Effects of dry ice causing a fatal accident? - need help 6

[ADT123]

I am currently investigating a fatal car accident which in which a person was carrying dry ice in an enclosed van. It has been many years since i studied this stuff and having found a similar issue on your forum I thought some the members expert knowledge may be able to assist me.

This is what we know:
Quanity of dry ice was 150Kg
Enclosed van had a volume of 3.72m3
Outside air temp was 27.8.C
Humidity 33%
Time lapsed 25 minutes

It was also worth noting that the dry ice was not stored in an insulated container rather cardboard function boxes.

The Dry ice was stored in 10 cardboard boxes 5 blocks of 3kg each each box.

I understand that dry ice sublimes at a rate of 8-10 pounds in 24 hours, but i have been told this is based on the dry ice being in insulated boxes.

Can anyone give me an indication, and show me how they worked it out, what the Oxygen levels would have been in the van at the 25 minute mark?
Thanks.

 

[nbucska]

The rate of sublimation is proportional to the surface
and 28 C is very hot.

I think instead of wasting time investigating it you should
submit the case for the DARWIN-AWARD.


<nbucska@pcperipherals.com>

 

[ADT123]

Thanks nbucska
Maybe you are right but i need to show the family why. They have many unanswered questions of which this is one.
If as you say sublimation is based on the surface
I know the blocks were approximately 230 x100 x 75 mm. If that helps

 

[IRstuff]

What was the driver using the dry ice for?
Did he have outside air vents open/closed?
A/C on/off?
Were the boxes stacked? open/closed?

TTFN

 

[TD2K]

Well, 150 kg of dry ice is 3.41 kgmoles of dry ice (MW = 44 kg/kgmole).

1 kgmole occupies 22.4 m3 at atmospheric pressure and 0C. At the temperature in the car, it would occupy about 10% more volume or 24.6 m3. 3.41 kgmoles would therefore occupy 84 cubic metres.

Now, as the C02 sublimated into vapor, it would have built up pressure in the van if it was air tight. The van wouldn't be air tight of course which would have resulted in some of the original air and sublimating CO2 to escape during this process. However, I can't estimate relatively how much of the air would have escaped versus the evaporated CO2 (the C02 would initially have been cold and would have sunk to the low points originally). However, given the volume in the van was only 3.72 m3 and air contains about 21% O2, it's easy to see how the oxygen content could have dropped below the 10% or so that is the minimum for life.

 

[ADT123]

Thanks IRstuff
What was the driver using the dry ice for?

The driver was taking cold food product packed in 10 cardboard boxes which were sealed by tape.
The boxes were 280 x 430 x 720 mm. Dry ice blocks were placed 2 each end 1 in middle.

They were stacked on top of each other (exact order unknown due to impact damage)
Did he have outside air vents open/closed?
Unknown due to impact damage, for this purpose closed

A/C on/off?
Unknown for this purpose even if on would have been recycled anyway

 

[IRstuff]

The plot thickens...

Given the variances in the responses and the uncertainty in the exact initial conditions, it might be quicker to simulate the accident with another set of boxes, dry ice and food and actually measure the amount of sublimation, which you can do by placing all the boxes on a scale.

27.8°C is not so warm that you would run A/C with full recirculation, particularly if the cargo was also generating a sizeable amount of cooling.

I think that at every turn, more questions come up.

Boxes wet/dry?
was temperature typical?
were the windows definitely rolled up/tight?

I'd go and do the experiment; it'll probably get you closest to the actual answer.

TTFN

 

[25362]

Some thoughts:

1. Sublimated cold carbon dioxide would bring down the temperature of 27.8^oC in a relatively small confined space in a matter of minutes.

2. Carbon dioxide toxic effects would be felt long before the oxygen concentration drops to dangerous asphyxiation levels by displacement. 6% CO2 in air would reduce the normal 20.9% oxygen level down to about 19.7%, hardly a dangerous limit from the oxygen depletion point of view.

3. Carbon dioxide (especially when cold) is heavier than air, thus it would tend to concentrate quicker at lower spots. Dangerous % could thus be attained in some areas over shorter sublimation periods than usual, especially without proper ventilation.

4. Lower atmospheric pressures, as those found at higher altitudes, accelerate sublimation. Higher pressures as in pressurized (by CO2 ?) compartments slow down sublimation.

 

[Guidoo]

The point of visibility has not been mentioned yet. From what I remember, there is a distinct mist/fog produced by sublimating CO2. This must have been noticed by the driver. Or maybe the accident was caused just because the driver couldn't see anything...

 

[25362]

If sufficient humidity is present to produce a fog, then consider the formation of carbonic acid by combining CO2 with H2O. This acid is eye irritating and could serve to give prior warning to the driver.

 

[Guidoo]

Just as an illustration, picture on following link shows how much fog can be produced by dry ice:

http://www.cobden.union.k12.il.us/Science web site/Bless/images/Archive/Phys sci 00-01/dry ice 2.jpg

Interesting link on the subject:

http://www.dryiceinfo.com/

This website explicitly warns against transporting dry ice in a car.

 

[nbucska]

As far investigation is concerned: It is obvious that so much CO2 is deadly -- this needs no investigation.
Evidently the driver didn't know about the danger. The
important question is &quot; WHY ?&quot;

Did he transport it for his own business of for someone else? Was this business/person responsible to warn/teach
the driver about the hazards of the job ? Did he know
how the CO2 was going to be transported? i.e. does someone
share the responsibility for the accident ?

I would rather investigate the history of the usage of CO2
-- source, if they supplied some warning, prior accidents,
experience, was the driver new in the job? etc.

<nbucska@pcperipherals.com>

 

[ADT123]

Thankyou to everyone who has responded thus far

25362 stated that fog would depend on Humidity. What sort of % are we looking at, and could the effects of carbonic acid in the mucus linings be felt prior to visual fog?

Can anyone suggest where I might be able to get further technical documents on CO2, with sublimation and fog and the formulas I need to try to determine some of these levels?


To nbucska
In response
Let me guarantee that the issues you have raise are very legitimate and are part of my investigation into this accident, some of the issues have already been addressed.

For me the concern that I need to seek advise on is in relation to sublimation of CO2. This may have a major impact as to how far the investigation can go. It will always be impossible to determine the exact cause of death and the circumstances around it due to the vehicle damage sustained in the accident. Therefore I need to determine the worst and best case scenario.

You are correct if all systems were put in place and applied prior to the driver driving he would still be alive today

I hope this puts your mind at rest that the investigation is not as narrow as it appears but is being presented in a way that is applicable to this forum.

Thanks again to everyone who has responded

 

[aviat]

These sites contain some info:

http://www.ntsb.gov/Recs/letters/2001/A01_14_15.pdf

http://www.airweb.faa.gov/Regulator...17862569ea00695c3c/$FILE/ATTPB60T/ac103-4.pdf

 

[IRstuff]

I would still recommend that you perform the experiment using as close a simulation of the actual situation as possible.

Any formula or other approach is open to challenge, since you cannot prove that the formulas specifically apply to the situation described. One can readily argue that the sealing of the boxes and the stacking severely limited the amount of sublimation and therefore was only a minor contributtor to the accident.

Actual measured data, using boxes, dry ice, sealing, stacking and temperature from the known facts should be significantly more robust and able to withstand challenge.

TTFN

 

[25362]

To ADT 123, FWIW you may visit

http://www.yeeha.org/enterhtml/live/lab/quality.html

it may give you ideas on where to look for help on your queries. Good luck.

 

[Montemayor]

ADT123:

You haven't stated WHAT killed the van's driver. If it was asphyxiation, you're onto something that points towards the CO2 level inside the van being excessive and maybe causing the driver's death. However, if the driver didn't suffer physical trauma or serious body wounds, then the CO2 issue becomes very &quot;iffy&quot; and debatable. Allow me to try to explain:

I have personal and extensive experience with continuous exposure to so-called &quot;high&quot; levels of CO2 and I can assure you from first-hand experience that the first thing(s) that a human being becomes aware of is the increasing level of asphyxia. It just doesn't happen from one second to the other. With CO2, it doesn't happen as it happens with CO (Carbon Monoxide). CO is toxic and poisons the victim by first rendering the subject unconsious. This is not what CO2 causes. A person exposed to continually increasing levels of CO2 in his breathing space will detect the effect as it starts and will identify a danger in proceeding to remain in the same confined environment - unless, of course, if he is unconsious from other effects (like a blow to the head) or constrained by a locked seat belt (both of which you haven't mentioned). Ammonia has a similar first effect on humans: it is detected almost immediately and with only a few ppms required. The immediate human reaction is a reflexive one: a mad rush to seek clean, fresh breathing air! Although the CO2 effect is similar to Ammonia's, it is much slower and not as accurate at the low concentrations - but nevertheless, it does yield a warning signal, albeit small.

I have stated this countless times before and I hate to repeat myself, but I'm afraid it's required again: CO2 is definitely NOT TOXIC! Carbon Monoxide, Ammonia, and Chlorine are definitely TOXIC - but not CO2. Any non-toxic gas like Nitrogen, Helium, or Argon will cause death by asphyxiation (much like CO2) if the victim is not allowed a fresh supply of breathing air. Properly designed ventilation is always one of the top priorities that one must design for and have available where human beings are involved. In fact, one of the key positive features of CO2 vapors generated by Dry Ice sublimation is the fact that, as 25362 has accurately pointed out, the -109 oF vapor causes a distinct and clearly visible WHITE FOG. This fog is nothing more than atmospheric water moisture that is condensed at the -109 oF temperature and is no more &quot;toxic&quot; than the CO2 vapor. This white mist is so ordinary that it is commonly used in &quot;spooky&quot; films, TV programs, Halloween apple bobings, Rock & Roll Concerts (in closed, un-monitored auditoriums!) and many other entertainment events. My point here is that it is a clear indication of the existance of cold CO2 in the immediate environment to a potential victim who should heed the warning. No such indication occurs in the case of N2, He, & Ar. As everyone on this forum must be aware, CO2 fire extinguishers are a &quot;dime a dozen&quot; and found literally everywhere. Yet, no special breathing apparatus or precautions are demanded of its use - other than common horse sense in furnishing proper ventilation. I would be so bold as to assert that a CO2 fire extinguisher was probably in the van! And does anyone question or suspect that? (The white fog seen in the discharge of a CO2 fire extinguisher is EXACTLY the same effect as the sublimation of Dry Ice.)

Sublimation rates depend on a variety of factors, as appropriately noted by some of the above respondents to this thread. Without accurate and definite information on the existing ventilation, temperature, van conditions, victim's awareness, etc, one cannot even make a credible estimate or approximation of the amount of CO2 that would have sublimed within the available time. The sublimation rate is a horse-sensical matter: the more available heat sink that is brought in contact with the Dry Ice, the faster the sublimation rate! Paradoxically, as the Dry Ice sublimes, it forms it's own very effective cap of insulation and protection: the sublimed CO2 vapor!! Unless mechanical or convection currects are induced or produced, the sublimation rate falls rather than increases!

Another item: was the victim upright? As 25362 again points out, the heavier CO2 will precipitate to the lowest region in the van (if the van is almost hermetically closed, without any outside ventilation - of which we know nothing) and give the victim more time to take action or make a decision. Again, I stress the fact that the victim will not black out; if constrained and forced to breath heavier doses of CO2, he would get progressively weaker and weaker - but he would be aware of it.

I heartily agree with IRstuff in that the real, positive proof that CO2 could have asphyxiated the victim is to simulate the accident with an identical van, Dry Ice shipment, conditions, etc. As far as generating any positive help on that determination via the use of sublimation equations (none exist, I can assure you), I believe that is too difficulat due to the scarcity of the basic data given on the incident.

Right at this moment there are perhaps hundreds of tractors pulling semitrailers loaded with tons upon tons of Dry Ice throughout our country on a daily basis. There is no ventilation used in the trailer and the driver uses a forklift to remove the many large crates of boxed and wrapped Dry Ice. The driver actually goes into the parked trailer and removes each crate, working his way to the rear-most section of the trailer - of course, the trailer is open at this time. My point is that on an empirical and experienced basis, there are many people (beside myself) who can easily testify as expert witnesses (I already have in the past) to the fact that working with, transporting, and handling Dry Ice is not a dangerous nor toxic operation per se. This does not discount the possiblility that in your case the victim was asphyxiated with CO2. However, wouldn't a coroner's report bear this out?

I hope I have not added confusion to the problem, but rather that I succeeded in clearing some items up. I have always believed in keeping the potential dangers of all gases clearly focused and always in our engineering safety awareness. No gas (or chemical) is so benign that it can be discarded as a potential danger - and CO2 is no exception. I wish you success in your investigation.

Art Montemayor
Spring, TX

 

[JOM]

Art,

That's a helpful explanation. I'll admit that I've been thinking in simple terms of:

inert gas + confined space + person = fatality.

The important thing you're telling us is the person will sense that something is wrong and seek fresh air. H2S and chlorine alert us to their presence, but nitrogen and CO do not.





Cheers,
John.

 

[25362]

As I see it, ADT123 never even insinuated that the cause of the accident, let alone the driver's death, was dry ice sublimation, he/she is just investigating the various possibilities.

I'm inclined to follow Art Montemayor's message, and discard any &quot;a priori&quot; blaming of the dry ice sublimation. I believe that a variety of other factors such as human sleepiness, or the driver's brief distraction, not to mention a temporary sickness, and mechanical failures, or even external causes such as an animal crossing in front of the van, may have been the contributing factors to this largely undefined &quot;one-car&quot; accident.

There are plenty of possible/probable causes that an expert in car accidents would have to sort out before a final answer can be given.

 

[chicopee]

Any toxicology test done on the deceased driver?