Rank: Guest 
|
Posted By Peter MacDonald
Hi
Come someone please provide a clear and concise definition of 'gas' and 'fume' and explain in laymans terms the diference between the two.
Thanks in advance
Peter
|
|
|
|
|
|
Rank: Guest
|
Posted By Kenny Bedgood
Peter
How I've thought of it that a gas is just that. e.g. oxygen, nitrogen etc. in a pure state.
Fume is something emitted from processes such as welding, engine exhausts etc. There is still gas present, but in such examples there will be microscopic solid particulates. Thus changing it into fumes.
Hope this helps.
|
|
|
|
|
|
Rank: Guest
|
Posted By Stephen D. Clarke
I'll have a go at a definition:
Fume consists of solid particles of very small size, composed of atoms or molecules relatively loosely bound together, produced by condensation from a liquid or vapour. Fume is produced by condensation of metal vapour produced by, for example, hot metal soldering. So basically fume is made up of tiny solid particles, typically small enough to be readily breathed in.
A gas is a fundamental state or phase of matter (others being liquid, solid, plasma) composed of atoms or molecules that are relatively far apart moving freely in a constant, random motion and have weak cohesive forces acting between them, resulting in the characteristic indefinite shape and indefinite volume of a gas e.g. oxygen, hydrogen, nitrogen. Typically what we normally think of as a gas is at ambient temperature because when a substance is cooled down it will change from gas to liquid to solid.
Hope that makes some sense.
|
|
|
|
|
|
Rank: Guest
|
Posted By Adrian Watson
Dear All,
The standard occupational hygiene definitions are;
A gas is defined as a substance above its critical temperature and a vapor as the gaseous phase of a substance below its critical temperature, the term “gas” is usually applied to any material that is in the gaseous state at 20°C and 760 mmHg pressure; “vapour” designates the gaseous phase of a substance that is ordinarily liquid or solid at 20°C and 760 mmHg pressure.
A fume is defined as the solid particles generated by condensation from the gaseous state, generally after volatilization from melted substances and often accompanied by a chemical reaction, such as oxidation.
Regards Adrian Watson
|
|
|
|
|
|
Rank: Guest
|
Posted By Adrian Watson
Dear All,
The standard occupational hygiene definitions are;
A gas is defined as a substance above its critical temperature and a vapour as the gaseous phase of a substance below its critical temperature, the term “gas” is usually applied to any material that is in the gaseous state at 20°C and 760 mmHg pressure; “vapour” designates the gaseous phase of a substance that is ordinarily liquid or solid at 20°C and 760 mmHg pressure.
A fume is defined as the solid particles generated by condensation from the gaseous state, generally after volatilization from melted substances and often accompanied by a chemical reaction, such as oxidation.
Regards Adrian Watson
|
|
|
|
|
|
Rank: Guest
|
Posted By Merv Newman
Fume is particulate ie little lumps ie smoke. Gas is elemental or molecular ie O2, CO2,
With the above caveates on critical temperatures and changes of state.
KISS
Merv
|
|
|
|
|
|
Rank: Guest
|
Posted By Peter MacDonald
Much obliged to all.
Merv..... what does KISS stand for?
|
|
|
|
|
|
Rank: Guest
|
Posted By Johannes de Silencio
Keep It Simple, Stupid!
Nice simple definition that for the none specialist employee, Merv. It encompasses all the basic properties without blinding folk with the physics & chemistry.
I was still floudering round explaining PV = nRT at the time when you came up with that one!
|
|
|
|
|
|
Rank: Guest
|
Posted By Merv Newman
Keeep It Simple Stupid.
Well known phrase or saying. And no denigration intended of any of our correspondants.
Merv
|
|
|
|
|
|
Rank: Guest
|
Posted By Adrian Watson
Merv,
Fumes are not little lumps of smoke. Smoke is a mixture of gases and aerosols produced by the incomplete mixture of carbonaceous materials.
However, fume is a particulate aerosol, produced by condensation. As fume is only a little larger than gas molecules, it easily passes through the blood-gas barrier in the lungs. This is why metal fumes are more hazardous than larger particles which are trapped in the upper respiratory tract, swallowed and absorbed through the digestive system. For example more than of 50% Lead Fume is absorbed in the lung whilst about 10% of lead in the digestive system is absorbed.
Regards Adrian
|
|
|
|
|
|
Rank: Guest
|
Posted By Jonathan Breeze
Adrian,
Would it be closer to the mark to say a fume is comprised of nanoparticles of solid, a vapour or aerosol is microscopically fine droplets of liquid and a gas is free molecules of the same?
|
|
|
|
|
|
Rank: Guest
|
Posted By Adrian Watson
Yes.
Regards Adrian
|
|
|
|
|
|
Rank: Guest
|
Posted By Adrian Watson
Yes a fume is an aerosol nano-particle. Aerosols are a suspension of solids in a gas, normally air for our purposes.
A vapour and a gas are the same; free molecules in air. However, the gas molecules in a vapour are from a substance which is normally liquid or solid at room temperature and pressures.
Regards Adrian
|
|
|
|
|
|
Rank: Guest
|
Posted By Peter MacDonald
Seems a simple question on gas and fume is now generating a lot of hot air!
Just Kidding!
Thanks again Pete
|
|
|
|
|
|
Rank: Guest
|
Posted By Jonathan Breeze
LOL.
The problem is there is a technical exam answer and a simple answer.
You want the simple answer and it's thrown us because life ain't simple!
Adrian has correctly hinted that there are always exceptions to any simple definition.
He can't help that he's so highly trained!
|
|
|
|
|
|
Rank: Guest
|
Posted By Adrian Watson
Dear All,
I totally agree with the KISS principle and endeavour to keep things as simple and straightforward as possible. However, I also endeavour to heed Albert Einstein's warning to "Make everything as simple as possible, but not simpler."
Unfortunately, it is difficult to know where to start or where to finish in a discussion forum where there is a wide range of knowledge. If you put in too much information, you risk being considered a pompous twit. However, if you put in too little information you risk misleading the reader. I would rather be considered a pompous twit than deliberately mislead the reader. Where there is far too much information I attempt to direct the reader to further information.
Regards Adrian Watson
|
|
|
|
|
|
Rank: Guest
|
Posted By Merv Newman
Whats a aerosol nano-particle daddy ? Look, I know the answer (ten to the minus ninth) but not everyone does. Do they ? And don't aerosols come in tins ? Like underarm deodorant.
Ok, I was a bit sloppy with the smoke/fume thing. But, depending on whom you are talking to, does it always matter ?
Merv
|
|
|
|
|
|
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.