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Andrew vs. The Mosquito Magnet Part 1 -- An attempt to solve a problem with actual science

By Andrew Pollack on 05/10/2007 at 07:45 AM EDT

I live in Maine. Mosquitos also live in Maine. Many, many of them. Mosquitos also really like me. I must use up plenty of oxygen and exhale a great deal of carbon dioxide because that's what attracts mosquitos. Strangely, their bites don't irritate my skin much -- rather, the buzzing around my ears and eyes drives me insane.

The device to combat these tiny terrorists is the "Mosquito Magnet", The device uses a bare trickle of LP (Liquified Petroleum) gas from a 20 pound cylinder -- your basic grill propane tank -- to emit a small but constant amount of Carbon Dioxide into the air. It is roughly the equivalent of of a small animal breathing. A 20 pound cylinder lasts about a month. The device also uses a chemical scent to attract the little bugs most of the time (in some states, a kind of mosquito avoids that smell so they don't use it there). By operating all the time, day and night, the device really does attract a huge number of the little things from the area and captures them by simply using a fan to suck them in when they get close enough to the source of the CO2 and the attractant.

If used early enough in the season, they claim it can capture enough of them to interrupt the breeding cycle in your little area and give you a lovely mosquito free zone. And it actually works. When it works.

Here's the problem. This device is extremely sensitive to any contamination in the fuel by regular air. The smallest amount of regular air in the tank will cause the Mosquito Magnet to shut down with its flashing little red light indicating a problem. The manufacturer insists that you have your cylinders "purged" when you buy them (essentially filled and emptied in a way that LP gas displaces any regular air) and that you never ever use cylinder exchange services like Blue Rhino.

To me, this is utter bullshit. Services like this allow you to replace your empty cylinders by swapping them for a full one and paying for the fuel. This beats waiting for the fuel company or local U-Haul dealer or whatever to be open and having a qualified technician available to fill your own tank and charge you for the fuel you add. It's not much more expensive if you assume that your own tank is truly empty. Of course, it usually isn't. I suspect a good portion of the profit Blue Rhino makes comes from not having to fill them all from empty each time. That's fine with me, it's a good business model. Of course, it's very unlikely that Blue Rhino would purge every tank every time --that would waste thousands of dollars of fuel every day and would be very bad for the environment on top of being generally unnecessary. A little air in the tank doesn't cause your grill a problem, as the flame just burns it off.

Needless to say, my Mosquito Magnet has been temperamental and unreliable. Just when you think its working, you swap bottles and it stops again.

Last night I came up with what I hope is a simple, elegant, and brilliant fix. Through my hazmat training, I know that LP Gas has a specific gravity of 1.5 -- it's about half again as heavy as air. If it leaks, it will tend to pool at ground level making quite a dangerous situation. The LP fuel in one of these tanks is liquified by being under pressure. As you open the valve and release some of the gas, the pressure drops and some of the liquid fuel boils (literally) back into gas. There will always be a pool of liquified petroleum and a gas vapor area on top. I've actually seen this in seminars where they use a glass bottle to hold the LP so you can see the bubbles boiling off.

What I've decided to try is simple. Attach the LP cylinder that was too contaminated to use on the Mosquito Magnet, to the gas grill. Let it settle for a few hours. This should cause the heavier LP Gas to settle into a lower layer with the lighter regular air floating at the top of the tank. Slowly open the value and light the grill. Using the grill at it's lowest setting that will stay lit, cook something. A few minutes use should be enough. The air contamination won't bother the grill any -- the volume used is higher and air will just burn off. I suggest using the grill at it's lowest setting, as that will boil off the LP Gas more slowly and should produce less convection in the cylinder so that the air at the top doesn't mix back in so much.

If my theory holds true, I expect two things:

1. The partially used tank on my grill should power the Mosquito Magnet perfectly. So far, that has proved correct.
2. The contaminated tank, once used on the grill, should also provide excellent fuel for the Mosquito Magnet when the current tank runs dry.

We'll have to wait a few weeks for the results.

There are  - loading -  comments....

re: Andrew vs. The Mosquito Magnet Part 1 -- An attempt to solve a problem with actual scienceBy Nathan T. Freeman on 05/10/2007 at 08:43 AM EDT
I'm no physicist, but if there's contamination of air in the cylinder, and the
LP is heavier than air, and the valve is at the top, wouldn't the easiest
solution be to simply mount the cylinder upside-down, so that all the
uncontaminated LP is nearest the valve, and the air is trapped at the bottom
(now top) of the tank?

Or am I just demonstrating a profound ignorance of hardware hacking here?
Oh, no! That would be very very bad.By Andrew Pollack on 05/10/2007 at 09:28 AM EDT
Doing what you suggest would mean that the pool of LIQUID petroleum, not the
boiled off LP Gas would be at the opening of the valve. That would be very bad.
re: Andrew vs. The Mosquito Magnet Part 1 -- An attempt to solve a problem with actual scienceBy Carl Tyler on 05/10/2007 at 09:16 AM EDT
Sadly living in NH I also have mosquitos. Unfortunately I do react badly to
the bites, which makes that buzzing noise even more irritating when I hear it.

Mosquito magnet is definitly something I am looking into, although I still
think I am probably the bigger magnet.
Just be warned, these units are tempermental at best.By Andrew Pollack on 05/10/2007 at 04:22 PM EDT
I'm not sure I'd spend the money on this brand again.
re: Andrew vs. The Mosquito Magnet Part 1 -- An attempt to solve a problem with actual scienceBy Rick Wofford on 05/10/2007 at 09:57 AM EDT

Here is an exerpt from a Mosiquito Magnet Competitors web site(SkeeterVac by
Blue Rhino)
which basically says your idea is right on the money.

Why do I have to purge my tank?
Most tanks are purged before being filled. If you think there is air in the
tank, we recommend that you attach the LP tank to a grill and attempt to
light. Once gas flows and the grill lights, purging is complete.

How do I reset my tank?
With cylinder valve closed, disconnect tank from appliance. Let sit for about
15 minutes and the cylinder will automatically reset it self. Reconnect
cylinder to the appliance and slowly turn cylinder valve one to two turns.
re: Andrew vs. The Mosquito Magnet Part 1 -- An attempt to solve a problem with actual scienceBy francie on 05/10/2007 at 11:27 AM EDT
I live in the Caribbean (i.e. surrounded by water and warm temperatures all
year long) and we have a huge skeeter problem here.
With resources being a big scarce on the island, I successfully tried to the
'home grown' mosquito trap version detailed here:
although that was mostly out of curiosity.

I was actually looking at purchasing (and sh$pping - ugh) a mosquito magnet, so
this little tip/issue you desribe is quite helpful! Can you recommend a
particular type/kind?
Having just read that DIY version you posted, By Andrew Pollack on 05/10/2007 at 04:32 PM EDT
I would recommend you build four of them, put them at the corners of your yard,
and call it good.

This looks to be every bit as effective as the 300 dollar mosquito magnet and
much less problematic.

It's also silent, requires no power, and uses recycled materials.

I'm very impressed.
re: Having just read that DIY version you posted, By Charles Robinson on 01/04/2008 at 10:42 PM EST
The DIY thing doesn't work. I made several and put them in my yard. The only
thing they collected were leaves.
re: Andrew vs. The Mosquito Magnet Part 1 -- An attempt to solve a problem with actual scienceBy Roy on 05/22/2007 at 09:08 AM EDT
Andrew, I had the same idea last night (Hazmat Operations Level NFA grad 100
years ago) and removed the partially used tank from my grill and attached it to
my fickle machine. Thee green light stayed on longer than when I hooked it up
to my recently filled tanks, but after a while the magnet started calling for
propane again.

I called two service centers and they are angry with the new owners of Mosquito
Magnet because the repair places cannot get any parts from the new guys.

This thing works well on bugs when it works. I am having a hard time keeping
it working though and the company is adding to my problems.

I hope you have better luck than I.

well, here's a referenceBy Andrew Pollack on 05/22/2007 at 09:18 AM EDT
Copy this quick from the google cache, as the home page seems to be taken down.

He's got a list of parts, providers, and details about fixing these. They're
actually pretty simple.

I had mine apart the other day and the combustion chamber was full of soot.
mosquito magnet jmanley&hl=en&ct=clnk&cd=2&gl=us&client=firefox-a
re: Andrew vs. The Mosquito Magnet Part 1 -- An attempt to solve a problem with actual scienceBy Craig Wiseman on 06/05/2007 at 12:04 PM EDT
I think the Mosquitos have carried Mr. Pollack off.

Actually, I do hope you're just busy and that everyone is healthy, etc....
re: Andrew vs. The Mosquito Magnet Part 1 -- An attempt to solve a problem with actual scienceBy JP on 06/07/2007 at 11:02 AM EDT
Maybe this would work there.....

Solar Mosquito Guard
by Gaiam Real Goods

Weu2019ve received countless letters from satisfied Solar Mosquito Guard
owners, all with the same theme: u201CThese amazing things really work.u201D
Pocket-sized devices emit a barely audible, high-frequency wave that repels
some mosquito species. Includes keychain and belt clip. Battery fully recharges
in three hours of sunlight. Imported.
re: Andrew vs. The Mosquito Magnet Part 1 -- An attempt to solve a problem with actual scienceBy Jim on 06/19/2007 at 10:05 PM EDT
I have had the same problem all season, but i tried first with an almost empty
tank that was connected to the grill and it worked fine while I connected the
almost full tank which was not working to the grill as you suggested and voila
it worked also.
I had been using a bicycle pump to try to clear it but your solution worked
better and it has a scientific basis.

Thank you very much
re: Andrew vs. The Mosquito Magnet Part 1 -- An attempt to solve a problem with actual scienceBy bill hankins on 07/26/2008 at 01:28 PM EDT
i went thru everything suggested and it still wouldn't start. but when i put
12volts to the relay on the valve it didn't "click" it just chattered non stop.
i tapped it with a screw driver handle, reapplied current and heard a "click".
left the top off and hooked it back up and VOILA it ran. put it back together
and it is running as we speak.
re: Andrew vs. The Mosquito Magnet Part 1 -- An attempt to solve a problem with actual scienceBy Paul White on 09/16/2008 at 03:43 PM EDT
I have had a Mosquito Magnet working in my back yard for four years. This
summer I was afflicted with the "won't start" syndrome. I have tried the CO2
blowdown method repeatedly without success. I find it very hard to believe that
contaminant particles get stuck in the passage to the catalyst, blocking the
flow. My theory is that the catalyst gets poisoned after a while and won't
combine the air and propane any longer. After a period of about 5 minutes, the
Magnet apparently senses that the outlet temperature hasn't gone up and shuts
down. I don't know if there is any way to restore the (platinum?) catalyst.
re: Andrew vs. The Mosquito Magnet Part 1 -- An attempt to solve a problem with actual scienceBy Keith Mitchels on 09/23/2009 at 04:53 PM EDT
I had mine serviced by a company in CA, [ --------- ADVERTISEMENT REMOVED
----------- ]. Works better than when I first got it... they replaced some of
the parts with higher quality ones than the manufacturers use. Cost me less
than $200 and they cover it with their own warranty. They also sell new and
refurbished ones and they have really great prices on octenol and co2 ([
--------- ADVERTISEMENT REMOVED ----------- ]). Good luck!
re: Andrew vs. The Mosquito Magnet Part 1 -- An attempt to solve a problem with actual scienceBy Jay Bender on 11/16/2008 at 01:19 PM EST
If anyone is interested.... I sold and leased quite a few Mosquito Magnet
"PRO" models. The company decided NOT to sell me parts back then
and I ended up getting out of the business. The machine worked great
when operable, but had a couple of technical flaws. Since then, I have
obtained some hard to find parts for the "Pros" and can service this
discontinued model. Thanks, - Jay
re: Andrew vs. The Mosquito Magnet Part 1 -- An attempt to solve a problem with actual scienceBy Eric on 07/21/2012 at 08:54 AM EDT
Tried this and success. My Defender has had much trouble starting. After
cleaning the unit out completely, including combustion chamber, nozzle,
ignitor, thermocouple, etc it still would not start. After reading your
posting and trying it, because it made sense, my MM started right up after 2
tries. Would you say that this is an alternative method of 'purging' a tank
from an exchange system tank versus using a tank from an actual LP supply
re: Andrew vs. The Mosquito Magnet Part 1 -- An attempt to solve a problem with actual scienceBy Chris on 06/25/2014 at 03:18 PM EDT
Thank you very much, I too have concluded it has to be the propane tank, what a
brilliant solution.
re: Andrew vs. The Mosquito Magnet Part 1 -- An attempt to solve a problem with actual scienceBy Leong (Kuala Lumpur) on 01/18/2015 at 12:28 AM EST
Hi Andrew and all,
This product is not sold in Malaysia and obviously no service dealers anywhere
within 1000km.

I happen to chance upon a unit back in 2011 (brought in by a hardware retail,
and they have in stock for only 2-3 units). They've displayed it for the
longest time (maybe 1-2 years), and decided to put it back into the store room
after collecting inches of dust, and nobody cared/dared to try despite the
reports of rampant Dengue fever caused by rampant tiger/aedes mosquitoes here.

Yours truly, despite all odds, forked out the money, took the "no warranty
risk", and bought the unit at a probably import price (they reduced it 50%
price with no warranty, and "don't call us" warning).

Thank God for internet, and I was able to learn / watch videos on how to get
this unit up (of course, prior to buying, I watched tonnes of it too).

Sadly, I suffered the same fate - bloody thing wouldn't start properly. And
I've been trying all sorts of tricks found on the internet, but mostly, it was
about "neutralising" the "won't start" with quick clears.

Just today, I found this link.
I have just yanked my kitchen LPG tank (half use) into the defender's tank
position, quick cleared it properly, and for the first time after buying the
product for more than 6 months, the fan (sound) has been running for more than
30 mins! Good God...I wish I found this link earlier!

And I hope this IS the solution!

Many Thanks to Andrew, and many thanks to all the contributors here who in one
way or another, shared your experience and gave me enough ooomph to try this
"one last time" before I send it to the junk yard.

Honestly, with the science today, air impurity in propane can cause such a
machine to stall? Unbelieveable, but believe it.

Thanks guys.
All the way from hot humid mosquito friendly Kuala Lumpur Malaysia.
re: Andrew vs. The Mosquito Magnet Part 1 -- An attempt to solve a problem with actual scienceBy Leong (Kuala Lumpur) on 01/18/2015 at 05:00 AM EST
Well guys, 3 hours into the email I just sent, I suffered the same "defender
won't start".

What I did
Took out my 2 weeks old 14lb kitchen LP tank, and switched it with the "brand
new one". The logic is after 2 weeks, the kitchen LP tank would have been

It worked for 30 mins (at least I was monitoring that long), and 3 hours later,
when I checked, it had stopped whirring (the fan), and the only thing I can see
is the red blinking lights again.

I had done a quick valve clear (full 15 mins until hissing all stopped), and it
still doesnt work.

I really do not know what to do now. Please advice, anyone?

re: Andrew vs. The Mosquito Magnet Part 1 -- An attempt to solve a problem with actual scienceBy DH Wisconsin on 05/27/2015 at 06:51 PM EDT
5/2015- This absolutely works!! I had tried everything on a newly refurbished
Liberty. Thank you for your amazing theory!!

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