Generator exhaust

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  • 10-32

    Sharpshooter
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    Nov 28, 2011
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    I've been thinking about installing some type of exhaust setup in my garage so I can run my generator from inside my garage so I can reduce the noise my neighbors hear and so I don't have to worry as much about it being stolen.

    I was thinking of something similar to a dryer exhaust but with a in-line fan and a co2 alarm ground level about half way between the generator and the exhaust port in the wall.

    Has anyone else done anything like this or use another type of exhaust system with their generator? Any input and opinions about the system are welcome. Thanks
     

    DangerousDave

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    Jan 3, 2014
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    I've seen a couple of set-ups where they used metal flex pipe to run their exhaust outside. If you used a dryer duct, it would have to be metal as plastic would melt from the heat of the exhaust.
     

    10-32

    Sharpshooter
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    Yes, I wanted to keep everything metal if possible. I'm even looking at buying a in-line fan with metal blades over the plastic blades. It's only a few dollars more.
     

    Butch627

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    For decades auto mechanics ran car exhausts through a hole in the garage door so they could run the engine inside. They had round holes cut in the door with special covers that would close when not in use. I am sure you can still get those covers. As for the pipe Napa should have flex pipe you can use
     

    4651feeder

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    KIS, the Amish around me use small diameter flex exhaust pipe to run washing machine gas engine exhaust outside. Unless you're moving the generator, threaded 1" black iron pipe could be a solution.
     

    BigBoxaJunk

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    There are some good Youtube videos showing different set-ups for that. I've been thinking of doing the same thing, maybe even adding a car muffler to make it quieter. One thing you need to do is to make sure that you have a fresh air vent into your garage, preferably on a wall opposite of where the exhaust is situated, so that the generator intake doesn't draw exhaust gases back into the garage.

    I've also bought the stuff to plumb my gas generator up for propane as well. I'm using a new regulator and hose, made for a gas grill, and the needle valve from a propane weed-burner torch that I already had.
     

    JettaKnight

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    I've seen a couple of set-ups where they used metal flex pipe to run their exhaust outside. If you used a dryer duct, it would have to be metal as plastic would melt from the heat of the exhaust.
    All dryer duct is metal - plastic hose is verboten for the same reason. That crap is for bath fan exhaust only.
    I've been thinking about installing some type of exhaust setup in my garage so I can run my generator from inside my garage so I can reduce the noise my neighbors hear and so I don't have to worry as much about it being stolen.

    I was thinking of something similar to a dryer exhaust but with a in-line fan and a co2 alarm ground level about half way between the generator and the exhaust port in the wall.

    Has anyone else done anything like this or use another type of exhaust system with their generator? Any input and opinions about the system are welcome. Thanks
    You want a carbon monoxide alarm, not a carbon dioxide alarm.
     

    ClydeB

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    Sep 17, 2012
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    I will admit to a bit of redneck engineering. I was using my Ford Explorer as a generator during a power outage (back in 08). Parked it in the garage. Took the hose off my shop vac. Put it on the exhaust pipe and out the bottom of the garage door. Not the safest thing. But I lived. And the shop vac hose survived too. Nowadays I put the generator back out on the rear deck above the walkout basement. There's no ground level access to the deck. Ventilation takes care of itself.

    One thing I did think about back then was doing was something like a sewer pipe exhaust setup to the top of the garage roof. Let the residual exhaust heat work for you by creating a draw in the pipe.
     

    JeepHammer

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    If you want the engine to run correctly & efficiently, don't forget an 'Expansion' chamber.
    This is as easy as a car muffler, just someplace for heated gas to expand fairly close to the engine.

    This is fairly self explanatory, I would recommend exhaust pipe (and muffler) from the parts store or exhaust shop.
    It's cheap, many parts stores have short pieces and clamps, any exhaust shop can bend tubing into custom shapes, etc.
    A short (I emphasize short) run of OVERSIZED flex pipe to attach the generator to your muffler/exhaust system.
    Common vehicle exhaust pipe will be oversized (allowing for both low restriction flow & expansion) for your generator.

    *IF* you intend to run the generator for a long while, I would also suggest increasing the size of the air filter.
    Small sponge foam air cleaners are REALLY restrictive in the intake tract, while a smaller common car paper element filter is easily replaceable, not nearly as restrictive, inexpensive and does a better job for this application.
    Mowers & chain saws are in high dust/grit enviormental situations, while a genset in the garage isn't going to need the excessive (restrictive) filtering the mower or saw will need.

    What I do for myself & customers,
    A common, less restrictive air filter with a lot more surface area that works longer before needing cleaned or replaced.
    A supply of replacement air filters.
    A supply of crankcase oil, for small generators, that's usually a METAL 5 gallon can clearly marked as engine oil.
    A supply of oil filters if the engine uses a filter.
    A stand that gets the genset up off the floor, both for longevity of the genset and to make oil changes easier.
    I replace drain plugs with metal ball valves, this makes for no tools oil changes.
    I also make sure there is a supply of ignition parts, spark plugs, an extra magneto (metal 'E' shaped frame with plastic moulded around it and a spark plug wire coming out of it), and if the genset is larger, breaker points or ignition module & tools/instructions on how to replace the ignition components.

    In a full on generator setup, I also setup dual fuel capabilities.
    Any diesel or gasoline generator will run on propane (LPG) or natural gas, and it's dirt simple to switch over.
    Gasoline engines will run along fine on alcohol, but that takes MUCH more work to switch over.

    Keep in mind here, LPG (Propane) will store INDEFINITELY, while gasoline, alcohol & diesel do have a shelf life...
    If you live somewhere that has city gas service (CNG, 'Natural' gas) this service will be working when the power is out long term.
    No rotation of fuel, no treating fuel, no headaches from fuel degrading gaskets or turning into sludge while the genset waits to be used.
    There are definitely advantages to LPG/CNG over liquid fuels.
     

    churchmouse

    I still care....Really
    Emeritus
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    Dec 7, 2011
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    We put the gennys in the shop. I have made adapter flanges to secure the pipe to the engines. I have 2 stock mufflers from the spouses Harley that were in the shed. They are perfect for this. Flex pipe under the door and mufflers are outside. Whisper quite.
    They take a minute to set up but for ease of mind well worth it.
     

    BigBoxaJunk

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    Feb 9, 2013
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    Does anyone worry about a generator catching fire inside a building?

    My dad was running one outside years ago, and I don't know how it happened, but his caught fire and the generator part burned up. I don't know if generators have an inherent danger of catching on fire, or if it was something stupid that my dad did (memory of my dad indicates that both are possible).
     

    Alamo

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    Oct 4, 2010
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    Texas
    If you want the engine to run correctly & efficiently, don't forget an 'Expansion' chamber.
    This is as easy as a car muffler, just someplace for heated gas to expand fairly close to the engine.

    This is fairly self explanatory, I would recommend exhaust pipe (and muffler) from the parts store or exhaust shop.
    It's cheap, many parts stores have short pieces and clamps, any exhaust shop can bend tubing into custom shapes, etc.
    A short (I emphasize short) run of OVERSIZED flex pipe to attach the generator to your muffler/exhaust system.
    Common vehicle exhaust pipe will be oversized (allowing for both low restriction flow & expansion) for your generator.

    *IF* you intend to run the generator for a long while, I would also suggest increasing the size of the air filter.
    Small sponge foam air cleaners are REALLY restrictive in the intake tract, while a smaller common car paper element filter is easily replaceable, not nearly as restrictive, inexpensive and does a better job for this application.
    Mowers & chain saws are in high dust/grit enviormental situations, while a genset in the garage isn't going to need the excessive (restrictive) filtering the mower or saw will need.

    What I do for myself & customers,
    A common, less restrictive air filter with a lot more surface area that works longer before needing cleaned or replaced.
    A supply of replacement air filters.
    A supply of crankcase oil, for small generators, that's usually a METAL 5 gallon can clearly marked as engine oil.
    A supply of oil filters if the engine uses a filter.
    A stand that gets the genset up off the floor, both for longevity of the genset and to make oil changes easier.
    I replace drain plugs with metal ball valves, this makes for no tools oil changes.
    I also make sure there is a supply of ignition parts, spark plugs, an extra magneto (metal 'E' shaped frame with plastic moulded around it and a spark plug wire coming out of it), and if the genset is larger, breaker points or ignition module & tools/instructions on how to replace the ignition components.

    In a full on generator setup, I also setup dual fuel capabilities.
    Any diesel or gasoline generator will run on propane (LPG) or natural gas, and it's dirt simple to switch over.
    Gasoline engines will run along fine on alcohol, but that takes MUCH more work to switch over.

    Keep in mind here, LPG (Propane) will store INDEFINITELY, while gasoline, alcohol & diesel do have a shelf life...
    If you live somewhere that has city gas service (CNG, 'Natural' gas) this service will be working when the power is out long term.
    No rotation of fuel, no treating fuel, no headaches from fuel degrading gaskets or turning into sludge while the genset waits to be used.
    There are definitely advantages to LPG/CNG over liquid fuels.


    Interesting. thanks for posting.
     

    WhitleyStu

    Keep'em Scary Sharp!!!
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    11   0   0
    Feb 11, 2009
    1,466
    63
    Whitley County/Allen County
    18 years ago I purchased a 25' roll of flex exhaust from NAPA that was just large enough to fit over the exhaust pipe on the generator's engine. A single muffler clamp keeps the flex exhaust on the engine. The 25 HP Kohler Command has 180+ hours on it and running great. If it's nice I run the generator outside, but in rain or snow we run the generator just inside the garage close to the garage door so the flex pipe is only approximately 8' long.
     

    Butch627

    Master
    Rating - 100%
    24   0   0
    Jan 3, 2012
    1,698
    83
    NWI
    If you want the engine to run correctly & efficiently, don't forget an 'Expansion' chamber.
    This is as easy as a car muffler, just someplace for heated gas to expand fairly close to the engine.

    This is fairly self explanatory, I would recommend exhaust pipe (and muffler) from the parts store or exhaust shop.
    It's cheap, many parts stores have short pieces and clamps, any exhaust shop can bend tubing into custom shapes, etc.
    A short (I emphasize short) run of OVERSIZED flex pipe to attach the generator to your muffler/exhaust system.
    Common vehicle exhaust pipe will be oversized (allowing for both low restriction flow & expansion) for your generator.

    *IF* you intend to run the generator for a long while, I would also suggest increasing the size of the air filter.
    Small sponge foam air cleaners are REALLY restrictive in the intake tract, while a smaller common car paper element filter is easily replaceable, not nearly as restrictive, inexpensive and does a better job for this application.
    Mowers & chain saws are in high dust/grit enviormental situations, while a genset in the garage isn't going to need the excessive (restrictive) filtering the mower or saw will need.

    What I do for myself & customers,
    A common, less restrictive air filter with a lot more surface area that works longer before needing cleaned or replaced.
    A supply of replacement air filters.
    A supply of crankcase oil, for small generators, that's usually a METAL 5 gallon can clearly marked as engine oil.
    A supply of oil filters if the engine uses a filter.
    A stand that gets the genset up off the floor, both for longevity of the genset and to make oil changes easier.
    I replace drain plugs with metal ball valves, this makes for no tools oil changes.
    I also make sure there is a supply of ignition parts, spark plugs, an extra magneto (metal 'E' shaped frame with plastic moulded around it and a spark plug wire coming out of it), and if the genset is larger, breaker points or ignition module & tools/instructions on how to replace the ignition components.

    In a full on generator setup, I also setup dual fuel capabilities.
    Any diesel or gasoline generator will run on propane (LPG) or natural gas, and it's dirt simple to switch over.
    Gasoline engines will run along fine on alcohol, but that takes MUCH more work to switch over.

    Keep in mind here, LPG (Propane) will store INDEFINITELY, while gasoline, alcohol & diesel do have a shelf life...
    If you live somewhere that has city gas service (CNG, 'Natural' gas) this service will be working when the power is out long term.
    No rotation of fuel, no treating fuel, no headaches from fuel degrading gaskets or turning into sludge while the genset waits to be used.
    There are definitely advantages to LPG/CNG over liquid fuels.

    I have never heard of this expansion chamber concept outside of a 2 stroke. Assuming that one has the factory muffler on the engine I don't understand why an expansion chamber is needed. To my knowledge even something like a School bus with its 20ft exhaust pipe doesn't have anything but a cat and muffler on it. Can you please give some links to the science behind this reasoning?

    If the compression and timing are not optimized to run on Natural gas or propane your generator will not make its rated power, One should make sure you will have enough watts to run what you need or reduce your loads if using those fuels.

    When talking about points and magnetos I was under the impression that they have not been used on new equipment for decades, are your customers using 30 year or older generators for emergency use?

    You mentioned your customers, what kind of business are you running?
     

    JeepHammer

    SHOOTER
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    Aug 2, 2018
    1,904
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    SW Indiana
    I made pretty good money when the whole '2012 End Of The Earth' thing was happening, people with serious money got caught up in that.
    Now it's mostly off grid or grid intertie/homesteads for 'Hipsters' that make money.
    'Back To The Earth' (as long as I have Starbucks, Netflix & high speed internet so I can post selfies) generation aren't exactly bursting with common sense...

    I have to talk S-L-O-W to hipsters, they don't seem to connect HOT STUFF with burning the house down...
    But they can qualify for every credit card on the planet!

    Personally, I like the arrangement that Cat & other big gensets have, fuel tank on bottom, leak proof built in fuel pump/hard lines, enclosure to keep unauthorized people (read: Idiots) from fingering everything, and actual exhaust pipe for exhaust.
    Fuel tank on bottom means a fuel pump, something else to go wrong, but it keeps fuel off a hot engine.
    More ways that just filling the tank and slopping fuel, a fuel tank on top has a gas fitting, valve, line & usually filter that can all fail dumping fuel on a hot engine. With small generators, that's all plastic & rubber, which WILL eventually fail.
    It's been 30 years since I've seen a metal fuel tank on any small engine powered device...

    Anytime I see a beard & man bun the price automatically goes up about 50%, it's just so difficult to get them to answer the most simple questions, and they won't make a decision on anything... (But have an opinion on everything)
     

    JeepHammer

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    Aug 2, 2018
    1,904
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    SW Indiana
    I have never heard of this expansion chamber concept outside of a 2 stroke. Assuming that one has the factory muffler on the engine I don't understand why an expansion chamber is needed. To my knowledge even something like a School bus with its 20ft exhaust pipe doesn't have anything but a cat and muffler on it. Can you please give some links to the science behind this reasoning?

    Probably not, it's something you wouldn't know about unless you flow tested engines.

    It's pretty easy to see in most small gasoline engines, a muffler that's way oversized for the exhaust port size to reduce back pressure and stop reversion (reversal of exhaust gas flow) when cold intake charge hits the cylinder while the exhaust valve is still open.
    Intake & exhaust valves are open at the same time, exhaust is closing when intake starts opening, it's called 'Overlap' when discussing camshafts, camshafts being what opens/closes the valves.

    In larger gasoline engines, and particularly when factory or aftermarket headers are used, the tube is specifically sized for diameter & length to keeps exhaust gasses flowing easily IN ONE DIRECTION.
    Collectors, or mufflers are used as expansion chambers to limit reversion, and to keep the scavenging effect from removing incoming fuel & air mixture from the cylinder and out the exhaust port.

    Anti-reversion headers caught on so fast in the late 70s/early 80s almost no one noticed, and since the technology couldn't be patented, every maker started producing AR headers, none too bright consumers didn't even notice, but power outputs did!

    A larger capacity chamber, like a header collector or muffler, stops any significant reversion from the cooling chamber drawing exhaust gasses (non combustable gas) that limits proper combustion in the chamber,
    Along with runner tube length/side scavenging incoming fuel/air from the cylinder is also limited, unless you have a stupid long overlap in camshaft timing.

    Since the OP also specifically listed 'Quiet' as an objective, allowing the hot, and potentially fuel ladened gasses to expand at a controlled rate without extra oxygen, there isn't the exhaust noise small engines usually make.
    Since he wanted both exhaust temp safe, and quiet, I suggested a car muffler which fits the bill on both counts, and is VERY cost effective to boot.

    If the compression and timing are not optimized to run on Natural gas or propane your generator will not make its rated power, One should make sure you will have enough watts to run what you need or reduce your loads if using those fuels.

    While the energy of the fuel is slightly less, virtually all the small engine generators I've seen made in the past 30 or more years have a (mechanical) speed governor.
    This means the engine is quite capable of producing MORE RPM/Power than the generator needs, and the governor is used to LIMIT RPM, and that particular speed is the correct RPM to produce properly phased (60 Cycles or Hertz in the U.S.) power from the generator.

    Ignition timing doesn't change in small engines, there is no vacuum advance or centrifugal advance, although some can have 'Weather Vane' type arrangement to slightly change timing to keep the engine from dying when loaded excessively.
    These are rare as hens teeth on small gensets since they are mechanically governed to run a specific RPM.

    When talking about points and magnetos I was under the impression that they have not been used on new equipment for decades, are your customers using 30 year or older generators for emergency use?

    Virtually all single cylinder lawn mower style engines use a magneto to produce spark energy.
    No battery, no breaker points since there is no ignition coil.
    The magneto is the 'E' shaped metal frame with a spark plug wire coming directly out of it.

    514ebxbED4L._SL1000_.jpg

    A pair of magnets in the flywheel pass the magneto (coils of wire in a 'Plastic' housing on the metal 'E' shaped frame, magnets passing a coil of wire INDUCE an electrical current, which is passed to the spark plug wire/spark plug.
    No breaker points, no transformer ignition coil, the engine is interested deed to run a single speed and more or less a single load, so no vacuum or centrifugal advance.

    To explain how the above works (electromagnetic induction) would take a week with examples and hands on training, so I'm not going to attempt it...
    Suffice to say, the electromagnetic link between magnetic fields and electrical conductors is how every electron you use is produced,
    In generators, in alternators, in starters and every electric motor.
    All it takes to produce a coherent, useable electric potential is a magnet & a coil of wire (conductor).

    Once that current is made, the electromagnetic link is used to step up the voltage, or to step down the voltage.
    We call those devices 'Transformers', as in the ignition transformer coil that transforms 12 Volts into 35,000 volts to fire the average car sparkplug reliably.
    Magnetos & transformer coils are NOT the same thing.

    In the case of a magneto ignition, the flywheel moved the magnets, the field passes through the coil of wire on the metal frame, and it's enough to fire the spark plug directly...

    You mentioned your customers, what kind of business are you running?

    I own a machine shop & manufacturing business.

    ------------

    And for your information....

    Since magnetos are capable of MUCH LONGER duration of spark energy than simple breaker points/transformer coil ignitions, magnetos are still used on exotic fuel high performance vehicles, like top fuel racers burning alcohol (with or without nitro).
    Spark energy has three components, Voltage, Amperage & Duration.
    Magnetos are excellent at producing all three components of the spark energy, particular amperage & duration, which makes them excellent for exotic and/or hard to ignite fuels.

    Voltage, the 'Pressure' in the system. The higher the voltage, the wider gap the voltage can ionize, the first step to a spark in the sparkplug gap.
    Amperage is VOLUME, Amperage determines how hot the spark is going to be.
    Duration, the time the spark stays in the gap. The longer & hotter the better chance of getting a proper ignition started in the fuel charge.
    While consumer companies rant and rave about how high the volts are with their product, the truth is about 35,000 volts will fire ANY engine.

    Transformer ignition coils trade amperage (@ 12 Volts) for voltage, transforming amps into volts.
    Amps is what actually lights the fire, the higher the amperage, the hotter the spark in the gap, and the better chance you will get the cylinder lit properly.

    Duration depends entirely on how many amps were converted to volts, super high volts robs amperage making for a weak, short duration spark...
    You can adjust the duration (and amperage delivered) by closing up the spark gap a little, but then you run into the problems with surface area of the spark in the gap, too little surface area and the cylinder doesn't fire correctly...

    It's a balancing act that most average consumers, and parts changer mechanics never know about, this is engineering stuff, which I did for a few years...

    -------

    For the 'SHTF' guy, a magneto doesn't need a charging system or battery to run. Simply pull or push start the engine and it will run until you shut it down.
    A magneto is impervious to outside electromagnetic interference, so perfect for the guys worried about an EMP...
    *IF* an EMP hit a magneto, it *Might* fire the spark plug it was connected to, but since there are no moving parts, and no semi-conductors, no amount of EMP would effect a magneto ignition system.
     
    Last edited:

    red_zr24x4

    UA#190
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    Mar 14, 2009
    28,797
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    Walkerton
    KIS, the Amish around me use small diameter flex exhaust pipe to run washing machine gas engine exhaust outside. Unless you're moving the generator, threaded 1" black iron pipe could be a solution.

    I have a generator in my work truck, which is an enclosed utility box. I run my exhaust through 1" BIP and leave the one back door open for the exhaust. No issues doing this
     

    10-32

    Sharpshooter
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    Nov 28, 2011
    631
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    B-Burg
    Thanks for the input everyone.

    JeepHammer, thanks for putting the time you did into those post. They kinda left scratching my head wondering how much more money am I going to have to put into this.

    I think what I'm going to end up doing is attaching a generic muffler from Advanced to the factory "muffler" because the the genny is loud as hell. Then I'm going to use dryer exhaust pipe and run it to one of those metal ports the automatically close when not in use. I decided to use dryer exhaust pipe from Lowe's because it's almost half the cost of the stuff at NAPA.
     

    actaeon277

    Grandmaster
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    Nov 20, 2011
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    Merrillville
    Whatever you do, please..
    1) do it well. Don't half-ass it.
    2) carbon monoxide detectors. At least one. 2 would be better. If one fails, the other could pick up. Also, CO gas travels in "pockets".

    CO detectors are not real cheap.
    But they're cheaper than your life.
     

    10-32

    Sharpshooter
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    1   0   0
    Nov 28, 2011
    631
    18
    B-Burg
    Whatever you do, please..
    1) do it well. Don't half-ass it.
    2) carbon monoxide detectors. At least one. 2 would be better. If one fails, the other could pick up. Also, CO gas travels in "pockets".

    CO detectors are not real cheap.
    But they're cheaper than your life.

    I already have one in the garage, just going to relocate it, I also have one in the utility room where you come in from the garage because of the furnace and water heater. CO is one of the reasons I was thinking of using a in-line fan for the exhaust. After thinking about it, suction on the exhaust just didn't seem like a good idea. I may install a 2nd exhaust port with a fan so I could vent the garage if needed. A test run while monitoring the CO levels will make that decision.
     
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