# How much Carbon Dioxide would be required to displace enough oxygen to prevent ignition?

In air, how much $\ce{CO2}$ would be required to prevent a match to light or a butane lighter to work?

I have a basement office that is unusable because of an apparent lack of oxygen, currently it is my guess that the oxygen is being displaced by $\ce{CO2}$.

A bit research suggests that it would take a reduction to around 14% for a safety match to fizzle out without any flame. But my naive estimate suggests 7% $\ce{CO2}$, and at that level isn't $\ce{CO2}$ deadly? And this isn't even accounting for the displacement of nitrogen, surely that would mean the levels of $\ce{CO2}$ would be even higher.

Would a 6% increase in $\ce{CO2}$ displace oxygen by only small percentage say 2% as it's only a smaller ratio of the atmosphere? Or would the presence of $\ce{CO2}$ contribute to the lack of ignition compounding the lack of oxygen?

See my related question on the DIY stack exchange

# UPDATE

An insepector from the local council has installed a data-logger, whilst he was in the basement he took a reading that I've attached below. When this reading was taken the air felt poor, but by no means the worst it's been, a candle wouldn't stay alight. An breathing during conversation seemed laboured. It looks like the assumption of displacement doesn't look correct, there's more to it. Here's the readings:

$\ce{CO2}$ 3.3% (0.04%)
$\ce{O2}$ 17.5% (20.8%)
Other 79.2% (unchanged?)

• This is the wrong question, you should ask What's the min amount of oxygen necessary for ignition? or something similar in fact ignition could be prevent even with nitrogen and CO2 % is very low then nitrogen %. – G M Apr 8 '14 at 9:39
• My current theory is that it's CO2 that's displacing the oxygen, possibly from a nearby dairy farm slurry pit. – Dog Ears Apr 8 '14 at 9:42
• Okay, But you can have 50% of $CO_{2}$ that is 1500 times the normal value and still light a match if there is oxygen.So your question doesn't have sense.. – G M Apr 8 '14 at 9:46
• So, as I said, the oxygen must be around 16% or lower! – Dog Ears Apr 8 '14 at 9:47
• @DogEars Considering that it's a basement office, I would think that humidity may also play a factor as basements are usually more humid than above-ground open enclosures. – qwersjc Apr 10 '14 at 1:10

The parameter you are asking about is called the Minimum Oxygen Concentration (MOC), and is a measurement of the minimum amount of oxygen present in air to propagate a flame. The amount depends on the fuel being burned, and varies from about 4% for hydrogen to about 18% for some solid combustibles.

Let us consider your example of butane, and round some numbers to make our calculations simple. Butane has a MOC of 12%. Normal oxygen content in air is 20%, with nitrogen and sundries making up the remaining 80%. Assume uniform mixing and displacement of gases is equal. In order to reduce the oxygen content to 12%, you need to introduce enough CO2 to make up 40% of the air content:

$O2 + N2 = 100$ =>20 + 80 = 100%

$O2 + N2 + CO2 = 100$ => 12 + (12*80/20) + CO2 =100%

However, let us consider a couple of other very significant points.

• An oxygen level of 12% is unsafe. Anything below 19.5% is unsafe. At levels of 12%, a person will have impaired judgement and coordination, and experience increased pulse rates. Prolonged exposure can have fatal consequences.

• A CO2 level of 40% is fatal. Full stop. Levels above 7% can cause loss of consciousness and just 10% can be fatal.

• CO2 is actually denser than air, so mixing of the main components is unlikely to be uniform. This means that higher CO2 concentrations will be found lower down in the room.

I hope you stay well clear of your basement until you have resolved this problem and have appropriate active ventilation installed, as well as possibly an oxygen monitor.

In the very least, get yourself a canary.

• If the partial pressure of $O_2$ is the same, does the level of $CO_2$ affect the ability of things to burn? If we replaced all of the $N_2$ with $CO_2$ but left the $O_2$ alone then it would be very bad for humans but wouldn't things burn just as well? Of course, it would be very different if we replace the $O_2$ with $CO_2$ and left the $N_2$ alone . – badjohn Jul 31 '18 at 12:55

As you know the atmospheric gasses concentration in dry air is very different, carbon dioxide normally is below 0.1%:

Assuming that Limiting oxygen concentration for ignite the wood of your match is 17 % and that the ratio between the atmospheric gas is preserved you have to find the factor ($x$) that multiplied by the oxygen content give you 17.

$$20.9646 \times~x = 17$$

Then you can multiply Argon%, Oxygen%, Carbon dioxide% etc. etc. for x and then find the % of the unknown gas subtracting to 100% the sum of all the gasses. In one formula: $$100-((Ar\%\times x)+ (O_{2}\%\times x) + (CO_{2}\%\times x) \ldots)= Unknown~gas~\%$$

The result is this:

So the unknown gas could occupy 18.8% of the volume of your cellar. This means that if it is $CO_{2}$ you could have several problem:

Within 1 minute of exposure to 20-30% $CO_{2}$, unconsciousness and convulsions occur in humans. blm.gov

If you calculate it with a LOC of 14% you have a $CO_{2}$ content of 33%, this content as stated long (credit to him) can kill you.

However for what I've read in your question there are not enough evidence that you are dealing with carbon dioxide, what I think is sure is that your cellar is not a safe place to stay.

CO2 Maximum Levels: The defined PEL limit per OSHA is 5000 ppm or 0.5% The OSHA STEL/IDLH is 40,000 ppm or 4%

O2 Minimum levels: The amount of Oxygen found in ambient air is approximately 20.9%, if O2 levels fall below 19.5% the air is considered to be oxygen deficient, and workers at this level would require oxygen enrichment of the work space. A level of 18% or less is considered to be an IDLH event.

You need to have outside air introduced to be able to work in this environment. Typically in a forced air HVAC you pull a small duct from outside the home to tie in with your air return. I would add a floor level air return in the cellar to your furnace and add a fresh air outlet at the ceiling level to introduce new fresh air to the cellar.