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