From: John De Armond
Newsgroups: rec.outdoors.camping
Subject: Re: Heat sources in a Winter Camp tent
Date: Wed, 13 Sep 2000 14:26:30 -0400

BobbyG wrote:

> Are there any safe propane heat sources that can be used in a
> conventional tent in the winter camp environment?  Or do they all
> produce unacceptable CO (carbon monoxide) buildup?
>
> In the past I always just suffered the cold rather than trying to heat
> the tent.  Now as a Married Man living the Great American Suburban Life
> (capital letters intentional), I find that what I would tolerate and
> what my dear spouse would tolerate are
>
> (radically)
>
> different.

:-)

Instead of guessing, why not carry a small portable carbon monoxide
detector to be sure?

The new Coleman propane fired catalytic heater can be used indoors.
It's a nice little portable rig that screws on a propane tank and
emits most of its heat as infrared radiant heat.  We find it very
nice to hang from a string aiming toward us as we cuddle up under a
blanket to watch TV or whatever.  It's available from Wallyworld for
about $35.

John

From: John De Armond
Newsgroups: rec.outdoors.camping
Subject: Re: Heat sources in a Winter Camp tent
Date: Wed, 13 Sep 2000 20:56:22 -0400

"Lou W." wrote:

>     Not to contradict your idea John, but.............A decent
> bag will do the job without the risks of a propane heater.

I'm not sure there are any risks worth considering with the
catalytic heater.  The chemical reaction (not combustion) takes
place deep in the catalyst pad and produces only CO2 and water
unless the heater is absolutely starved for air.  One can see a very
dull glow down inside the pad.  It does not make enough heat to burn
things that touch the guard under normal conditions.  If you drape a
sleeping bag across the burner, it will probably at least smoke the
thing, of course, but I find that I don't have to be very careful at
all about placing this heater near things.

My main use for the heater is in my tiny motorhome. I like using it
while watching TV because it doesn't make fan noise like the furnace
does.  I have a NightHawk CO monitor in the rig that has a digital
readout.  The little heater never bumps this thing off of zero,
something I can't say for the cook stove.  Being an experimentalist
and having the equipment, I have sniffed the air in the RV with my
MSA laboratory NDIR CO analyzer.  CO was below the minimum
detectable after several hours of the heater operating with no
explicit opening.  Gives me confidence in both the Nighthawk and the
heater.  That's nice since we sometimes drop off to sleep while
watching the tube.

We also sometimes pitch a tent outside so that we can enjoy the fall
or spring weather outside the RV box.  The little heater excels
here.  hang the sucker on a string from the tent ceiling, let it
radiate toward your feet and all is well in paradise without having
to do the Eskimo imitation.

I personally don't like to have to bundle up with nothing showing
but my nose tip.  That was fun when I was younger but at my age,
both me and my arthritis want heat!!  I still carry a little CO
detector and use it in the tent.  Typical of engineers, I abhor open
loop designs (also called hope'n'pray) and want to close the loop
with a little feedback.

Besides, if his wife is like MY wife and I came up with the
suggestion to just "bundle up" in response to the cold, she'd say
"Have a nice trip, dear."  Not really into that solitude thing
anymore :-)

John

From: John De Armond
Newsgroups: rec.outdoors.camping
Subject: Re: Heat sources in a Winter Camp tent
Date: Thu, 14 Sep 2000 05:23:19 -0400

BobbyG wrote:

> Ah, I should have read on further before I replied first time.  This
> "Nighthawk," is that the portable CO detector you first mentioned?  Is
> it battery powered or AC?  The "MSA Laboratory NDIR CO Analyzer" just
> sounds expensive, just by the name of it, and I'm guessing is NOT
> available at Wallyworld.

The nighthawk is line operated and is what I have installed
permanently in my RV.  I understand that they now have a battery
powered version but I don't have it.  My little portable rig, a
combo ionization fire and CO detector is one that I got before I got
the motorhome. Wallyworld special, if I recall, probably a First
Alert. I carried it in my travel bag for use in motel rooms.  I've
crawled out of one burning bedroom with little more than my life -
never again if I can help it.

The Non-Dispersive InfraRed analyzer is indeed expensive - around
$5k for the model I have.  I acquired it (used, MUCH cheaper than
that!) for use while doing electronic engine management development
work. I actually have two of these instruments - one is calibrated
to CO and the other to CO2.  Being prone to hang test equipment off
of anything within my reach, I just had to check it out :-)  Knowing
that this heater used about the same catalyst makeup as a cat
converter on a car, I just wanted to see if it was as efficient.  It
is.  BTW, a car cat converter makes a wonderful heater and has a
flue connection to boot!  Just pipe in some gas and air and light
the cat off with a propane torch and enjoy.  I used a homemade
heater of this sort in my shop for years.  You can get the whole can
glowing red hot without overheating the cat if you're careful.

From: John De Armond
Newsgroups: rec.outdoors.camping
Subject: Re: Heat sources in a Winter Camp tent
Date: Thu, 14 Sep 2000 05:31:06 -0400

BobbyG wrote:

> Neon John wrote:
>
> Instead of guessing, why not carry a small portable carbon monoxide
> detector to be sure?
>
> --Where have you seen these?  I'm interested.  All the ones I've seen have
> been AC-powered, not portable. I will have one plugged in near the wood stove
> in my basement this winter, but as I said, it's AC, not portable.

Walmart, AKA "Wallyworld."  Mine's a combo smoke and CO detector.
Very sensitive.  Runs on a 9 volt battery.  Probably a First Alert,
though I'd have to walk out to the motorhome to be sure.

> The new Coleman propane fired catalytic heater can be used indoors.
> It's a nice little portable rig that screws on a propane tank and
> emits most of its heat as infrared radiant heat.  We find it very
> nice to hang from a string aiming toward us as we cuddle up under a
> blanket to watch TV or whatever.  It's available from Wallyworld for
> about $35.
>
> --I take it that the "catalytic" feature reduces the CO danger, but of course
> the fire danger remains as other posters have mentioned.  And "Wallyworld?"
> Is that Wal-Mart? (Pardon my ignorance...)

The fire danger is GREATLY reduced because there is no flame.  The
chemical reaction runs at about 900 degrees if my memory serves.
Still possible to kindle a fire under the right conditions, of
course, but not nearly as likely as with an open flame.

John

From: John De Armond
Newsgroups: rec.outdoors.camping
Subject: Re: Coleman Powercat Heater:  Why only Propane 16 oz cylinder
Date: Fri, 27 Jul 2001 04:16:18 -0400

cannga wrote:

> I just bought a Coleman Powercat Catalytic Heater.  The instruction says:
>
> "Use 16.4 oz. (465 g) cylinders only.  Do not connect to bulk propane
> systems."
>
> Does this mean I could not use this heater with the 20 lb size Propane tank
> (using extension with tank outside of tent)?  If so, does anyone have an
> explanation please?

Well, since Coleman chose not to hire me to design the thing, I'm
just going to have to SWAG it. :-)  There is no difference in
performance because the gas is essentially the same.  In this
sue-happy world, I imagine the main concern is physical stability.
The tank servers as one leg.  With a bulk tank hose screwed up in
there, there is nothing secure to rest on, only a floppy hose.  I'm
sure the lawyers forced that clause in the instructions just to
cover their butts.

A secondary issue might be gas purity.  Bulk propane tends to be
fairly contaminated, usually with water but also sometimes with
tramp oil and misc mung.  The propane in the torch cylinders is much
more tightly controlled because of the tiny orifice in the main
target - the propane torch.  Contamination could cause the thing to
go out, to flare up or even contaminate the catalyst and make it
quit working.

A final consideration might be that attaching it to plumbing might
put it under the part of the gas code that requires pilot safeties,
O2 depletion sensors and the like.  All this stuff is required of
unvented indoor gas appliances.  That you'd have to be living in a
garbage bag for the tiny bit of air consumption involved to deplete
the oxygen but them's the rules. They don't have to be rational.

John

From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: Ventless propane heaters?
Message-ID: <gt91pu0elidnbovmp5rbn00g1qq3lg7cq6@4ax.com>
Date: Tue, 24 Sep 2002 14:05:56 -0400

On Mon, 23 Sep 2002 09:22:27 -0400, "Scott Bershing" <bersh@chartermi.net>
wrote:

>Is there a reason why one of the ventless propane heaters can't be used in
>an RV?

I use one of the Coleman BlackCat portable catalytic heaters as supplemental
heat in my small rig.  This unit takes throw away cylinders but I have a high
pressure hose plumbed to the ICC tank to fuel it.  It works wonderfully to
take the chill off or to keep my feet warm when I don't need any other heat.
Also got me through a very cold snowstorm when my regular furnace went on
strike.

To address the inevitable bleats of the safety nazis...  this heater makes no
carbon monoxide, as would be expected from a catalytic heater.  I have a
NightHawk CO monitor with the digital display.  The indication never gets off
zero with the heater.  Heating a pot of water on the stove for coffee, on the
other hand, produces a reading of from 20 to 25 ppm CO for a short period.

Regarding fire hazards, while I would not recommend this as a practice, I did
test mine by laying some paper on the protective grid.  It charred and smoked
but did not catch on fire.

The built-in catalytic heaters made for RV use work the same way.

These heaters do use oxygen but unless your rig is airtight this isn't a
concern.  I could only dream of my rig being that tight!  If you really like
to worry I suppose you could install an oxygen monitor too.

John

From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: Ventless propane heaters?
Message-ID: <bev6pu4scvstleffldm2m8colf814civst@4ax.com>
Date: Thu, 26 Sep 2002 17:40:33 -0400

On Thu, 26 Sep 2002 12:05:39 -0500, in rec.outdoors.rv-travel you wrote:

> In the Plaque type, the same thing is
>done but without a catalyst and therefore combustion occurs at a higher
>temperature. This is the one feature of the plaque heater that I enjoy. It
>is a powerful radiant heat source, and the pleasure of baring ones derrière
>to such a source on a cold morning cannot be described adequately. I suspect
>that 600 DegF would not be quite the same.

You would be wrong.  I have both.  The catalyst blanket acts as an almost
perfect black body radiator.  It glows a very dull red, visible in a dark
room.  It radiates a LOT of heat.  The difference between the surface
combustion heater and the catalytic heater is that your distance isn't so
critical.  A little too close with the surface combustion heater and your
derriere is flambe'.  The catalytic heater is much less critical in that
regard.


>    Many years ago it was found that the use of a vanadium compound
>increased the efficiency of gas turbine combustion and hence the nasties in
>the exhaust. However the public health people got all shook up, and probably
>rightly too, about the release of vanadium into the atmosphere, so it was
>never widely used. What about the catalyst release? I don't think the
>platinum is there as a pure element and probably has a carrier itself, which
>might vary from one manufacturer to another.

The platinum is there in elemental form.  Considering its nobility it would be
fairly difficult to have it any other way.  It's typically applied as a very
dilute solution of platinic acid (sp) that is then fired.  The firing reduces
the platinic acid to elemental platinum.  There are only a few mg across the
whole heater element.  If the platinum goes away the heater quits working.

>That is where I can see the
>possibility of some adverse effects.

Like what?  Platinum is almost totally inert and is one of the few
biocompatible metals that can be implanted in the body.  Hope you didn't
blister your hands while wringing them...

If I were going to worry about anything about a catalytic or surface burner
heater (and I'm not) I'd worry about the substrate subliming and emitting
micron sized particles of silicon dioxide.  You know that white deposit that
plates out above a surface burner?  Guess what that is?

John

From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: Programable thermostat for trailer
Message-ID: <4snhru0sj1efk55gidtstp9b4porvchcb4@4ax.com>
Date: Fri, 25 Oct 2002 02:22:14 -0400

On Thu, 24 Oct 2002 15:24:01 -0700, "Mark" <mark9934@hotmail.com> wrote:

>Is anybody aware of a programable thermostat for an HVAC system in a
>trailer?
>
>We have a 2002 Nash TT with a coleman Mach 3 AC and a suburban FAU.  It
>would sure be nice to add a programable stat just like at home.

Sure.  Any of the digital 'stats that are battery powered, as opposed to loop
powered, maybe with a battery backup, will work.

The particular one I have is a Hunter Model 42345 Energy Saver Deluxe.  Got it
from one of the Big Box outfits.  Among the features I like is the very tight
1 deg deadband.  The room temperature varies only slightly.

I have this same 'stat in my apartment.  On the AC side, it controls a
conventional central AC.  On the heat side, it controls a floor standing 240
volt convection heater that I modified by adding a contactor and transformer.
Two totally independent units, just like in an RV.

I have mixed emotions about this unit in the RV.  I like the auto setback
feature and the precision.  But I don't like having to sit up in bed to adjust
it.  You have to hold the up or down arrow button for a couple of seconds
before it starts working and then the temperature setpoint changes rapidly.
Looking at it is a must.  With the old mechanical 'stat I could just reach up
and turn it until the unit kicked on.  I have yet to find one that has a
mechanical-like temperature set AND is battery powered AND can control two
separate units.

Changing the subject a bit, Sam's now has the very good NightHawk digital CO
monitor at a very good price. About $24 as I recall. This is the rectangular
unit with the digital display in the center and a large "N" cutout for the
sound to escape.  This is a superb unit for an RV.  It is line powered and
battery backed.  It has a small wall wart in the back that can be removed so
the monitor can be located away from an outlet.

After analyzing the internal circuit, I discovered that I could simply cut the
wall wart off and connect 12 volt house power directly to the leads - polarity
doesn't matter.  The 9 volt battery must still be there for normal operation
which is good since it provides a backup to the RV power.  The power draw is
very low - just a few MA.

I got one of these the last time Sam's had them and have had it installed in
my rig for about 6 months.  It works wonderfully.  By UL code it can't display
any CO reading less than 100 PPM but it WILL display the peak value since last
reset if you push the front panel button.  I know, for example, that running
the stove long enough to make a pot of coffee generates about 25 PPM CO even
with the hood fan on. Running the genny all night in a wal-mart parking lot
with the AC on results in about 45 PPM. I also know that my Black Cat portable
catalytic propane heater generates zero CO.

John

From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: Programable thermostat for trailer
Message-ID: <boviru873mjd0lql9bldadrhm5ud6d0vag@4ax.com>
Date: Fri, 25 Oct 2002 13:39:17 -0400

On 25 Oct 2002 08:48:21 -0700, sbourg@hotmail.com (S. Bourg) wrote:

>> I got one of these the last time Sam's had them and have had it installed in
>> my rig for about 6 months.  It works wonderfully.  By UL code it can't display
>> any CO reading less than 100 PPM but it WILL display the peak value since last
>> reset if you push the front panel button.  I know, for example, that running
>> the stove long enough to make a pot of coffee generates about 25 PPM CO even
>> with the hood fan on. Running the genny all night in a wal-mart parking lot
>> with the AC on results in about 45 PPM. I also know that my Black Cat portable
>> catalytic propane heater generates zero CO.
>
>Well, I 'know' your Black Cat does NOT produce 'zero CO', since there
>is nothing magic about the chemistry. This is the real danger with
>believing what you read instead of what your logic will tell you.
>
>Our Olympian model will produce enough CO to register 0.6 ppm in a
>laboratory test under controlled conditions, which says little except
>that the amount produced is small and not below the resolution
>threshold of THAT test equipment. Still, it validates the theory.
>
>It would be easy for a confused individual to take a zero reading on
>their cheap meter to rationalize shutting down the vents on a cold
>night - or to interpret your 'results' as equivalent justification.

*Sigh* I forgot that there's always some drizzling dipshit nipping at anyone's
heals who makes a useful post.

My Black cat is NOT your olympian and I'm NOT reading off some generic spec
sheet.  Had I remembered where I was posting and the sort of characters
inhabit this group, I would probably have elaborated that my 4 gas analyzer
with a resolution of 0.001 ppm CO (though not that accurate) ALSO registers
0.000 ppm when sniffing the plume above the heater.  That shouldn't be
surprising since modern automotive engines also typically register 0.000 ppm
CO under steady state cruise conditions.  That's typical of a deep catalyst
bed which both a car catalytic converter and the Black Cat are. If I thought
anyone would have cared, I'd have mentioned that the Nighthawk reads exactly
10 (no decimal) ppm when exposed to the analyzer's 10 ppm cal gas.

I suppose I could mass spec the thing (yes I have one of those too.) but
frankly I don't give a flying f**k and I doubt that anyone else does either.

What matters is that I do not have to worry, and in practice don't, about the
emissions of this heater.  My rig is not air tight enough to allow any buildup
even with all the windows and doors shut.  If I were to buy an Olympian, I'd
test that particular unit before relying on it.

John, who remembers again why he hasn't been contributing much to this group
lately.

From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: Programable thermostat for trailer
Message-ID: <heimru8n87qlhkck5sllmdjaao6t8ss4c7@4ax.com>
Date: Sat, 26 Oct 2002 22:12:58 -0400

On Sat, 26 Oct 2002 19:25:28 -0400, GaryO <> wrote:


>John,
>
>I'm curious about your Black Cat unit.  I've seen these in the stores,
>and have thought about using one in the RV - looks like it would be no
>problem from your testing.  Can you tell me if you are using this with
>the disposable cylinders, or do you have it plumbed-in?  If the
>disposable cylinders, how long do they generally last?

I use it both ways, depending on the situation.  I keep several cylinders in
the rig.  When I get caught needing to take just a little chill off I fire it
up with a disposable cylinder.  I also have a high pressure hookup.  When my
furnace went down on a long trip last Christmas I used this heater instead of
trying to fix the furnace out on the road.    I also have a hookup outside so
I can sit outside when it gets a little chilly.  Finally, I have a 5 lb
portable tank (Northern Tool) for when I'm going to be a ways from the rig.

I'm not really sure of the life of a disposable.  When I'm demanding max
output the disposable tank fairly quickly frosts up so I swap between several.
I top 'em all off when I get home.  I would imagine a disposable tank would
last all night at the regular setting.

The heater doesn't put out all that much heat stock, about 7000 btu I think.
It has an extra high setting for lighting the thing.  That position is
spring-loaded.  I made up a little bracket to clamp the knob in the "start"
position.  I'm going to SWAG it and say it puts out twice the normal heat.
The catalyst bed glows fairly brightly at this setting.

Note that I have NOT tested the CO output in the supercharged setting.  I've
never needed to operate it like that indoors.  I use that position when I'm
outside.  I'll probably find out this winter.

John

From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: "Space Heater" question
Date: Wed, 11 Feb 2004 22:04:51 -0500
Message-ID: <rqql20ldhnvqtkp5c5rb6e7lqp55bhvcug@4ax.com>

On Wed, 11 Feb 2004 17:37:08 -0800, "Dave Thompson" <davethompson@cmeforit.us>
wrote:


>Yes, there is a difference - the temperature at which combustion takes
>place.  If you dream and hope that a catalytic heater will never produce CO,
>you are whistling by the grave yard.  One day the goblins will leap out and
>bite you.

Lots more complicated than just the difference in temperature.  The whole
chain of intermittent products is different in the presence of the catalyst.
For reasons involving some reaction kinetics that I'm not sure I fully
understand, the production of CO on a catalytic bed is quite difficult.

I've experimented some with one of my Black Cats, experiment involving putting
the Black Cat and a CO monitor in a large box and then choking down the air.
What I've seen so far as I slowly smother the heater is a decrease in heat and
CO2, an increase in free hydrocarbons and zero CO.  My SWAG theory is that as
the oxygen level decreases, fewer and fewer reaction sites remain hot enough
to work.  Those sites below the temperature threshold of reaction simply do
nothing - the propane and depleted air simply pass by the sites.  That's my
SWAG.  I'm not interested enough to experiment any more.

That said, IMHO anyone who sleeps with a non-vented fuel appliance of any sort
without having an indicating CO alarm such as the NightHawk on guard is
foolishly tempting fate.  So far I have NEVER seen my NightHawk budge off of
zero when the Black Cat is heating exclusively.  Still, the NightHawk is
always on.

John

From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: ever take apart a "Buddy Heater"?
Date: Sat, 02 Sep 2006 23:32:54 -0400
Message-ID: <1ohkf2hboib15ht734m68l7kg2uodmve3s@4ax.com>

On Sat, 02 Sep 2006 19:57:03 -0600, boondocky@no.spam wrote:

>"Technobarbarian" <Technobarbarian-ztopzpam@gmail.com> wrote:
>
>>
>><boondocky@no.spam> wrote in message
>>news:1qlhf2tergcad39apdl0isbu8ufk5gv0aq@4ax.com...
>>>I heard someplace that they're a type of gravity heater.  Anybody know
>>> what's inside the things?
>>
>>      Looks like a pretty standard catalytic heater to me. As I understand
>>the phrase "gravity heater" it refers to a gas appliance that has the
>>exhaust gas vented to the outside and it can be operated without
>>electricity. In a "gravity heater" made for an RV "sealed combustion" is
>>used, so that the air supply for the burner also comes from the outside.
>>
>>     Looks like you've already seen this too:
>>http://www.mrheater.com/productdetail.asp?id=784&cid=164
>>
>>TB
>
>Dunno TB, I got the impression that it wasn't catalytic, that it just
>heats this grid thingy which radiates.  I used to have a Pelonis
>(electric) that seemed to work that way.

You're correct and TB is wrong.  It uses what is known as a ceramic
surface burner.  A tiny flame burns over each hole in the ceramic
burner.  The flame is so tight and so close to the ceramic that it
heats the ceramic red hot and the ceramic in turn radiates heat.

I have a Buddy but I don't like to use it in my RV.  With the open
flame it is possible to heat something that falls against it hot
enough to catch on fire.  I much prefer my Black Cat catalytic heater
when, for whatever reason, I don't want to use my furnace.  The
catalytic reaction is cool enough that even a piece of paper laid on
the surface of the thing barely browns a bit and will not get hot
enough to smoke.

To answer another question in this thread, the "oxygen depletion
sensor" is the pilot light.  It is designed so that the flame will
lift off the burner and go out as the oxygen is depleted.  You can
watch this effect if you put the heater in a large cardboard box and
seal it up, with a peep hole through the side.  I was curious about
how the "sensor" worked and did just that.

Another heater I have that also has a "sensor" also has a bimetal
strip on the pilot that lifts on over-temp, admits too much air and
again blows the pilot out.  I don't know if the Buddy has that or not,
as I haven't yet taken it apart to look.

From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: ever take apart a "Buddy Heater"?
Date: Sun, 03 Sep 2006 22:50:02 -0400
Message-ID: <1g4nf2194de0cif0hdmmsruonp0njk8ehs@4ax.com>

On Sun, 03 Sep 2006 05:44:44 -0600, boondocky@no.spam wrote:

>Neon John <no@never.com> wrote:

>>I have a Buddy but I don't like to use it in my RV.  With the open
>>flame it is possible to heat something that falls against it hot
>>enough to catch on fire.  I much prefer my Black Cat catalytic heater
>>when, for whatever reason, I don't want to use my furnace.  The
>>catalytic reaction is cool enough that even a piece of paper laid on
>>the surface of the thing barely browns a bit and will not get hot
>>enough to smoke.
>
>Hmmm.  The manual for the Olympian Wave-3 that I've been using in my
>worksop for the past few years says something about the pad being 600F
>which is plenty hot enough to burn wood.  Maybe the air at the
>protective screen has cooled down enough to be paper-safe, I don't
>recall ever having tried it.

Has nothing to do with air temperature.  It has everything to do with
radiant energy intensity and how fast the absorbed energy is
dissipated by the target object.  In any event, the max temperature
imparted to the target is 600 deg if the manual is correct (it
probably is).  Paper is a poor absorber of heat so I'd expect it to do
just fine in front of your heater just like it did mine.

>
>>To answer another question in this thread, the "oxygen depletion
>>sensor" is the pilot light.  It is designed so that the flame will
>>lift off the burner and go out as the oxygen is depleted.  You can
>>watch this effect if you put the heater in a large cardboard box and
>>seal it up, with a peep hole through the side.  I was curious about
>>how the "sensor" worked and did just that.
>
>So in effect the sensor is just a hole in the tubing?  I wonder if one
>would make it larger or smaller to defeat it.  To begin with, we're
>well above the 7000' altitude that they state as its operating limit.

No, it's simply a round tube, the diameter of which and the velocity
of the gas mix are chosen so that the flame just barely adheres to the
end of the tube.  When the oxygen concentration depletes, the gas
velocity is too high, the flame lifts from the end of the tube and
goes out.  The thermocouple cools and shuts the gas valve.

There are several ways to defeat the thing.  One way is to turn down
the pilot gas so that the velocity is low enough that the flame will
adhere at lower oxygen concentrations.  Most of the wall-mounted
(non-portable) heaters have a pilot adjustment in the combination
valve.

Another way is to put a coarse screen across the pilot opening.  This
provides multiple holes for the flames to adhere to.

Yet another is to replace the oxygen depletion pilot with a
conventional one.

Yet another is to move the thermocouple so that the main burner heats
it in addition to the pilot.  That way even if the pilot goes out the
thermocouple stays hot and the gas stays on.