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Name: Jack
Status: other
Age: 40s
Location: N/A
Country: N/A
Date: Wednesday, April 02, 2003


Question:
What is the temp of a blue flame of burning Alcohol? Or how hot does alcohol burn? My name is Jack and I am a fire safety officer in a Hospital. We just put up hand sanitizers in our hospital. They have alcohol in them. There are questions on wether or not these hand sanitizers are safe or not. Thank You.


Replies:
1. Flame temperatures depend upon so many factors that it is impossible to reliably put a number on it. The temperature will depend upon the composition of the vapor and air, the configuration of the fuel source, the speed of the air, and so on...

2. I assume it is ethanol. If it is isopropanol the numbers will be about the same. The ignition limits of ethanol are 3.28 -- 18.95 vol. (alcohol/vol air)x 100. The Henry's law constant for alcohol is about 200 mol/l*atm. If Henry's law applies to the sanitizer the same as it does for water. (You can assume this if, as I believe, the sanitizer is predominantly water + alcohol + thickener) then a 10 gm /liter concentration of alcohol (I just guessed about what this concentration is.) is 2.17 moles/liter. Henry's law is: C = Kh*P, where P is in (atm) and C is in (mol/l). So P = C/Kh = 2.2/200 = 0.01atm. Using the ideal gas law: PV=nRT 0.01 atm corresponds to: n/V=0.01/0.082*298=4x10^4 mols/l The molar density of air (M.W. = 28) is (n/Vair)= 1atm/0.08*298= 0.04 mol air/l. So the Valc. / Vair ratio is 4x10^-4/ 0.04=0.01mol alc./mol.air. The lower ignition limit for ethanol is 0.0328.

So the estimate of the sanitizer vapor pressure is somewhat lower than the ignition limit. You might check with the manufacturer, but it appears not to be a fire risk. Also there are regulations regarding the ignition limits of a product. If ignition were a problem, they could not ship the stuff by common carrier -- which I doubt.

Vince Calder



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