air v carbon monoxide

[janicedoig]

Is carbon monoxide lighter than air. ie would it be above breathable air or below in a gas filled room?

[theprof]

Carbon monoxide has a density of 0.96716 at a temperature of 20 degrees Centigrade. Air has a density of 1.00000 at the same temperature.

So, you can consider carbon monoxide to have virtually the same density as air at a room temperature of 20 degrees Centigrade. Expressed as a percentage (for the pedantic) carbon monoxide is actually 3.284% lighter than air at the teperature quoted.

Breathability is a different matter altogether. Whenever two or more gases occupy the same space, diffusion of gases invariably occurs. This is accelerated by such things as moving air-currents in the room and general air turbulence. So carbon monoxide introduced into a room would fairly rapidly diffuse into the room atmosphere, making the whole atmosphere poisonous.

The density of carbon monoxide increases as the temperature of the environment decreases. At zero degrees Centigrade, it is substantially heavier than air and would indeed temporarily form a layer beneath air in a room. However, diffusion would stiil allow the gas to permeate some of the air in much the same way as you spray of air-freshener from an aerosol can in a room.

So all in all, if there's carbon monoxide in a room, or you suspect its presence, get out as fast as you can.

.

[Hippy]

THEPROF beat me to it with the message that to all intents CO mixes and does not form a layer.

It might be helpful to note that the medical symptoms of CO poisoning feel a bit like flu, without the nasal congestion and fever. Headache, nausea, and listlessness are tell tale signs. You feel faint and reluctant to do anything because your mental state alters. DO NOT IGNORE, as you could be lulled into sleep so easily, and that way leads death. Many smoke alarms also detect CO and give a series of short beep alarms to let you know.

Get out of the room, open doors and windows get outside and breath loads of fresh air. Later, when you feel safer, try and turn off all burning appliances that might be the cause. Usual culprits are gas fires or heaters with impaired flue ventilation, charcoal burning indoors (NEVER DO THIS), vehicle exhaust (Never run vehicles in a garage, even with the door open, the gas seeps into the house where it is invariably un-vented), and un-vented wood burning or oil burning stoves.

DON�T use a gas stove to heat your home, even for a short time.

DON�T ever use a charcoal grill indoors; even in a fireplace.

DON'T sleep in any room with an un-vented gas or oil burning heater.

DON�T use any petrol or diesel engines (mowers, weed trimmers, snow blowers, chain saws, small engines or generators) in enclosed spaces.

DON�T ignore the symptoms, especially if more than one person is feeling them. You and your companions could lose consciousness and die if you do nothing.

[Gef]

Just a couple of thoughts for theprof.

At sea level and 20C the density of dry air is 1.2 kg/cubic metre not 1.00000.

Carbon monoxide gets denser as it is cooled but so does air.

Not disagreeing with your answer, just wondering where you got your figures from and what units you were using.

[kempie]

I presume theprof is using a figure which indicates relative density to air rather than the absolute density as measured in any specific units.

[theprof]

You're right kempie - I was using using a baseline figure to illustrate the comparative density of air to carbon monoxide. It is often easier to appreciate the differences in density between two gases when expressed in this manner.

I had hoped that this would be evident from the fact that I not expressed the density in any particular mass per volume units although I will concede I could have made it clearer.

Oddly enough Gef, the figure I quoted came from memory as reviewed a paper fairly recently on the interaction of pressure, haemoglobin and carbon monoxide. I've telephoned the author of the paper, who told me that the figure was from Hawley. To quote from my own copy, under the entry for carbon monoxide, Hawley's dictionary states "D 0.96716 air = 1.0"

Air does indeed get denser as its cooled, just like carbon monoxide. However carbon monoxide will be more dense than air at lower temperatures and will form a layer beneath air, which was the point I was trying to make. Much published research confirms this.

[theprof]

I should have added to the last paragraph that the carbon monoxide and air layer will eventually diffuse into one another in accordance with Grahams Law Of Diffusion.

[thedwag]

So - What happens when the outside air temperature is at say -1C and say the living room is damn cold - the occupier is using a mobile gas heater in an endeavour to keep a room warm, they have found that they are feeling a draught from the windows and the door into the room and go about sealing up the windows and draught prooffing the door which soon gets the room feeling nice and snuggly and they settle down on the settee to watch TV - What happen's next?