Dry Powder extinguishers are DANGEROUS on yachts.

[andygc]

Thanks, because I am a bit thick could you explain where I did not get everything straight ?

CO2 controls the urge to breathe and this is a lot of the cause of altitude sickness = complete nonsense. Bizarrely hardly bizarre, it is essential since it is CO2 production that determines the metabolic oxygen requirement, blood O2 saturation is not the primary driver of the urge to breather, that is determined by blood CO2 partial pressures and by the closely linked blood pH.

I am struggling to reconcile: "Carbon dioxide is not toxic. That is, it is in no way poisonous. " with the para that follows.

Helium and Nitrogen are not toxic. Breathe 100% He or N2, you still die. Sea water is not toxic. Put your head underwater and breathe it, you still die. CO2 has no toxic effect. It's potential to kill does not involve a toxic effect on tissues (unlike CO), it does not block metabolic pathways (unlike, eg, HCN), it kills through interfering with a physiological feedback loop.

 

[Ricd]

Helium and Nitrogen are not toxic. Breathe 100% He or N2, you still die. Sea water is not toxic. Put your head underwater and breathe it, you still die. CO2 has no toxic effect. It's potential to kill does not involve a toxic effect on tissues (unlike CO), it does not block metabolic pathways (unlike, eg, HCN), it kills through interfering with a physiological feedback loop.

I think you will find there is some dispute regarding this and a simple trawl on the internet does suggest toxicity.
See the link http://www.inspectapedia.com/hazmat/CO2gashaz.htm OK its not a definitive paper subject to peer review (sorry) but quoting from it -
"According to the newspapers CO2 is nontoxic and it is the decreased oxygen levels that kills. Using the equation above one can quickly conclude that adding 31 liters of CO2 would result in 24% CO2(almost instantly fatal) and 16% oxygen (equivalent with breathing at 2800 meters above sea level, which is not dangerous)."

 

[Ricd]

Here is another interesting paper fully referenced by the International Volcano Health Hazard Network.
http://www.ivhhn.org/index.php?option=com_content&view=article&id=84

 

[RAI]

I just (belatedly) read the article in February's PBO "Fire in Fecamp". 10 small extinguishers fired, three didn't work, fire continued until the brigade arrived. Lucky it happened in harbour.

 

[Jegs]

Firetrace

Just in case anyone missed it, I found Divemaster's contribution, reference above, to be a particularly useful contribution.

Thank you D,

John g

 

[DogWatch]

Wow. I've never heard of this. I always imagined that walking into a space full of CO2 would be like walking into a space full of nitrogen or a hard vacuum - a slow suffocation.

But then the "gasp" response is triggered by CO2 buildup so I guess discomfort and panic might be the result - but instant knockdown?

I can't find it now, but on a natural history film I saw a few years back there was a dip in a jungle type environment; I can't recall if it was due to peat or volcanic activity but this dip had extreme levels of CO2 lying naturally at the bottom. It was only a few inches (the CO2 level) so in most cases animals were not affected.

They showed a lizard wander aimlessly into the dip, you could see the CO2 as it was like a mist, the moment the lizard took it's first breath in the mist it's tongue and pink skin in its gagging mouth turned blue (I had never seen anything like this before). One breath and this air breathing animal was fighting for it's life.

Interestingly, the lizard actually managed to back out and breathe again, recovery IIRC was actually amazingly rapid.

I accept that we are not lizards, but as a fellow respiratory type creature, I decided there and then that CO2 would have no place on my boat. Added to that, CO2 is BC, foam (AFF) is AB, the bucket is A.

My dry powder fire extinguishers are ABC, I have used one in anger, I will always carry dry powder as our primary extinguisher (unless something proven and better comes along).

 

[DogWatch]

I just (belatedly) read the article in February's PBO "Fire in Fecamp". 10 small extinguishers fired, three didn't work, fire continued until the brigade arrived. Lucky it happened in harbour.

I will personally only buy branded units... I have put my trust with kidde (available at COSTCO I bought for that reason), but I would also trust chubb and a few others. I would need to hunt the article, but were the duds in PBO's test not cheapo 'Isle of lidl' type units?

 

[RAI]

... but were the duds in PBO's test not cheapo 'Isle of lidl' type units?

No test, it was a real fire on a boat in Fecamp marina. The extinguishers came, in part, from neighbouring boats.

 

[DogWatch]

No test, it was a real fire on a boat in Fecamp marina. The extinguishers came, in part, from neighbouring boats.

Maybe it was sailing today then, but one of them did run tests on extinguishers for boats. I seem to remember there were some duds when the fireman hit the tits.

 

[kesh]

Helium and Nitrogen are not toxic. Breathe 100% He or N2, you still die. Sea water is not toxic. Put your head underwater and breathe it, you still die. CO2 has no toxic effect. It's potential to kill does not involve a toxic effect on tissues (unlike CO), it does not block metabolic pathways (unlike, eg, HCN), it kills through interfering with a physiological feedback loop.

that's a narrow and unusual definition of toxicity. the usual one is a substance that can harm an organism by any action on the molecular scale. your examples are silly because helium and nitrogen aren't the causes of the harm, absence of oxygen is. this isn't the case with CO2.

though in fact there is such a thing as nitrogen narcosis.

anyway it's the dose that makes the poison, not the compound, the father of toxicology paracelsus tells us.

 

[whipper_snapper]

CO2 controls the urge to breathe and this is a lot of the cause of altitude sickness = complete nonsense.

I am afraid you are wrong there, or at least we are down to quibbling over definitions.

Altitude sickness is a vague term that covers a range of problems. But one of more common is suppression of breathing due to inhibition of the breathing impulse due to low plasma CO2 levels caused in turn by rapid breathing in reduced O2 which blows off CO2. Effectively it alters the normal CO2/O2 relationship. This causes very unpleasant symptoms in which a sleeping person stops breathing and awakes gasping. That is also the reason why it may be argued that CO2 is an odd cue for the breathing impulse. It is of course completely different to HAPE and HACE but most people would categorize it as mountain sickness.

Helium and Nitrogen are not toxic. Breathe 100% He or N2, you still die. Sea water is not toxic. Put your head underwater and breathe it, you still die. CO2 has no toxic effect. It's potential to kill does not involve a toxic effect on tissues (unlike CO), it does not block metabolic pathways (unlike, eg, HCN), it kills through interfering with a physiological feedback loop.

Hmm. I am not aware of a formal definition of toxicity that distinguishes "toxicity" due to a toxic effect on tissue from "toxicity" through interfering with a physiological feedback loop. I suspect that if you examined the modes of action of many toxic substances, you would have trouble categorizing them one way or the other. Both kill you by acting directly on your biology, unlike He and N2 which can only kill you by depriving you of O2.

You may be right and there may be a distinction. But your Helium and nitrogen examples perfectly illustrate the difference between a gas which kills through some kind of broadly "toxic" effect and a non-toxic gas. After all, how do you fancy breathing 80:20 CO2:02 ?




EDIT
In fact the more I think about it the less sense your distinction makes sense. What about the whole category of toxins that work by blocking receptors? Are they toxic by your definition ? They don't cause any direct tissue damage, but they include some pretty nasty neurotoxins. Indeed CO itself does no direct damage, it just occupies the Hb O2 binding site rather avidly. There are toxins that directly damage, drilling holes in membranes for instance, but most of the tings I woiuld call toxins work by some indirect interaction especially blocking receptors and mimicking effector molecules (extra marks available for distinguishing those two!).

 

[Divemaster1]

Just in case anyone missed it, I found Divemaster's contribution, reference above, to be a particularly useful contribution....

Thanks ... I tend to think practical rather than technical....

In case of Fire, I want to alert all onboard and get them to relative safety, alert someone (coastguard, fire service or whatever)... and have safe area behind me before I would try to fight a fire which have caught hold. I do not wish to have to think if the extinguisher to hand can be used or not, which now makes this thread more theoretical than practical.... interesting though..

 

[Heckler]

Thanks for the brickbats. I was too busy earlier, but as you asked, here’s the short version:

The transfer of oxygen from atmosphere to tissues depends on binding with haemoglobin (Hb). That binding is described by a graph, the oxygen dissociation curve. The curve relates the partial pressure of oxygen in alveolar (ie lung) gas or body fluids to the saturation of Hb binding of oxygen. The graph shifts to left or right, depending on the pH of blood. Decreasing pH (acidification) shifts it to the right, which means Hb releases oxygen. Increasing pH (alkalisation) shifts it to the left, which means Hb binds more oxygen.

In simple terms, the rate and depth of respiration are controlled primarily by the level of CO2 in the blood (hypercapnic drive). This is a good thing. CO2 is what you make when you use energy, respiration is how you get rid of it.
When you are in an oxygen depleted environment you add hypoxic respiratory drive, that is, the low level of oxygen in the blood is detected and respiratory effort increases. This reduces CO2 levels in the lung and pulmonary circulation, makes the blood there more alkaline and shifts the dissociation curve to the left – thus binding more oxygen. This is another good thing. In the tissues, where work is done, CO2 levels are higher. Capillary blood is more acidic than arterial blood. The dissociation curve shifts to the right. Hb releases oxygen to the tissues. This is another good thing. In the atmosphere in which we live this system works well. It works well in people who normally live at sea level up to about 10,000 feet above sea level. This system for controlling respiration allows man (and animals) to live in a wide altitude range despite substantial variations in atmospheric pressure. It is most definitely not an example of evolution's inherent stupidity.

Carbon monoxide binds preferentially to Hb. That is, it is bound much more strongly than is oxygen. If there is sufficient CO to block O2 uptake, you die. It is potentially lethal at quite low concentrations. There is a Wikipedia article that gives the figures.

Carbon dioxide is not toxic. That is, it is in no way poisonous. Forgive me if this now gets technical, but I don’t feel like rewriting something I wrote elsewhere. sats=oxygen saturation, minute volume=the volume of air shifted by the lungs in one minute

If you breathe a CO2 enriched atmosphere you will stimulate the hypercapnic drive of respiration. Normal air is effectively 0% CO2. Breathing 2% gives an increase of about 25% in respiratory minute volume, and increases alveolar pCO2 by a couple of mm. Thus, a trivial effect on pO2. Breathing 4% CO2 doubles the respiratory minute volume and brings the alveolar pCO2 up to about 44 mm, so again only a small decrease of pO2. Even with the rightward shift of the dissociation curve due to the slight acidosis, you are still well up on the plateau (the top of the curve is almost flat – another good thing) with a haemoglobin saturation close to normal. Breathing 6% CO2 the minute volume almost quadruples, but the alveolar pCO2 only gets to about 50mm, which would mean a drop in pO2 to 93mm and sats should still be up at 94-95%. You have to have inhaled CO2 above 7% before things go badly wrong.

When you stop breathing CO2 enriched air the return to normal respiratory rate is rapid - it take only a few breaths to get the arterial pCO2 back to normal. CO2 has no toxic effect on gas exchange in the alveoli.

If you remain in an atmosphere with CO2 levels above 7% you will rapidly become exhausted by respiratory effort whilst being significantly hypoxic.

Although whipper_snapper may not have got everything straight, he was dead right about CO2. If you are in an atmosphere with high concentrations of CO2 you will die, and do so quickly. For skipper_stu, indeed CO can do this, but so can CO2. The difference is that for CO you only need a low concentration (1.28%), whereas for CO2 you would need a much higher concentration.

If somebody knows the STP equivalent volume of CO2 in an extinguisher and the volume of the boat cabin they want to use it in, they should be able to work out the likely CO2 concentration when the extinguisher is fired.

Using your argument its a bit like saying that water is toxic, yet we use it to fight fires. The argument is now a pissin contest, to see who can come up with ever more bizarre facts to further their cause!
Bottom line, a big breath of CO and you probably die even if moved to an oxygen enriched atmosphere, a big breath of CO2 and you catch your breath and live, a big breath of water and you probably die!
Stu

 

[Ricd]

Victims of carbon dioxide (CO2) poisoning die of hypercapnia (acidosis) a condition in which there is too high a buildup of carbon dioxide in the blood. Sounds pretty toxic to me

 

[Heckler]

Victims of carbon dioxide (CO2) poisoning die of hypercapnia (acidosis) a condition in which there is too high a buildup of carbon dioxide in the blood. Sounds pretty toxic to me

A lung full of water is "pretty toxic" Read my post again!
Stu

 

[Ricd]

A lung full of water is "pretty toxic" Read my post again!
Stu

People who drown have no water in their lungs..facts again

 

[Ubergeekian]

People who drown have no water in their lungs..facts again

Some people who drown have no water in their lungs. Many do. It depends on the strength of various reflexes.

 

[Heckler]

People who drown have no water in their lungs..facts again

Stop diggin!
Stu

 

[andygc]

A final input, and then I lose interest

Altitude sickness is a vague term that covers a range of problems.

No it isn't, it is a synonym for acute mountain sickness and is a condition attributed to the hypoxia that occurs at altitude.

But one of more common is suppression of breathing due to inhibition of the breathing impulse due to low plasma CO2 levels caused in turn by rapid breathing in reduced O2 which blows off CO2.

That is not altitude sickness, that is a normal physiological response to a high-altitude, hypoxic environment

That is also the reason why it may be argued that CO2 is an odd cue for the breathing impulse.

The physiological systems for controlling respiration evolved in the pressure environment that extends from sea level to about 10,000 ft above sea level. If the system doesn't support life very well at high altitude that is not a fault of the system, it demonstrates the dangers of going into environments that are outside the design parameters of the organism. I have already explained why hypercapnic drive provides a good method of controlling respiration.

EDIT
In fact the more I think about it the less sense your distinction makes sense. What about the whole category of toxins that work by blocking receptors? Are they toxic by your definition ?

Of course. Also, none of them is a normal constituent of the human body. CO2 is. High concentrations of CO2 are "toxic" in the same was as are low concentrations of O2: they cause derangement of a normal physiological process. I have checked my dictionary, and to be a toxin something must be a poison. I don't see how CO2 can be regarded as a poison.

People who drown have no water in their lungs..facts again

and that is complete nonsense. People who die before they fall in water have "dry" drowning. People who die of drowning have water in their lungs. That's how the pathologist can tell the difference.

 

[VicS]

Thank you andygc for your explanations ... and sorry about the earlier brickbat.