From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: rec.pyrotechnics
Subject: Re: Question
Date: 11 Jan 1996 20:22:54 GMT

In article <821201038snz@firework.demon.co.uk>, Andy Hubble
<Andy@firework.demon.co.uk> says:

>In article <4d1srq$vl0@tetsuo.communique.net> helper@communique,net "Me"
>writes:
>
>> Is there a way to safely detonate a can of hairspray to make it explode?  
>
>Sounds extremely dangerous to me. Having an aerosol can explode whilst
>you are nearby can have grave consequences.
>
>I'll never forget a photograph I was shown by the local Fire Brigade of
>the aftermath of a childrens' game that went wrong. A few children were
>out playing on the local village green, using aerosol cans of hairspray
>as flame throwers. Unfortunately, when one of them released the pressure
>nozzle at the top to stop the flame, the flame travelled back into the
>can, igniting the contents whilst the can was still in the childs hand
>and causing a huge explosion.
>
>The next bit is gruesome - don't read it if you're easily offended. All
>that remained of the 11 year old childs corpse was his left arm, half
>of his main torso and both legs. Everything above a diagonal line 
>running from his left shoulder down to his right hip had disintegrated 
>in the explosion. His head, right arm and part of his main torso were
>completely unrecognisable in the piles of smoking remains.
>
>Seeing that photograph has deeply affected me. Playing with aerosols and
>fire is like playing Russian Roulette. Anyone that wants to make one
>of these things explode, "safely" or not, needs their head examining.

Andy, the amount of bodily destruction you describe is far greater
than anything the contents of an aerosol can could possibly inflict.
It would take a sizable solid or liquid explosive charge such as
dynamite sticks to "disintegrate" a torso.

Jerry (Ico)

From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: rec.pyrotechnics
Subject: Re: Question
Date: 12 Jan 1996 20:53:32 GMT

In article <821427889snz@firework.demon.co.uk>, Andy Hubble
<Andy@firework.demon.co.uk> says:

>If you were suggesting I was lying, then of course I'd take offence. I'll
>take your word that an exploding aerosol would not cause this damage,
>but in my opinion the photograph was genuine (it's pretty hard to fake
>such an appalling injury without spending stacks of cash isn't it?) and
>I can't think of any reason why a *fire officer* would want to BS to me.
>Anyhow, enough said, I saw the photo and I can't say anymore than what 
>I've already written. I must admit I have problems understanding how a
>flame could go back down the nozzle! 

Andy, let me apply my experience as a fire and explosion analyst
to this question. I can obviously only speculate on the facts, but
I have seen many many explosions misinterpreted by the 
investigating authorities. Much of my work involves disproving
poor cause-and-origin attributions by investigators. I would
GUESS that the poor victim was killed by a fullblown explosion
from a conventional source such as a home-made bomb. The fire
officer probably really believed or wanted to believe that the
origin was an aerosol can.

I know that it will sound ridiculous to many to hear me say that
a professional could make such a clearly obvious mistake, but
believe me when I opine that this is a common occurrence.

Jerry (Ico)

From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: rec.pyrotechnics
Subject: Re: Question
Date: 12 Jan 1996 20:39:23 GMT

In article <4d4avr$qsq@sundog.tiac.net>, ohearn@tiac.net (Dave O'Hearn) says:

>Gerald L. Hurst (glhurst@onr.com) wrote:
>
>: The next bit is gruesome - don't read it if you're easily offended. All
>: that remained of the 11 year old childs corpse was his left arm, half
>: of his main torso and both legs. Everything above a diagonal line 
>: running from his left shoulder down to his right hip had disintegrated 
>: in the explosion. His head, right arm and part of his main torso were
>: completely unrecognisable in the piles of smoking remains.
>
>This is a classic style of hoax. Either you're lying, or you fell for the
>lie yourself. 

That's pretty strong language, especially since I did not write 
the post you have quoted.  Many people will not notice the double
punctuation (>:) indicating that the paragraph was being quoted
by me in a post which strongly disagreed with the content of that
paragraph.

Later, you ask if a flame could flash back into an aerosol can. 
Probably not except in very extraordinary circumstances, because
it would be difficult to imagine a scenario that would allow 
enough air to flow back in to yield a combustible mixture. If
the valve were to stick open, diffusion and thermal cycling might
eventually result in the formation of a flammable mixture, but
there is little chance that a flame could pass unquenched through
the tiny valve orifice. Also, it would not be surprising if an
aerosol can were to withstand the rather anaemic pressure of a
small quantity of FAX. You could expect much higher pressure from 
the highly dangerous act of overheating a normal can.

I am assuming, of course, that the can uses some conventional
hydrocarbon propellant or contains some flammable liquid with
a suitable flash point. There are, of course gases which might
explode, but are unlikely to be found in aerosol containers.
Examples would be acetylene or some flammable mixture inadvisedly
using N2O as a propellant for something other than whipped cream.

Jerry (Ico)

From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: rec.pyrotechnics
Subject: Re: Question
Date: 13 Jan 1996 19:35:38 GMT

In article <380@heathreach.win-uk.net>, geraint@heathreach.win-uk.net
(geraint evans) says:

>>It certainly didn't slice his body in two. I find this, frankly,
>>inconceivable for a household aerosol of hairspray.
>
>You obviously didn't see the picture in our press of what an
>overheated aerosol can did to a house!!!! If it can wreck a house I
>can appreciate Mr Hubble's concern.

No, we probably didn't. Why don't you describe the damage to us
to see if it appears that the destruction is indicative of
the level of destructiveness required to disintegrate a human
torso.

Jerry (Ico)

From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: rec.pyrotechnics
Subject: Re: Aerosol Can Explosions
Date: 13 Jan 1996 23:16:03 GMT

In article <4d9cc7$r34@ns2.ptd.net>, xopher@ptd.net (xopher) says:

>I was told that someone dropped a can of hairspray that had been
>outside in below-freezing weather...and it went BOOM

This is conceivable if it was a water base liquid using CO2
(or less likely N20). Both of these gases are soluble in 
liquid water but not in ice. If you have a container with
very limited hullage, as in a bottle of cola, the gas 
pressure can get very high if the contents freeze.

Jerry (Ico)

From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: rec.pyrotechnics
Subject: Re: Question
Date: 16 Jan 1996 04:51:21 GMT

In article <30FAD8A1.5A78@winternet.com>, bigfoot <bigfoot@winternet.com>
says:

>Gerald L. Hurst wrote:
>
>> Andy, the amount of bodily destruction you describe is far greater
>> than anything the contents of an aerosol can could possibly inflict.
>> It would take a sizable solid or liquid explosive charge such as
>> dynamite sticks to "disintegrate" a torso.
>
>If the very most WRONG things were to happen I think it could. The can 
>would have to burst, atomizing the fuel and then it would have to be 
>ignited by a seperate event. Thus the fuel/air bomb is born, the single 
>most powerful non-nuclear explosive in the US arsenal.

Only in your dreams :) The problem of creating the necessary dispersed
little cloud of typical can fuel and then initiating a detonation
therein would be a very uncertain undertaking even in with
the resources of an explosives laboratory.  In the very remote 
event that it did happen, the detonation pressure would still
not be enough to disintegrate a torso. Large FA explosions 
generate enough overpressure to kill but not destroy a human
body. They are effective against structures because a few tens of 
psi over large wall areas will shatter even a reinforced building.
Ordinary buildings cannot structurally withstand more than a
few psi.

Jerry (Ico)

From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: rec.pyrotechnics
Subject: Re: Aerosol Can Explosions
Date: 16 Jan 1996 04:56:55 GMT

In article <BILLW.96Jan15185225@puli.cisco.com>, billw@puli.cisco.com
(William ) says:

>Yep.  I've (accidentally) exploded cans of soda both by heat (in the trunk
>of my car) and by cold (you start by trying to get a can cold in a hurry by
>putting it in the freezer, and then you forget about it.)
>
>Makes a real mess.  You can reduce the amount of mess somewhat by using
>diet soda instead of those containing (sticky) sugar!

Genius that I am, while I was writing on this theme my daughter
asked me "How long have those Cokes been in the freezer?" I
snatched them out in the nick. One had ballooned the bottom.
The last time, I was not so lucky except that, as you say, it
was a can of diet drink :->

Jerry (Ico)

From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: rec.pyrotechnics
Subject: Re: Question
Date: 17 Jan 1996 04:17:07 GMT

In article <384@heathreach.win-uk.net>, geraint@heathreach.win-uk.net (geraint evans) says:

>In article <4d91ia$74d@geraldo.cc.utexas.edu>, Gerald L. Hurst (glhurst@onr.com) writes:
>>In article <380@heathreach.win-uk.net>, geraint@heathreach.win-uk.net (geraint evans) says:
>>
>>>>It certainly didn't slice his body in two. I find this, frankly,
>>>>inconceivable for a household aerosol of hairspray.
>>>>
>>>
>>>You obviously didn't see the picture in our press of what an
>>>overheated aerosol can did to a house!!!! If it can wreck a house I
>>>can appreciate Mr Hubble's concern.
>>>
>>No, we probably didn't. Why don't you describe the damage to us
>>to see if it appears that the destruction is indicative of
>>the level of destructiveness required to disintegrate a human
>>torso.
>>
>>Jerry (Ico)
>
>
>Room trased, windows blown out (inc frame), damage to celing roof
>etc. Also other cases where can has fallen on a fire and
>demolished brick fireplaces. Basically, if it will damage the
>fabric of a house then there is the possibility of Andy's
>description, just don't dismiss it out of hand.
>
>Also there have been good points raised about non-standard
>fillings of the can which could explain a lot.
>
>The flame needn't flow down the nozzel, a flare up on the top could
>melt the seal between the two parts of the top causing a blowout,
>followed by a FAE. The can propelled backwards could do a lot of
>damage.
>
>But still, we are ALL speculating as we have no further
>details or evidence. My favourite explanation is it may have been
>refilled with a chlorate mix and the description of the incident
>may have been wrong. 

Obviously we don't know that someone didn't use an old aerosol
can as a bomb casing. If that were the case, the original 
contents of the can would be of only incidental interest.

However, I, and presumably others, are not speculating about
the inability of a can of hairspray or the like to disintegrate
a torso. It can't.

Your example of blowing windows out or raising the roof with
the FA explosion from the contents of a spray can is nothing
unexpected and has nothing to do with the idea of fuel/air
detonations. A few ounces of hydrocarbon fuel dispersed in
a room is more than enough to account for such damage without
invoking anything more exotic than a simple deflagration. You
simply need the contents of the can to escape without burning,
either disperse as a mist or evaporate and disperse by 
diffusion and then find an ignition source. The combustion 
can take place over a period of a second or so, which is
too fast for venting and, voila, the walls and roof move
and windows blow out.

This sort of thing happens all the time with natural gas and
gasoline as the most frequent culprits. I have handled 
several cases of this sort over the last few years and am 
working on a couple more right now.  The last wall-moving 
deflagration involved an estimated amount of about 30 grams 
of methane in a bathroom. The flash only burned the occupant
of the bathroom rather badly on one shoulder and that side
of his back. A similar explosion, again by methane in a 
bathroom. blew a lady off the commode but burned her so
badly both externally and in the lunge that her life will
be one of unceasing pain. In the latter accident, three
walls and a roof were moved and fire damage was extensive.

A much larger explosion occurred in a new car storage garage
which filled with gas following the rupture of a line. The
explosive shock form the sudden rupture of the large
windows and front wall was so intense that a major hotel
across the street and over the hotel plaza suffered heavy
damage. The estimated pressure at the hotel was no more than
a few psi at most, but the damage was extensive.

Jerry (Ico)