How Can I extend my Generators Exhaust?

While using your Generator in an enclosed area, exhaust fumes can build up and cause air poisoning. The fumes are mainly carbon dioxide; which causes air poisoning and suffocation. Just as you’re getting used to the smoke, the noise from the running Generator engine becomes irritating and disruptive.

To prevent exhaust fumes from building up in your garage or workshop, you should extend your Generator’s exhaust. This article explains on how can I extend my Generators exhaust and options available for noise reduction.

Why Extend the Exhaust System?

how can I extend my Generators exhaustThe exhaust system redirects engine combustion fumes to the atmosphere. It also filters the impurities released for health and environmental reasons. However, standard exhaust pipes are merely ports no longer than 5 cm.

If your Generator runs in a closed space, the fumes will accumulate and make the place toxic for you. To avoid this, you can extend the exhaust system to an open area away from your home or working space. So learn on How Can I extend my Generator’s Exhaust?

Generic extension kits for portable Generators are available off-the-counter. However, heavier, stand-by Generators need custom-fitted extensions.

Measurements to be Taken

For an exact, air-tight extension fitting, the following measurements are required:

  1. Diameter of the Exhaust Port. You can get this by measuring manually using a Vernier caliper. Before making any measurements, ensure the Generator has been inactive for at least 24 hours. This will allow it to contract to its original diameter since metals expand when heated.
  2.  Using a tape measure, find the distance between the Generator shelter and location to the intended open area.

When purchasing the flex tube, give an allowance of 25% of the actual diameter. The pipe clamp, however, should be the actual diameter to prevent exhaust leaks. The length of the extension should be exact or longer.

2 Methods On How to Extend my Generators Exhaust

1. Using a Flexible Flex-tube

Materials required

  • Flex tube.

How Can I extend my Generator’s Exhaust?

  • Vernier Calipers.

How Can I extend my Generator’s Exhaust?

  • Pipe clamp.

How Can I extend my Generator’s Exhaust?

  • Tape Measure.
  • A Drill.

Before any fitting, your Generator should be inactive for at least 24 hours to allow for sufficient cooling. This will keep you safe from burns and the diameter will be constant.

Building the flex tube extension

  1. Clean the outer surface of the exhaust port. Remove any dust, paper, or plant material for smooth fitting.
  2. Slide the flex tube on top of the exhaust port until it’s fully covered.
  3. Fix the pipe clamp over the flex tube
  4. Tighten the pipe clamp. Tighten it enough to withstand vibrations from the Generator and wind.
  5. If your house has an outlet for the Generator drilled, lay down the flex tube to the outside using the shortest route. Avoid common pathways around the house or compound to reduce accident risks. This will reduce tripping on the flex tube and accidental burns since its metallic and the exhaust emits heat when the generator is running.

Otherwise, Drill an outlet in your wall. Ensure its level with the exhaust port in terms of height. This will prevent bending at the extension fitting point that will cause air leaks. Lay down the flex tube to the outside as far as possible from your home. Your pipe clamp should still be in place and tight.

  • Run the Generator. Check for leaks and any faults along the pipe to ensure its working.

2. Stainless-steel extension

Steel extensions are suitable for larger, permanently installed Generators. However, they’re not flexible as flex tubes.

Materials required

  • Threaded Galvanized stainless steel.
  • Floor flange.
  • Gasket maker or any airtight adhesive which can sustain high temperatures (287 o F – 800 o C).
  • A Drill.
  • A marker pen.
  • Hand-held metal saw.
  • Face-shield

These materials are on Amazon or can be purchased off the shelf. The steel pipe length should be of the correct length as it cannot be modified length-wise.

Building the extension

  1. Using a drill, unbolt the Cone-shaped spark arrestor housing the exhaust port.
  2. Place the spark arrestor on the floor flange and trace the outline using a marker pen. Shade the bolt openings for later drilling.
  3. Fasten the traced floor flange to a metal holder tightly to prevent it from jumping during cutting.
  4. Using a metal cutter, cut the floor flange following the outline you made earlier. Wear a face shield to prevent eye accidents.
  5. Fasten the cut floor flange and drill out the bolt ports. You can apply a drilling lubricant to prevent the drill from slipping due to friction. The end product should be a clone of the original spark arrestor.
  6. Tape the spark arrestor using painter’s tape. Apply the Gasket maker around the center and bolt openings. Ensure these openings are clear of any Gasket to avoid blocking the exhaust fumes.
  7. Mount the floor flange on top of the spark arrestor so that the gasket is in the middle.
  8. Bolt the spark arrestor to the Generator exhaust outlet with the flange mounted. Let the gasket cure for 24 hours.
  9. Unbolt the spark arrestor and unmount the floor flange. The gasket will have stuck on the cloned floor flange. Remove the painter’s tape from the spark arrestor trim out excess gasket from the flange.
  10. Insert the spark arrestor into the exhaust outlet and fit the cloned floor flange on top. Bolt the combination into the exhaust bolt ports. Depending on the excess width as a result of the Gasket, you may need new longer bolts.
  11. Insert the threaded steel pipe into the floor flange and rotate it gently until it’s tightly fitted. Your exhaust extension is now ready. Direct the pipe to an open area through an outlet in the wall of your home or Generator’s shelter.

If the available tubes cannot cover the distance between your home and the outlet open area, you can extend them using a flex tube. Slide a flex tube with a similar diameter on top of the steel tube. Tighten it with a clamp and apply the gasket maker at the joint to make it air-tight.

How To Muffle Noise In A Generator

The exhaust extension does not reduce the noise emitted by the Generator engine.

To muffle the sound, you can use one of the options below:

  1. Baffle Box.
  2. Sound deflectors.
  3. Acoustic Plywood board.
  4. Silencer Box
  5. Placing it on a rubber-padded ground.

These equipments are custom-made.

You can also check on how to reduce noise on your generator in this article


Let your portable Generator cool then unclamp the flex tube from the exhaust port. Storing the Generator with the extension fitted will damage the flex tube.

Since steel tubes are used with permanently installed Generators, the extension does not need disassembling.


Running a Generator in an enclosed environment poses a health risk. To redirect the fumes, you should fit an exhaust extension to your Generator. You can get a generic extension kit from Amazon or custom-build yours.

Custom-built extensions are better since they fit better compared to generic kits. In addition, the durability of the generic kits is lower.

Faqs On How to Extend Generator Exhaust System

How do I extend my portable Generator exhaust?

By fitting a flex tube to your Generator’s exhaust port.

How do I build a Generator exhaust extension?

You would require a flex tube and a clamp. Using a Vernier caliper, measure the diameter of your Generators’ exhaust port. Add an allowance of 25% and this is the diameter of a flex tube or steel pipe you should get.

To extend your exhaust, slide the flex tube/steel tube over your exhaust port and clamp it in place. Lay down the tube to the outside area.

How do I extend my RV Generator exhaust?

By fitting a flex tube or rigid steel pipe to the exhaust of the RV Generator.

Can I add a muffler to my Generator?

Yes. Generators support mufflers of various sizes for noise reduction

Can you use a silicone hose for the exhaust?

Yes. Silicon hoses are flexible and can handle temperatures of up to 287 degreesCelsius or 550 degrees Fahrenheit. This makes them suitable for exhaust systems generating heat of not more than 287 o C.

How hot does a Generator muffler get?

An average Generator muffler can be as hot as from 500 to 800 degrees Celsius or 1500 degrees Fahrenheit.

How do you vent a Generator box?

Build louvers to the walls and doors of the Generator box. Alternatively, you can drill or cut out vents in the walls of your Generator box.

How do I reduce Generator fumes?

An exhaust extension redirects fumes to an outside environment. This reduces Generator fumes in your workspace or home.

How Can I make my Generator quieter?

By fixing a Generator muffler, the Generator will be quieter by 10-15 decibels. Other methods are Baffle Box, Sound deflectors, Acoustic Plywood board, Silencer Box, Placing it on the rubber-padded ground.

What is an exhaust pipe?

Is a pipe redirecting exhaust fumes from the exhaust pipe to the outside environment? This prevents the Generator from overheating and breaking down.

Can you use PVC for the Generator exhaust?

No. PVCs (Polyvinylchloride) tubes handle the temperature of up to 140 degrees Fahrenheit. The average temperature of exhaust systems is 500 degrees Fahrenheit.

Can you add an exhaust extension to a Muffler?

No. Mufflers come with an exhaust extension. Adding a steel or flex tube to the Muffler exhaust will make your generator break down frequently. The backpressure between the muffler and the extension is different making your Generator faulty.

Do generators come with exhaust extension systems?

No. Generator manufacturers do not provide exhaust extension systems. However, they provide design specifications and measurements. You should refer to these specifications when building your exhaust extension system.

Check this Video On Extending Generator Exhaust System

About Steve Stuart

Steve Stuart is an electrical engineer who developed interest on generators during his school years. After school, he became a generator enthusiast. This is after encountering power supply problems at the area of residence where he lived. Power would be on and off and so food would go bad and the room heater would go off especially during winter. After trying the different generator brands for several years, Steve now provides information on the available brands and products in the market today. Based on his experience, he gives the do’s and the don’ts when it comes to generator use.

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