How does a wet cloth really help (scientifically) to survive an airplane crash?

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 is readily absorbed from the lungs; symptoms of poisoning begin within seconds to minutes. The odor of hydrogen cyanide is detectable at 2-10 ppm (OSHA PEL = 10 ppm), but does not provide adequate warning of hazardous concentrations. Perception of the odor is a genetic trait (20% to 40% of the general population cannot detect hydrogen cyanide); also, rapid olfactory fatigue can occur. Hydrogen cyanide is lighter than air. Children exposed to the same levels of hydrogen cyanide as adults may receive larger doses because they have greater lung surface area:body weight ratios and increased minute volumes:weight ratios."

"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:

"To limit the effects of toxic fumes, a wet cloth should be placed over your nose and mouth (a headrest cover or any other available fabric is suitable). Use water, soft drink or other non-alcoholic beverages to moisten the fabric."

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.

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.

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.

I also would have assumed the opposite, had I not read the articles, which prove our assumptions invalid.

The other articles on cabin fires went into nice detail as to how hydrogen cyanide acts as a cellular asphyxiant by binding to mitochondrial cytochrome oxidase.

They explicitly stated that smoke particles are not deadly in an airplane crash.

So, what you, or I, would have assumed about smoke itself being deadly, is apparently wrong.

If you still think your (and my) initial assumption is right, then what we need is an article about cabin fires which says both that the smoke particles are deadly, and, that a wet cloth reduces them.

Otherwise, we're just making non-scientific assumptions.

Science isn't what you are I guess. Science is what can be tested & proven.

I'd be glad if you can find a tested/proven article on airplane fires which says that smoke particles, in and of themselves, constitute a life-threatening danger in the time it takes to exit a burning airplane.

We found more than a half dozen sources, including scientific papers, none of which said that the smoke particles were the immediate danger in cabin fires - nor did we find anything that said a wet cloth filters them out.

If we are to assume smoke particles are a life-threatening danger, we'd have to find at least one scientific article that said that the particulate matter itself could kill us in the time of a cabin fire.

Even then, we'd have to know that a wet towel would filter out those particles.

I looked for papers backing up our (apparently erroneous) assumptions. I can't find any.

I agree that we don't have actual ppm levels documented yet, but, we do know that the hydrogen cyanide gas is deadly within minutes.

One of the papers said death ensues within minutes.

Another one discussed how a hundred people died, none of whom had traumatic injury, all of whom died from the toxicity of the gases in the fire.

What we don't know is the ppm concentration REDUCTION that a wet towel provides us.

I'm an organic chemist, and have handled cyanide. With the cloth, might be good to have it basic pH - say with sodium carbonate. I don't know solubility of HCN in water - is due to ionization energy. Sounds like a good thing to try, under the circumstances. gaseous ammonia is aggressively sucked up by water, due to ionization, and HCN is the same behavior. You'd have to look at pKa of HCN to tell - the stronger an acid it is, the more it will go into water.