Thread: Dangerously high CO at oven

Yesterday's inspection was a little interesting.

I was operating and examining the oven and began smelling an odor. It was a 10 yr old GE brand that had been converted to LP. Decided to pull out the ol' Carbon Monoxide detector (yes I know CO is odorless).

The inside of the oven was at 5ppm - unusual to even get a reading, but OK, I'm still looking.

At the vent on top of the oven, the detector began climbing faster than the national debt. I turned off the oven at 214ppm and stopped inspecting it.

I'd like to think that somebody will be spared from CO poisoning. Sometimes it can be good to be an inspector.

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Originally Posted by JB Thompson

Yesterday's inspection was a little interesting.

I was operating and examining the oven and began smelling an odor. It was a 10 yr old GE brand that had been converted to LP. Decided to pull out the ol' Carbon Monoxide detector (yes I know CO is odorless).

The inside of the oven was at 5ppm - unusual to even get a reading, but OK, I'm still looking.

At the vent on top of the oven, the detector began climbing faster than the national debt. I turned off the oven at 214ppm and stopped inspecting it.

I'd like to think that somebody will be spared from CO poisoning. Sometimes it can be good to be an inspector.

I have to and maybe embarrassingly so do not know what the ppm is suppose to be at the vent of any type of gas stove. I always just looked for a clean, sharp blue flame in the oven. If it looks good and as you say has no odor from something burning off I let it go.

What should I be reading??? I just don't know.

I've had a similar circumstance. I was about to check the CO on a furnace in the basement of a home and had a constant level of 35ppm in the utility room. I tracked the source to the pilot light of an old stove set up in a lower level kitchen. It was giving out 300+ppm just from the pilot light.

There was a discussion a while back on this subject.Bob Harper and DavidR had some interesting input.Here's a link: http://www.inspectionnews.net/home_i...#post107034The discussion turned to CO Monitors, levels of reliability, etc.

Originally Posted by Ted Menelly

I have to and maybe embarrassingly so do not know what the ppm is suppose to be at the vent of any type of gas stove. I always just looked for a clean, sharp blue flame in the oven. If it looks good and as you say has no odor from something burning off I let it go.

What should I be reading??? I just don't know.

Mr. Menelly: The health effects of CO depend on the level of CO and length of exposure, as well as each individual's health condition. The concentration of CO is measured in parts per million (ppm). Health effects from exposure to CO levels of approximately 1 to 70 ppm are uncertain, but most people will not experience any symptoms. Some heart patients might experience an increase in chest pain. As CO levels increase and remain above 70 ppm, symptoms may become more noticeable (headache, fatigue, nausea). As CO levels increase above 150 to 200 ppm, disorientation, unconsciousness, and death are possible.

Originally Posted by Elliot Franson

Mr. Menelly: The health effects of CO depend on the level of CO and length of exposure, as well as each individual's health condition. The concentration of CO is measured in parts per million (ppm). Health effects from exposure to CO levels of approximately 1 to 70 ppm are uncertain, but most people will not experience any symptoms. Some heart patients might experience an increase in chest pain. As CO levels increase and remain above 70 ppm, symptoms may become more noticeable (headache, fatigue, nausea). As CO levels increase above 150 to 200 ppm, disorientation, unconsciousness, and death are possible.

Thanks for the info.

I kind of new all that. I was just wondering at the vent at the top of the gas range was there a particular PPM that was the standard. I did check out some researched info but in reality it just comes down to what you posted.

The oven being a temporary on time and the natural ventilation in the home I would find it difficult to see how a roast cooking in the gas oven would have any long term affects on most.

As far as vent-less gas fireplaces I think the entire idea is foolish. When ever I go into a home that has had one on for any period of time I have a hard time breathing. The air is so heavy it chokes you.

JB,
How long did you hold your CO tester to the oven vent?

I think if you would have continued checking for an additional 5-10 minutes you would found that the CO level dropped to 0. I have seen this before on ovens manufactured in the last 10-20 years. Oddly, older gas ovens don't seem to do this (no idea why). Once the oven gets heated up, the CO seems to disappear. I have no scientific or technical explanation, just an observation based on experience.

Originally Posted by Ted Menelly

I have to and maybe embarrassingly so do not know what the ppm is suppose to be at the vent of any type of gas stove. I always just looked for a clean, sharp blue flame in the oven. If it looks good and as you say has no odor from something burning off I let it go.

What should I be reading??? I just don't know.

Keep in mind I don't normally check for CO, but I carry a CO monitor clipped to me for my own health and safety.

Terry, that is interesting information. I can't remember how long I operated the oven. I do remember turning it on and then doing some other things. I came back to b/c of the smell. However, it was probably no more than 5-8 minutes (???) Since you're saying it's fairly consistent, that's very good information to have.

I almost started it back up to retest it, but decided against it.

I'm also a fireman in dallas. We had a run the other day with the CO (in a namebrand hotel) at over 1500ppm. A man was transported to the hospital with CO poisoning. He had been exposed for several hours as he was in the room next door to the water heaters.

Originally Posted by Ted Menelly

Thanks for the info.

I kind of new all that. I was just wondering at the vent at the top of the gas range was there a particular PPM that was the standard. I did check out some researched info but in reality it just comes down to what you posted.

0 ppm is the standard. I normally do not get any readings at ovens, water heaters, furnaces or dryers.

Originally Posted by Ted Menelly

As far as vent-less gas fireplaces I think the entire idea is foolish. When ever I go into a home that has had one on for any period of time I have a hard time breathing. The air is so heavy it chokes you.

On the flip side...taking into consideration my previous posts....

I actually have a ventless fireplace and have never registered any CO on my detector nor on the one that is mounted to the wall.

Bruce

Originally Posted by JB Thompson

0 ppm is the standard. I normally do not get any readings at ovens, water heaters, furnaces or dryers.



On the flip side...taking into consideration my previous posts....

I actually have a ventless fireplace and have never registered any CO on my detector nor on the one that is mounted to the wall.

Bruce

Ah but it could as in any gas fired appliance. That is why people get injured/sick/dead.

I guess the question is what is low level CO. Any CO at all or ????????????

By the way I have seen countless bad installation of many manufacturers, vented or non vented fireplaces.

I think me choking is just in thinking it is a bad idea. The warm moist air in the home closes things up a bit

Lets see. You must vent a water heater and you must have combustion air coming from somewhere. All older installations in homes (of water heaters) was questionable at best before the new standards.

Fireplaces drawing air from outside but then venting into the home?????????? Makes no sense to me. Fireplaces tend to run much longer...sometimes all night...unlike the roast in the oven. Fireplaces are just a water heater with out the water tank on top.

Now that I go back to Davids other post I think I am talking myself into agreeing with him on many points.

Originally Posted by Ted Menelly

Ah but it could as in any gas fired appliance....

Agreed

Originally Posted by Ted Menelly

I guess the question is what is low level CO. Any CO at all or ????????????

Low is anything less than 9ppm; however, I believe that is an outdoor number.

The 9 ppm is the maximum allowable difference between what's measured in the outdoor/ambient air and and what's measured indoors. As for CO level dropping as an oven heats up - the flame will have impingement on the plate above the burner - this in turn drops the temperature of the flame which results in a less complete combustion of the fossil fuel. As the temp rises the combustion improves and therefore reduces CO generation.

I use to measure for CO but finally gave up - I just got sick and tired of having to explain to HVAC contractors and F.D. personnel what the proper protocols were for doing such measurements. I found it amazing how misunderstood CO is by those who should know. Too many times someone would come in as a follow up to my inspection and either say that I was wrong or just simply have no earthly clue what I was talking about. And people, being as smart as they are, just figured that the HVAC guy was the "pro" and must know what he's talking about and that dumb me was the ignoramus.

Originally Posted by Eric Barker

The 9 ppm is the maximum allowable difference between what's measured in the outdoor/ambient air and and what's measured indoors. As for CO level dropping as an oven heats up - the flame will have impingement on the plate above the burner - this in turn drops the temperature of the flame which results in a less complete combustion of the fossil fuel. As the temp rises the combustion improves and therefore reduces CO generation.

I use to measure for CO but finally gave up - I just got sick and tired of having to explain to HVAC contractors and F.D. personnel what the proper protocols were for doing such measurements. I found it amazing how misunderstood CO is by those who should know. Too many times someone would come in as a follow up to my inspection and either say that I was wrong or just simply have no earthly clue what I was talking about. And people, being as smart as they are, just figured that the HVAC guy was the "pro" and must know what he's talking about and that dumb me was the ignoramus.

What are the proper protocols? This thread may or may not be the place. You can email me or start a new thread

Originally Posted by Eric Barker

The 9 ppm is the maximum allowable difference between what's measured in the outdoor/ambient air and and what's measured indoors. As for CO level dropping as an oven heats up - the flame will have impingement on the plate above the burner - this in turn drops the temperature of the flame which results in a less complete combustion of the fossil fuel. As the temp rises the combustion improves and therefore reduces CO generation.

I use to measure for CO but finally gave up - I just got sick and tired of having to explain to HVAC contractors and F.D. personnel what the proper protocols were for doing such measurements. I found it amazing how misunderstood CO is by those who should know. Too many times someone would come in as a follow up to my inspection and either say that I was wrong or just simply have no earthly clue what I was talking about. And people, being as smart as they are, just figured that the HVAC guy was the "pro" and must know what he's talking about and that dumb me was the ignoramus.

In the example of the oven you gave, is it common to get readings above 200ppm? It was still climbing as I moved away and then shut the oven off.

Originally Posted by Eric Barker

I use to measure for CO but finally gave up - I just got sick and tired of having to explain to HVAC contractors and F.D. personnel what the proper protocols were for doing such measurements. I found it amazing how misunderstood CO is by those who should know. Too many times someone would come in as a follow up to my inspection and either say that I was wrong or just simply have no earthly clue what I was talking about. And people, being as smart as they are, just figured that the HVAC guy was the "pro" and must know what he's talking about and that dumb me was the ignoramus.

I would not give up. I had a discussion with the HVAC person that was servicing my hot air furnace, a BRAND name. He stated that the heat exchanger was crimped, not welded. They have replaced some already that allowed combustion gases to enter the HVAC ducting due to the crimps failing.

Eric, if you save one life----it's worth it.

Bruce, Let me get back to you on the 200 ppm. I just came home from a day at the ASHI BoD's meeting - my brain is toast!

Rich - I fully understand and appreciate your point. But I was beginning to actually lose business because of all the flack that was occurring over the reporting of CO that few contractors could substantiate. To be honest, it was a business decision to stop the measurements.

Originally Posted by JB Thompson

0 ppm is the standard. I normally do not get any readings at ovens, water heaters, furnaces or dryers.

Where are you testing JB?

If you are testing in the proper locations and consistently getting no CO readings I would highly recommend checking out your test equipment to see if it's functioning properly.

Originally Posted by Ted Menelly

Thanks for the info.

I kind of new all that. I was just wondering at the vent at the top of the gas range was there a particular PPM that was the standard. I did check out some researched info but in reality it just comes down to what you posted.

The oven being a temporary on time and the natural ventilation in the home I would find it difficult to see how a roast cooking in the gas oven would have any long term affects on most.

NCI protocol specifies no more than 50 PPM as read at the outlet of the flue collar on a gas oven after it has heated up.

Many times the common problem with high CO in gas ovens has to do with air shutter adjustments and plain old grease.

DavidR,

Glad you came to join this discussion!

Would you find this article technically correct? Current? Accurate?

(clickable link - its a pdf file)
http://www.karg.com/pdf/coairfree_article.pdf

Would appreciate your commentary and input.

Thank you in advance!

H.G.

A few things I noted:
they used empirical calculations instead of actual in vivo measurements
They used 'average' values instead of actual values. These can vary tremendously when comparing your typical range/ oven with the newer commercial grade units being illegally installed into homes.
The discussions about ambient CO values are averaged calculations. A single story 3.0 ACH ranch house at sea level can be significantly different from a multi-story0.35 ACH house at 4,000 ft with strong local winds, which both can be drastically different from a multi-story home at sea level but with unsealed ducts.
They use pans of water but with the oven door closed on a bake cycle. Open the door, set the pan of water on the top rack and run it at 'broil' and watch the CO go through the roof. Now, put 5 people in the room walking back and forth and read CO at the exhaust.

DavidR teaches the NCI course so I'm sure he'll have some other commentary.

Bob Harper,

Glad to have you join the discussion.

I always enjoy your input, it is always welcomed and most appreciated.

Originally Posted by H.G. Watson, Sr.

DavidR,

Glad you came to join this discussion!

Would you find this article technically correct? Current? Accurate?

(clickable link - its a pdf file)
http://www.karg.com/pdf/coairfree_article.pdf

Would appreciate your commentary and input.

Thank you in advance!

H.G.

Glad I saw it to take a read, thanks for the welcome back!

I've always had some reservations on using CO air-free as the measurement gauge to judge appliance safety due to the fact it is a calculated value. It doesn't need to be ignored just understood and put in it's place more frequently.

Number one issue I see is a gas oven is an unvented appliance and should not be allowed inside a building period IMHO but we have to deal with the real world.

The as read value is what is being pumped into the building at that point in time and is what the occupants are going to be exposed to.
Like Bob pointed out infiltration rates, altitude, building variables, length of use, and manner of use will play a huge factor in this as well. The air free reading is a CO sample that will have absolutely no oxygen in that sample whatsoever. It is not what is being pumped into the space.

The other point that I rarely see mentioned is that the 800 PPM air free standard is based on a kitchen being the largest room in the building and have an air change rate of 8.0 ACH.
We simply don't see that type of air change rate in a residential kitchen.

There is more I just don't have any coffee in me as of right now.

DavidR,Thank you for your considered reply.Sincerely,H.G.

Originally Posted by H.G. Watson, Sr.

DavidR,Thank you for your considered reply.Sincerely,H.G.

You're very welcome H.G.

In response to your original question of me I do think there is some good accurate information in this article.
I do not agree with the way the representation between oven A and oven B is being presented to readers.

The air free reading in those scenarios is not what the occupants are being exposed to it is the as measured value.
There is a huge difference between both ovens while both are being portrayed as being identical due to air free readings that have been calculated.

I always love to read Bob's positions on this, I actually have a folder dedicated to his comments.
That type of wisdom would cost you a small fortune if you had to pay for it.

I am considering buying a MSA Altair Pro Single-Gas Detector. They run a little over $300. Does anyone have a suggeston for a better, similarly priced unit?

Originally Posted by DavidR

Where are you testing JB?

If you are testing in the proper locations and consistently getting no CO readings I would highly recommend checking out your test equipment to see if it's functioning properly.

I don't test (see earlier post). I keep it clipped on me for my own health. Therefore when I am in the same room as those appliances mentioned, I get a zero reading.

If I were to test, I suppose I would fire up the meter in a clear area and walk into the room with the appliance and test it near or at the flue collar or vent. I would also test near the flame area as well....just because.

Is that not right?

Originally Posted by JB Thompson

I don't test (see earlier post). I keep it clipped on me for my own health. Therefore when I am in the same room as those appliances mentioned, I get a zero reading.

If I were to test, I suppose I would fire up the meter in a clear area and walk into the room with the appliance and test it near or at the flue collar or vent. I would also test near the flame area as well....just because.

Is that not right?

That makes things a lot clearer, thanks for the clarification JB.

Good for you monitoring ambient air for CO, you never know what you might be walking into.

If you are going to test this is going to involve actual flue gas sampling in the undiluted flue gas before any drafthoods or barometrics. In the case of a gas oven you would need to test in the flue collar and then test each top burner with a pot of water on top of the burner while it's running to create impingement.

The funny thing about flue gas is you can have a vented appliance producing thousands of PPM of CO and have a room reading of zero PPM. With a gas oven it's all being dumped into the occupied space.

The only way to verify true safe operation is by taking multiple readings of the combustion gasses.

Originally Posted by Ed Wood

I am considering buying a MSA Altair Pro Single-Gas Detector. They run a little over $300. Does anyone have a suggeston for a better, similarly priced unit?

I've been using the Testo CO stick Ed and have been very pleased with it.
It's always accompanied by a NSI 3000 low level monitor for extra insurance.

Boy, you guys are really going to cost me with all this praise.....

BTW David, I have a folder on you, too! (and Jim)

Great discussion here and I want to discuss a few take-aways.

More than anything else is, protect yourself. Do Not walk into controlled atmospheres (read-buildings, vehicles, airplaces, and submarines) without some means of measuring ambient CO 'as read' and alerting you. This includes on airplanes (until the flight attendant makes you shut it off), hotels, public meeting rooms, etc. You should have it 'on' while driving in your car, even if just around the corner. You can velcro a low level monitor to the cab of your truck then snatch it off to bring inside for inspections for ex.

Understand CO, where it comes from, mechanisms of transport in buildings, and under what conditions it can become a problem. For ex., you do an inspection in the winter and do not detect any flue gas spillage at the WH draft hood. Does than mean everything is hunky-dory? What happens in the summer when there is no natural draft, often reverse convection, no flue gas losses from a furnace or boiler and the outdoor temps are much hotter? I see it all the time where WHs backdraft madly in the summer without any help. Now, turn on that whole house fan and the downdraft can extinguish a flaming match held at the draft hood. Same house, just different conditions. Go back to winter. The house is buttoned up tighter than a frog's rear end and it's 20F outside with a 20 mph wind against the house. You have combustion appliances in this home but you refuse to operate them and test for ambient CO ????? REALLY????? Wow! You notice the furnace ducts are not sealed nor is the filter rack at the return plenum. There are no test holes evident for measuring supply and return air for your delta T and ESP calculations as well as no test hole in the vent connectors of either appliance. Is this a Red Flag for you??? I sure hope so because it means nobody with proper training has been servicing this equipment.

Do you ever measure the CAZ and any MUA vents on the rare occasion you find them? Ok, let's say you run the math and *theoretically* there is sufficient MUA for all the appliances in the CAZ [you did take into acct. the clothes dryer didn't you? ;-)] Does this mean everything is hunky-dory and the MUA will work??? Don't hold your breath----or maybe on second thought you should. Codes do not guarantee performance and MUA is one shining example of this. ASHRAE did a decent study of passive MUA a few years back and basically proved it does not work reliably. Only mechanical MUA is reliable but even that must be interlocked with the equipment and of course, anything made by man can fail. Just a reminder, even when a house *passes" a code inspection, that means you scored a 'D-minus'. Now think that codes generally lag about 20 years behind knowledge and experience. We're still just begining to correct the sequelae from those initial weatherization measures back in the 1970's and '80s. All the while construction technology is changing very fast but with no in vitro or in vivo testing or quality assurance. The courts and hospitals are the Q/A review boards....

Lastly, in order to know where, when and how to test, you need professional training and certification. That means taking a course such as the National Comfort Institute's Carbon Monoxide and Combustion Certification, of which DavidR is an instructor. BTW, Dave and I have never personally met but stay in touch via these sites and email. He brings a unique perspective of being a top notched HVAC mechanical contractor who also is extremely knowledgeable about CO and house physics. He is a published author, too.

One last note about one of the evils of gas ovens taken from my EMS experience: during a power failure or if their primary heat source is not working, desperate people WILL light an oven and burn it unvented for heat. So much for the 4 hr. anticipated burn time...... Can you spell HBO? [hyperbaric oxygen therapy, which btw is being contested]

When I conduct home surveys for a Worst Case Depressurization Test and find no exhaust hood or one that simply recirculates back into the kitchen, I ask the homeowner if they consider the kitchen their "mother-in-law's suite". :-)

This has been a very informative thread. Thanks to all involved.

This chart was posted a long time ago during a similar discussion on this board. Here it is again for your use.

Stop Carbon Monoxide.

The chart shows a link of health effects from CO. It also has the UL standards for when a UL alarm will go off.

My concerns are chronic low level exposure. As a property owner you have the right to expose yourself to whatever you want. I don't think you should expose others to health risks.

We see things like the rise in asthma. You have to ask yourself how much of it is tied to our homes. We make homes tighter and we introduce more indoor pollutants. Things like carpets, OSB, press board furniture, plastics, low levels of CO, etc. We use different building materials that off-gas and are more suspectiple to mold. Reducing output of CO into the indoor air and ovrall ventilation should be higher on our lists to improve indoor air quality.

As far as unvented fireplaces I see them as a bad idea. You cant tell me there is 100% combustion. CO is formed with incomplete combustion. CO is not the only concern with combustion. There is a lot of water vapor given off. There are many other chemicals given off with burning gas or anything else. Why subject yourself

Originally Posted by Robert Hronek

As far as unvented fireplaces I see them as a bad idea. You cant tell me there is 100% combustion. CO is formed with incomplete combustion. CO is not the only concern with combustion. There is a lot of water vapor given off. There are many other chemicals given off with burning gas or anything else. Why subject yourself

I'll go further with that. An unvented fireplace consumes oxygen in the home. The longer the fireplace is used the less oxygen there will be and as a result the more CO that will be created because there will less and less oxygen for combustion.

Originally Posted by Eric Barker

I'll go further with that. An unvented fireplace consumes oxygen in the home. The longer the fireplace is used the less oxygen there will be and as a result the more CO that will be created because there will less and less oxygen for combustion.

Hello Eric:

Just as an observation, although your comments are perhaps intuitively sound, it would be virtually impossible to deplete the oxygen level in an home with a fire. Indeed, if you stood in the center of a burning house, completely engulfed in flames, there would still be virtually the same oxygen concentration in the home.

Cheers!
CaoimhÃ*n P. Connell
Forensic Industrial Hygienist
Forensic Applications Consulting Technologies, Inc. - Home

(The opinions expressed here are exclusively my personal opinions and do not necessarily reflect my professional opinion, opinion of my employer, agency, peers, or professional affiliates. The above post is for information only and does not reflect professional advice and is not intended to supercede the professional advice of others.)

AMDG

"Just as an observation, although your comments are perhaps intuitively sound, it would be virtually impossible to deplete the oxygen level in an home with a fire. Indeed, if you stood in the center of a burning house, completely engulfed in flames, there would still be virtually the same oxygen concentration in the home."

Caoimhin, would care to explain your position on this, esp. since it contradicts so many agencies, books, standards, lab testing , in vivo, etc.?
Thanks in advance,
Bob

I think the O2 level would depend on the air thightness level of the home and of the room would matter.

In a house fire if a window, door or exterior wall was comprised then I think it would be possible that enough fresh air could be introduced to keep the O2 levels near normal. If the fire occurs in an enclosed space it does use of the O2 and the fire is limited in its ability to grow based on how much fresh air is being drawn in. Think of brackdraft conditions for a fire that when a door opens the fire erupts due to the sudden availility of O2 combined with the vaporized fuel.

With a ventless fireplace I think the house would have to be extermely tight for it lower the O2 level but I can't say if it would affect burning of the gas. I do think that it is hard to be assured that there would be 100% efficiency. Anythings less than 100% means CO is being produced. I think it would be safe to say that a ventless fireplace produces CO.

I think we tend to focus on CO and whether it will set an alarm off. We seem to think if the alarm does not go off then everything is OK. A fireman is required to put on his breathing mask when CO reaches 40PPM but a family can live in a house with 40PPM because a UL listed detector will not alarm at this level. Doesnt make sense to me.

I may have my percentages incorrect but to sustain a fire you need at least 16% oxygen. Therefore if the fire is consuming "all" of the oxygen, it will go into smouldering state then eventually go out (beware of a backdraft).

I agree with you Robert on your assumption that a home would have to be very tight to deplete oxygen, but I have a ventless fireplace and have used my CO detector on it (0ppm).

Originally Posted by JB Thompson

I may have my percentages incorrect but to sustain a fire you need at least 16% oxygen. Therefore if the fire is consuming "all" of the oxygen, it will go into smouldering state then eventually go out (beware of a backdraft).

I agree with you Robert on your assumption that a home would have to be very tight to deplete oxygen, but I have a ventless fireplace and have used my CO detector on it (0ppm).

CO2 is one carbon atom and 2 oxygen adams so are you really using up oxygen in a fire or or burning oxygen or are you transforming it into a deadly gas. Instead of O or O2 it becomes CO2 or am I just making this up?

Originally Posted by Ted Menelly

CO2 is one carbon atom and 2 oxygen adams so are you really using up oxygen in a fire or or burning oxygen or are you transforming it into a deadly gas. Instead of O or O2 it becomes CO2 or am I just making this up?

No, I mean, yes, you are making this up, it's CO, carbon Monoxide which is produced by burning.

Plants give off CO2, I think, but I'm no chemist either.

Ordinary combustion produces heat, light, carbon dioxide and water vapor. If you have incomplete combustion, you can get CO and aldehydes. Plants take in CO2 and release O2 btw.

In the case with a ventfree burner, the room FiO2 can start to drop when the consumption of O2 exceeds the ventilation rate AND the CO2 emitted from the Fp displaces the O2. The more you burn, the more heavier CO2 falls to the floor displacing O2. You can easily read this with any working combustion analyzer by measuring the O2 level--the CO2 is just a calculation.

Ventfree burners have Oxygen Depletion Sensors or ODS. These are merely special safety pilots designed to dropout if the FiO2 reaches about 18.5%. As the oxygen level in the room drops, the flame speed of the pilot slows to where the flame is not impinging on the thermocouple, whose voltage drops below the threshold and it shuts off.

During a house fire in an unventilated room, the O2 is consumed until it drops below about 16% where the visible flame dies out. The room is now full of superheated air, CO,CO2 esp at the floor level and dozens of nasty compounds but no flaming combustion until someone opens a door or breaks a window. When done quickly, you get a backdraft or smoke explosion.

HTH.

Just as I was thinking that is why it seems a bit strange.

"CO is Carbon Oxide or carbon and oxygen. They are bonded in a compound. Co is Cobalt. Cobalt is a hard ferromagnetic silver-white bivalent or trivalent metallic element. An element is a pure substance that doesn't contain anything but itself. For example H (Hydrogen) is an element but H20 (Water) is not (it is a compound)."

Originally Posted by Bob Harper

Plants take in CO2 and release O2 btw.

Yes, that is correct, during photosynthesis, sunlight allows plants to produce Oxygen.

Plants also respire, taking in oxygen and giving off CO2.

At night, though, plants stop producing oxygen, but continue to respire, which gives off CO2. So it's best not to have a lot of plants in a bedroom.

But in general, the amount of oxygen produced is far greater than the amount of carbon dioxide, luckily for us. Thanks, Bob.