Carbon Monoxide in enclosed spaces

[Jaybird180]

This wikipedia article says that CO is slightly lighter than air. I was wondering then what happens when CO is in confined spaces, like a hangar. Does it rise and eventually evacuate?

And secondly, how does CO behave at altitude? I would imagine that it's heavier than air at 8,000 MSL and that it would decend and thus pose little risk to aviation, but obviously that's wrong too.

Can someone explain what happens to the gas during altitude changes?

 

[Jim Logajan]

This wikipedia article says that CO is slightly lighter than air. I was wondering then what happens when CO is in confined spaces, like a hangar. Does it rise and eventually evacuate?

According to my math, the molecular weights of some common atmospheric gases are:

O2 = 32 (molecular oxygen)
N2 = 28 (molecular nitrogen)
CO = 28 (carbon monoxide)
CO2 = 44 (carbon dioxide)
H2O = 18 (water)

All the above are generally "well mixed" in the atmosphere and you would have to have very still air for a fairly long time for them to segregate into layers.

Only carbon dioxide is heavy enough to "pool" in low spaces; this is why dry ice is used to create fake fog in films and theaters. And only water is light enough to rise, causing clouds to form due to the temperature lapse rate with altitude.

 

[Capt. Geoffrey Thorpe]

Diffusion will mix it in eventually. But if you have a source of CO, you probably have something running, so you have some air mixing going on which is going to mix it up in your space.

There isn't much in the way of free pockets of CO lying around in the atmosphere - so, again, any CO you come across is probably from your engine. And, if you have a leak in your cabin heat muff, firewall, it is going to make it into your cabin. And, at altitude, where the O2 partial pressure is lower than at sea level, CO will get to you faster. Plus, if you fail to lean, you are running way rich and generating CO by the boat load. Result- CO is an issue for aviation

For most gasses, the ideal gas law tends to work reasonably well - PV = NRT Pressure * volume = Number of moles of gas * gas constant * absolute temperature.

As you go up, the volume for a given mass of air goes up and pressure goes down. The temperature changes as well.

It won't sink at altitude, because it is slightly lighter than air - if the air is less dense, the CO will be less dense as well.

 

[Geico266]

This is a good time of year to talk about CO in airplanes. Make sure your cabin heater is in good working order and that you have a CO tester to make sure. A cheap battery operated wall mount unit from Home Depot will work as a tester. Most even give you PPM so you can see if you have a leak or exhaust flowing back into the plane in flight.

CO is a very insidious deadly gas. You cannot smell it or taste it. Exposure can still be fatal even after getting fresh air. The gas in your system keeps O2 from exchanging with CO2 in your blood. ( If I remember right)

In any event CO is deadly. Get a tester before you pull the cabin heat handle.

 

[MAKG1]

Air is mostly nitrogen, and N2 has the same molecular weight as CO.

Your risk of CO separating out is the same as your risk of N2 separating out. Is that a risk in an enclosed hangar? Do you get oxygen enrichment from that?

 

[sferguson524]

This is a good time of year to talk about CO in airplanes. Make sure your cabin heater is in good working order and that you have a CO tester to make sure. A cheap battery operated wall mount unit from Home Depot will work as a tester. Most even give you PPM so you can see if you have a leak or exhaust flowing back into the plane in flight.

CO is a very insidious deadly gas. You cannot smell it or taste it. Exposure can still be fatal even after getting fresh air. The gas in your system keeps O2 from exchanging with CO2 in your blood. ( If I remember right)

In any event CO is deadly. Get a tester before you pull the cabin heat handle.

If i remember right, CO has a higher affinity to hemoglobin than O2.