carbon monoxide alarm 30 ppm image
mEl
i have an older furnace and i have a detector but i was wondering if the detectors detect small trace amounts of cm or only the major leaks.
Answer
Basically there are 3 levels that should activate the alarm 70 ppm, 150 ppm and 400 ppm depending upon how long the levels are detected.
I am a home inspector. I check CO as part of my inspection. Most furnaces and water heaters operating in normal conditions will have less than 20 parts per million in the flue stack (after the vent diverter). So 70 ppm CO is a pretty high level.
Kitchen ranges often exceed 400 parts per million on startup.
Ceramic log sets usually peg the meter at 2000 ppm.
From 1st Alert one of the leading manufacturers of home alarms:
<< WHAT LEVELS OF CO CAUSE AN ALARM?
Underwriters Laboratories Inc. Standard UL2034 requires residential CO
Alarms to sound when exposed to levels of CO and exposure times as
described below. They are measured in parts per million (ppm) of CO over
time (in minutes).
UL2034 Required Alarm Points*:
⢠If the alarm is exposed to 400 ppm of CO, IT MUST ALARM BETWEEN
4 and 15 MINUTES.
⢠If the alarm is exposed to 150 ppm of CO, IT MUST ALARM BETWEEN
10 and 50 MINUTES.
⢠If the alarm is exposed to 70 ppm of CO, IT MUST ALARM BETWEEN
60 and 240 MINUTES.
* Approximately 10% COHb exposure of 10% to 95% Relative
Humidity (RH).
The unit is designed not to alarm when exposed to a constant level
of 30 ppm for 30 days.
CO Alarms are designed to alarm before there is an immediate life threat.
Since you cannot see or smell CO, never assume itâs not present.
⢠An exposure to 100 ppm of CO for 20 minutes may not affect average,
healthy adults, but after 4 hours the same level may cause headaches.
⢠An exposure to 400 ppm of CO may cause headaches in average, healthy
adults after 35 minutes, but can cause death after 2 hours. >>
Basically there are 3 levels that should activate the alarm 70 ppm, 150 ppm and 400 ppm depending upon how long the levels are detected.
I am a home inspector. I check CO as part of my inspection. Most furnaces and water heaters operating in normal conditions will have less than 20 parts per million in the flue stack (after the vent diverter). So 70 ppm CO is a pretty high level.
Kitchen ranges often exceed 400 parts per million on startup.
Ceramic log sets usually peg the meter at 2000 ppm.
From 1st Alert one of the leading manufacturers of home alarms:
<< WHAT LEVELS OF CO CAUSE AN ALARM?
Underwriters Laboratories Inc. Standard UL2034 requires residential CO
Alarms to sound when exposed to levels of CO and exposure times as
described below. They are measured in parts per million (ppm) of CO over
time (in minutes).
UL2034 Required Alarm Points*:
⢠If the alarm is exposed to 400 ppm of CO, IT MUST ALARM BETWEEN
4 and 15 MINUTES.
⢠If the alarm is exposed to 150 ppm of CO, IT MUST ALARM BETWEEN
10 and 50 MINUTES.
⢠If the alarm is exposed to 70 ppm of CO, IT MUST ALARM BETWEEN
60 and 240 MINUTES.
* Approximately 10% COHb exposure of 10% to 95% Relative
Humidity (RH).
The unit is designed not to alarm when exposed to a constant level
of 30 ppm for 30 days.
CO Alarms are designed to alarm before there is an immediate life threat.
Since you cannot see or smell CO, never assume itâs not present.
⢠An exposure to 100 ppm of CO for 20 minutes may not affect average,
healthy adults, but after 4 hours the same level may cause headaches.
⢠An exposure to 400 ppm of CO may cause headaches in average, healthy
adults after 35 minutes, but can cause death after 2 hours. >>
Carbon Monoxide - Possible Sources?
Melissa
We live in the middle of a block of rowhomes in Baltimore City. For the second time in a month, the CO alarms have gone off at the houses on either side of us. This time, I was the only one of all of us who was awake. I had used hot water for a shower and washed a few dishes about an hour before. Firefighters checked our three homes, as well as the two other houses adjoining my neighbors. Readings were 30 ppm in one of the alarm houses and 90 in the other; zero in my home and the two other neighbors. When the firefighter turned on the hot water and held the meter next to my water heater for ten minutes, the highest reading he got was 8 ppm. We immediately replaced our CO alarm with a detector with a constant display, which is still showing 0 ppm after two hours in the room with the furnace (not running) and the water heater. The alley behind our homes is too narrow for a car or truck. We are at a loss for the source. Any ideas?
We have a Weber kettle grill and a Weber smoker, which we haven't used yet this year because we are having a particularly rainy summer. The alarm houses have gas grills, but this was 4.30 in the morning. Even if they both happened to have faulty tanks, they would have had to have been lit sometime around the time of the alarm, right? The 30 ppm house was gutted and rebuilt last year. The contractors were questionable, but the HVAC sub-contractors are reputable, as far as we know.
Answer
CO comes only from incomplete combustion of hydrocarbons (including charcoal), and not from any other sources. It is also lighter than air, and so may build up well away from where it is generated.
As you are in a row-house - if you share a chimney with a neighbor, and their flue is partially or entirely blocked, that CO may penetrate into your flue/house from next door. It is also possible that you may even share a flue, although that is unlikely.
Other sources might include a charcoal-fired grille near an open window or intake fan that might draw CO into the house. A partially blocked flue - or one that is blocked intermittently by a nest, or a loose brick or something similar such that the CO builds up at odd times.
I suggest that you check all your flues - all of them - and make sure that they are clear, free of any obstructions and draw properly. I suggest that while you are at it, you check any flues on your common walls and any that may vent near any of your windows at any level. You should also (if at all possible), see if your neighbors might be operating a charcoal device such as even a small hibachi inside their house - or may be using some other device such as a still, retort or other equipment that uses a fairly large flame, but may be in an area with restricted air intake.
NOTE ALSO: if you have your water heater in a tight basement, closet or other area without free access to outside (fresh) air in quantity, it might operate perfectly normally with the fire department standing around (all the doors open), but when you close the doors and restrict air-flow to it, start to produce CO in quantity.
You have done the right thing with the detector. Good luck with it in general!
CO comes only from incomplete combustion of hydrocarbons (including charcoal), and not from any other sources. It is also lighter than air, and so may build up well away from where it is generated.
As you are in a row-house - if you share a chimney with a neighbor, and their flue is partially or entirely blocked, that CO may penetrate into your flue/house from next door. It is also possible that you may even share a flue, although that is unlikely.
Other sources might include a charcoal-fired grille near an open window or intake fan that might draw CO into the house. A partially blocked flue - or one that is blocked intermittently by a nest, or a loose brick or something similar such that the CO builds up at odd times.
I suggest that you check all your flues - all of them - and make sure that they are clear, free of any obstructions and draw properly. I suggest that while you are at it, you check any flues on your common walls and any that may vent near any of your windows at any level. You should also (if at all possible), see if your neighbors might be operating a charcoal device such as even a small hibachi inside their house - or may be using some other device such as a still, retort or other equipment that uses a fairly large flame, but may be in an area with restricted air intake.
NOTE ALSO: if you have your water heater in a tight basement, closet or other area without free access to outside (fresh) air in quantity, it might operate perfectly normally with the fire department standing around (all the doors open), but when you close the doors and restrict air-flow to it, start to produce CO in quantity.
You have done the right thing with the detector. Good luck with it in general!
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