I'm not sure WHERE to ask this, but, how does a wet cloth work in an airplane crash anyway?
In step 3 at 45 seconds into this video shows it in use:
What's the wet cloth (scientifically) doing?
I'm not sure WHERE to ask this, but, how does a wet cloth work in an airplane crash anyway?
In step 3 at 45 seconds into this video shows it in use:
What's the wet cloth (scientifically) doing?
I agree with BobF; the wet cloth acts like a filter for both smoke particles and fumes that would be soluble in water.
During World War One, Canadian soldiers being attacked with chlorine gas (called "Mustard Gas" at the time because of it's yellow-green colour) were told to urinate into their handkerchiefs and to breathe through that wet cloth. The chlorine gas would dissolve in the water as it passed through the handkerchief, thereby keeping our troops safe and alive.
That nicely summarized FAA article explains:
- Smoke is a complex of particulate matter, invisible combustion gases & vapors suspended in the fire atmosphere.
- Inhalation of toxic gases in smoke is the primary cause of fatalities
- Carbon monoxide & hydrogen cyanide are the principal toxic combustion gases
- Carbon monoxide combines with the hemoglobin in blood and interferes with the oxygen supply to tissues
- Hydrogen cyanide inhibits oxygen utilization at the cellular level.
- Carbon dioxide is a relatively innocuous fire gas, increases respiration rate causing an increase in the uptake of other combustion gases
- Irritant gases, such as hydrogen chloride and acrolein, are generated from burning wire insulation
- Generally, carbon dioxide levels increase while oxygen concentrations decrease during fires.
And then finally, the article suggests:
- Cloth held over the nose and mouth will provide protection from smoke particulates;
- If the cloth is wet, it will also absorb most of the water-soluble gases (i.e., hydrogen cyanide & hydrogen chloride).
What's interesting is that the entire article doesn't discuss any dangers of breathing smoke particulates, so, why it bothers to mention a dry cloth is perplexing since we can safely assume that filtering out particulates is merely a convenience, and not a safety issue.
So, now we're left with the a WET cloth absorbing water-soluble gases. Of the two water-soluble gases, only hydrogen cyanide was listed in the article as being a safety issue (the other water-soluble gas was merely an irritant).
So, I guess we finally have the answer to "why the wet cloth?".
The WET CLOTH filters out (water soluble) hydrogen cyanide: "Hydrogen cyanide poisoning signs & symptoms are weakness, dizziness, headache, nausea, vomiting, coma, convulsions, & death. Death results from respiratory arrest. Hydrogen cyanide gas acts rapidly. Symptoms & death can both occur quickly."
Based on the one referenced FAA article, the dry cloth does nothing for safety, but a wet cloth reduces the water-soluble hydrogen cyanide gases.
Armed with the new keywords "wet cloth hydrogen cyanide", I find more on the toxicity of HCN over here:
"Hydrogen cyanide acts as a cellular asphyxiant. By binding to mitochondrial cytochrome oxidase, it prevents the utilization of oxygen in cellular metabolism. The CNS and myocardium are particularly sensitive to the toxic effects of cyanide."
"In the United States, antidotes for cyanide include amyl nitrite perles and intravenous infusions of sodium nitrite and sodium thiosulfate, which are packaged in the cyanide antidote kit."
But, what we need to know is how effective is the wet cloth in reducing the hydrogen cyanide gases in the cabin air.
And, here's what OSHA has to say about the dangers of HCN:
"[Hydrogen cyanide] is capable of bringing to a halt all cellular respiration".
"A few inhalations of high concentrations of HCN may be followed by almost instantaneous collapse and cessation of respiration."
"270ppm HCN is immediately fatal to humans" "181ppm HCN is fatal after 10 minutes" "135ppm HCN is fatal after 30 minutes" "110ppm HCN is fatal after 60 minutes"
"Humans tolerate 45ppm to 54ppm for 1/2 to 1 hour without immediate or delayed effects, while 18ppm to 36ppm may result in symptoms after exposure for several hours."
So, the key question is what the HCN concentrations are in a typical airplane cabin fire?
This flight safety PDF titled "Guarding the airways", is of interest:
It mentions only that the "wet cloth" prevents irritation, which we're not concerned with in this discussion.
They also explained that the "dry" heat of a cabin fire isn't of great concern: "the human body?s upper airway naturally provides significant protection to the lower airway and lungs against extreme heat from hot, dry air".
I'm pretty surprised about those findings, but they in this article specifically about guarding your airway during an airplane cabin fire.
This Airbus briefing discusses HOW to use the wet towels properly:
"Use wet towels, a wet cloth, or a head rest cover to reduce some of the effects of smoke inhalation. Instruct passengers to hold the wet towel/cloth over their noses and mouth and breathe through it." . This onboard emergency description mentions not to use ALCOHOL:
Given that alcoholic drinks are almost all water anyway, I wonder why they bothered to mention non-alcoholic drinks?
Does alcohol on the wet fabric do anything different with HCN?
Here they mention the heat inside your body during a cabin fire:
"In an aircraft accident that involves a fuel-fed fire, cabin air temperatures could be expected to reach 662 degrees F (350 degrees C) and higher. During inhalation, the air temperature might be reduced to between 360 degrees F and 302 degrees F (182 degrees C and 150 degrees C [respectively]) by the time the air reached the larynx"
They also mention the wet towel, although they talk about things that aren't safety related (apparently only the HCN is what we care about for the wet towel): ?Wet towels will filter out smoke particles, acid gases such as hydrogen chloride and hydrogen fluoride, and hydrogen cyanide. Breathing through clothing will also filter out smoke particles, but it will be less effective in filtering out acid gases and hydrogen cyanide. Neither a wet towel nor clothing will filter out carbon monoxide.?
As an aside, they mentioned that slowing down people for one second could cost one life, so, you don't want incapacitated people blocking the aisles.
Until I read the referenced articles, I would also have believed that filtering the smoke itself might have been a key safety issue.
But, we don't have any proof yet that smoke particles are anything we care about from an inhalation standpoint during a cabin fire.
In fact, this detailed article about all the negative effects of a fire mainly discuss "smoke density" as a visual impairment factor, and not as a critical inhalent (see page 39 of 47):
"Compilation of Data on the Sublethal Effects of Fire Effluent"
What we seem to care about is hydrogen cyanide, which is soluble in water. So the web towel apparently absorbs the HCN before you do.
On page 19 of 47, there is a table of the results of experiments of HCN gases on a variety of mammals, since they say only one human study was ever done. However, it's hard for me to extrapolate that table to what happens in a real cabin fire.
So, what we really need is the key datapoint: a. What is the concentration of HCN in a typical aircraft fire?
I would tend to wish to agree, since we've all heard about firefighters being treated for "smoke inhalation".
However, if particulates were a thread to life, why wouldn't the FAA and the other cabin fire articles previously posted mention smoke particles as anything more than an irritant?
Science, being what science is, doesn't always agree with our gut feelings.
Why do they always boil water when a baby is coming?
Do babies drink coffee?
(on TV)
Wow. That's good to have suggested. I certainly don't need any HCn or HCl.
How can we safely assume that? I'd assume the opposite.
I think what you have is a 3-page** article where they decided to be brief and not emphasize every problem. It's meant as advice and not a scientific paper, so they've taken a short, clear-cut approach.
**Less than 3, given the pictures and the line spacing.
Irritants irritate me. Anyhow, when HCl mixes with water it turns into hydrocholoric acid, one of the stronger acids. I don't want that in my lungs.
Yes, that's how they kill people in the gas chamber.
Hey, finally a benefit from my prostate problems. And truly, I was just now wondering where to get water for the wet cloth.
Do you remember Everett Dirkson and how he talked. I read many years ago that that was from being gassed in WWI, not enough to be killed obviously. Couldn't find a trace about that on the web, even though wikip or something remarked on his voice.
I think we're allowed to take judicial notice of everything else we've learned in our lives.
It is frequenty reported that someone dies of smoke inhalation. That's certainly something to care about. It may take longer than dying from cynanide, but it's still bad.
I'm pretty sure the amount of cyanide varies widely from one airplane fire to another, but there is no time to measure it.
Who says there is a typical aircraft fire wrt HCN?
Speak for yourself, John.
Yes, a rag soaked in the proper solvent will perform better than a dry rag. This is why you should have a properly labeled 4 oz bottle of dihydrogen monoxide in your carry on bag.
As others have said, they focused on the main cause of deaths in fires and that is the gases. That doesn't mean that particles are not also dangerous and life threatening. People that wind up hospitalized or die, typically die from a combined effect of everything to their lungs, ie gases, heat, particulate inhalation. It makes sense the gases are the most serious, but if you had some exposure to toxic gases, would you rather show up at the hospital with just that, or with your lungs full of soot and the irritation from that too? Some of these people just barely survive and whether they've inhaled particulates or not could make the difference.
Just because someone writing a brief article doesn't specifically mention something, doesn't constitute science.
LOL! just popped out for a spot of tea?
However the heat from the hot water and towels dilates the cervix really fast, but does increase the risk of infection.
Years ago, newspapers were used too, because they were steam press rolled and sterilized, but not today.
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