How to Vent a Generator in a Garage: Ultimate Guide

Running a generator in the garage is one thing no one will advise you to do, including me. That’s because of the health risks associated with the emission of carbon monoxide by a generator. However, there are instances where we don’t really have a choice but to run it in the garage.

With the right knowledge and some creativity, you can safely run your generator in the garage with zero health risks or issues. And that is what you will learn in this post — how to vent a generator, so you can safely run it in a garage.

There are two ways to vent a generator in a garage. The first option is to connect the generator’s exhaust to a long flexible exhaust tube and route it to a well-ventilated area. The second option is to connect the generator’s exhaust to a PVC vent pipe outside that discharges the fumes into the atmosphere.

I will walk you through a step by step guide on how to vent your generator, both ways. We’ll also take a look at both options and which one you should go for based on your situation and budget. Now, let’s discuss why it’s crucial to vent a generator placed in a garage. 

Why is it important to vent a generator in a garage?

It’s no news that generators emit high levels of carbon monoxide. This is a known gas which is very dangerous to our health and safety. In fact, there have been several incidents and reports in the past that confirms how hazardous this gas is. Many homeowners have been hospitalized, while some have lost their lives because of high exposure to carbon monoxide. 

Thus, it is not recommended to run a generator in an enclosed space, which includes the garage. It is always advised that you run your generator outside, at least 20 feet away. We discussed that in detail in this article. I recommend you check it out.

However, the problem is the only time we may need to run our generator is when there is a power outage. And these outages are usually caused by big storms and harsh weather conditions. These are not ideal weather conditions to run a generator outside. You risk damaging your generator, or potentially electrocuting yourself. This is why many homeowners are left with no option than to run it in the garage.

Running your generator inside the garage the wrong way will put you and your family at high risk. That’s because the generator’s fumes will eventually seep into your home, and bad things can happen, which is why you need to vent your generator. 

In this case, venting your generator means routing the harmful carbon monoxide directly from the generator to a well-ventilated area. This will keep your garage and home safe from this poisonous gas.

In essence, to safely run a generator in the garage, you need to route the harmful carbon monoxide away from your home. And you will learn how to do that in this article. Now let’s get into it.

The Two Ways to Vent a Generator in a Garage

As I mentioned earlier, there are two ways to vent a generator in a garage

Option 1: Connect the generator’s exhaust to a long flexible tube

Option 2: Connect the exhaust to a fixed PVC vent pipe outside

I consider Option 1 as a temporal approach. It is also the simplest. But it works just as good as option 2. Go for option 1 if you don’t have permission to make any structural changes to your house. If you live in a rented house, I recommend you go with option 1 to avoid future issues with your landlord.

Option 2 is a more permanent option, but a bit too technical. If you are DIY-savvy and have the right tools, I recommend you go with option 2. Also, if you have permission to make structural changes to your house, I recommend this option. That’s because after venting your generator with this approach, you can walk into your garage anytime and start your generator. And you won’t have to worry about any ventilation problems.

Option 1: Connecting the generator’s exhaust to a long flexible tube

Let me walk you through the step by step process on how to vent your generator using this Option 1.

1. Measure the diameter of the generator’s exhaust

You want to know how wide the exhaust is. It will be important in the next step. Using a tape measure, measure the diameter of the generator’s exhaust.

2. Find the right flexible exhaust tube size.

The next step is to go shopping for a flexible exhaust tube extension. Flex tubes are recommended because they are easy to move about and route through different spaces. The goal is to find a tube that is slightly bigger than the generator’s exhaust. That’s because you will slide it over the exhaust and then clamp it. This will prevent any fumes from leaking.

As a rule of thumb, find an exhaust tube that is 1/4 inch bigger than the generator’s exhaust. For instance, if the exhaust’s diameter is 1″, a flexible tube with a diameter of 1 ¼” will be an excellent fit. 

Now let’s talk about the required length. You want a flexible exhaust tube which is long enough to reach a well-ventilated area. I recommend a flexible, which is at least 20′. However, if 20 feet away from your garage is not a good place to discharge carbon monoxide, then you may need to get a slightly longer tube.

FORTLUFT Galvanized Exhaust Flex Tube (on Amazon) is an excellent example of what you need for this project. The entire surface is galvanized, meaning it won’t easily rust. This is an essential feature because chances are you will be using this tube in the rain. 

Also, they make these tubes in seven different sizes so you will find a size that works well with your generator’s exhaust.

3. Find the right clamp for your generator’s exhaust.

You also need to pick up a clamp. This will be used to tightly seal any gap between the generator’s exhaust and the flex tube. And that will prevent any carbon monoxide leakages in the garage.

Ideally, you should find a clamp that has the same diameter as your generator’s exhaust. That will provide the best clamp possible.

AMAAM’s Heavy Duty U-Bolt Clamp (also on Amazon) will get the job done. Unlike the other brands, AMAAM’s clamps are made of hard steel, making it very tough. Also, they are have been coated to prevent rusting.

The reason why I’m recommending this particular clamp is, they have fourteen different sizes to choose from. This means you will definitely find a clamp with the same diameter as your generator’s exhaust, or something close it. 

4. Attach and secure the flexible exhaust tube to the generator’s exhaust

I think this part is pretty self-explanatory. Slide the generator’s exhaust into the flex tube. Once you are done, secure it with the clamp.

Make sure that the clamp is tightened very well to ensure there are no leaks.

5. Route the flexible exhaust tube to a well-ventilated area

At this stage, you are pretty much done with the project. Any time you want to run your generator, route the other end of the flex tube outside your garage to a well-ventilated space. You can route it through the windows, or under a slightly opened garage door. Whatever works for you.

When you stop the generator, you wait for some minutes for the residual fumes inside the flex tube to come out, and then you roll it up and store it back in the garage.

You can decide to detach the tube from the exhaust after every use. However, if you don’t move your generator around too often, I don’t see the need. 

Now let’s move on to Option 2

Option 2: Connecting the generator’s exhaust to a PVC Vent Pipe

As I mentioned earlier, Option 2 involves a little bit of work compared to option 1. but if you are handy with tools, this will be an easy project. 

Essentially, we will use PVC pipes to make an air vent that is attached to the side of our garage. It will extend high above the roof peak so that fumes will be discharged into the atmosphere without getting into our homes.

We will then connect our generator’s exhaust to the air vent we created with a flexible exhaust extension tube.

Now let’s get into it.

1. Measure the diameter of your generator’s exhaust

I have already explained this in the first option. It’s the same procedure here as well. Measure your generator’s exhaust diameter with a tape measure, and record the value. This is very important because I’m going to refer to it a lot in this guide.

2. Find the right flexible exhaust tube size.

Once again, you will need a flexible exhaust tube. Find an exhaust tube that is slightly bigger than the generator’s exhaust. A ¼” wider than the generator’s exhaust will get the job done. 

We don’t need a very long flex tube for this option. We are only using it to connect the generator’s exhaust to a PVC vent pipe we will later install. 

The length of the flexible tube will depend on where the generator is placed in the garage. If the generator is positioned close to the garage wall where the PVC vent pipe will be attached, a 3′ flex tube will be sufficient. 

Once again, I recommend FORTLUFT Galvanized Exhaust Flex Tube (on Amazon). That is because you have different flex tube sizes and lengths to choose from. 

3. Find the right clamp for your generator’s exhaust.

As I explained in the first option, find a clamp with the same diameter as your generator’s exhaust. For this method, you need two clamps, however. So purchase two clamps of the same size. 

You will definitely find an option from AMAAM’s Heavy Duty U-Bolt Clamp collection (Amazon) that perfectly fits your generator’s exhaust. 

4. Attach and secure the flexible tube to the exhaust

Slide the generator’s exhaust into the flex tube, and then secure it in place with the clamp. Tighten the clamp with a spanner, and ensure there are no leaks. This is important because you don’t want any carbon monoxide traces in your garage.

5. Drill a hole inside the garage wall and run the flex tube through it

Now, at this point, you need to find a perfect place on the side of your garage where you can attach a PVC pipe vertically.

Once you find that perfect spot, drill a hole inside the hall close to the spot. The hole should be at least 1′ off the ground.

Here are the tools you will need to drill the hole

  1. Drilling machine
  2. ⅛” drill bit
  3. 2 ½” hole saw

To drill a hole in your garage wall,

  1. First, mark the spot with a pencil. The spot should be at least 1 feet off the ground.
  2. Drill a pilot hole in the wall using the ⅛” drill bit
  3. Set the hole saw center bit to protrude ⅜.”
  4. Now drill slowly with steady pressure with the 2 ½” hole saw.
  5. Increase the drill speed to full once the bit is set
  6. Stop when your bit reaches the other end.
  7. Finish drilling the hole from the other side of the wall for a clean hole

NB: The hole’s diameter will depend on the diameter of the flexible tube. It should be slightly bigger than the flex tube. That will make it easy to push through. I recommended a 2 ½” inch hole saw because I’ve found that it is a good size for most portable generators. 

Now that the hole has been drilled push the other end of the flexible tube through it, from inside the garage. 

6. Find the right PVC pipe size.

Let’s go shopping again. This time, for a PVC pipe. You need a pipe that has the same diameter as your generator’s exhaust. That’s because, just as we connected the exhaust with the flex tube, we will connect the PVC pipe to the flex tube the same way.

Now let’s talk about the required pipe length. Like a chimney pipe, you want a PVC pipe that extends far enough above the roof’s ridge or peak. That’s because we want the fumes from the generator to blow away instead of finding its way back in our homes.

If you need numbers, the pipe should be 2 feet above the highest point of the roof. So, to find the right length of PVC pipe required, measure the length between the drilled hole and the highest point of the roof. 

Take these measurements to help you find out the length of the PVC pipe you need. Take a look at the picture above for reference.

A – The distance between the drilled hole and the roof soffit (or ceiling)
B – The width of the roof soffit
C – The distance between the roof gutter and the roof ridge (or peak)
D – Additional 2ft for proper ventilation

NB: It will be difficult to know the exact distance between the roof gutter and the roof’s peak. However, from the measurements, you will be able to take, and a little bit of guesswork, you should be able to estimate the length.

Also, it’s important to measure the roof soffit width. That is because you will be using a 90-degree pipe elbow fitting to curve the pipe at the soffit.

All of the measurement values added will give you the required length of the PVC pipe.

7. Find the Right PVC Conduit Clamp, Elbow Fitting, and Vent Cap Size

Before you can attach the PVC to the garage wall and successfully install the vent pipe, you need a PVC conduit clamp, a 90 degree PVC elbow fitting, and a PVC vent cap. And they all need to be in the right size. Here is what you need to know.

PVC Conduit Clamp

The conduit clamp’s inside diameter must be the same as the outside diameter of the PVC pipe. Finding a conduit clamp of the same diameter as the pipe will provide a better grip of the pipe to the wall. However, if you find something a little bigger than your pipe, that will work too. But don’t go for a conduit clamp with a smaller diameter compared to the pipe. That won’t work. Here is a huge list of conduit clamps on Amazon for your convenience

PVC elbow fitting

These elbow fittings (Amazon) will be used to connect the pipes. So it’s crucial that you pick the right size. The inside diameter of the elbow fitting must be the same as the outside diameter of the PVC pipe. You can’t buy a smaller sized elbow fitting nor a bigger one. It has to be the perfect size to properly hold the pipes together.

Also, you need to pick up two of these.

PVC Vent Cap

Vent cap will prevent rain and snow from entering the pipe vent but still allow the fumes to be discharged. This is an important part of the whole system. That’s because water getting into your generator’s exhaust will damage it. And you definitely don’t want that to happen.

The inside diameter of the PVC vent cap must be the same as the outside diameter of the PVC pipe. Once again, you need a vent cap that is a perfect fit for the pipes. So look for an option with the same diameter as the pipe.

8. Attach PVC pipe to the wall

Once you have a PVC pipe, it’s time to attach them to our building. Here are the tools you need

  1. Hacksaw
  2. Step ladder
  3. Drilling machine
  4. 1/2 inch drill bit
  5. PVC conduit clamps
  6. 1/2 inch screws
  7. Wall Anchors
  8. Two 90 degree pipe elbow fittings
  9. PVC vent cap
  10. Level

Before you do, you have to cut them in their appropriate lengths to make installation easier. You will depend on the measurements you took in the previous step to cut the PVC pipes.

  • Using a hacksaw, cut the first PVC pipe. This pipe’s dimensions should be length A. That is, the length between the drilled hole and soffit.
  •  Cut the second PVC pipe. It should have the dimensions of length B. That is the width of the roof soffit. 
  • The third and final PVC you cut should be of length C+D. That is, the roof gutter to roof peak length + 2ft

Here is the step by step process of attaching the PVC pipe to the garage wall

  1. Fit one end of the first PVC pipe, labeled A, in an elbow fitting, and place it on the wall, with the elbow fitting at the top.
  2. Measure the PVC pipe and mark every 24 inches up the length.
  3. Using a level, align the pipe to make sure it vertical.
  4. Place a PVC conduit clamp on every marked spot on the pipe and mark the wall through the clamp’s screw holes on both sides.
  5. Drill holes in the marked spots on the walls, using the drilling machine
  6. Insert a wall anchor in each hole drilled, and ensure they are tightly fixed by hammering them.
  7. Place the pipe back on the wall and set the clamps on it. And then position the clamps on the wall anchors. 
  8. Now screw the clamps into the wall with 1/2 inch screws and a screwdriver.

Now that the first pipe is securely attached to the wall, what we need to do next is to connect it to the second pipe, labeled B. This pipe will be right under the roof soffit. When that’s done, fit the second elbow fitting on the other end of pipe B.

The last pipe to connect is the third pipe, labeled C. Before you connect it to the rest, fix the vent cap on one end. And then connect it to the second pipe via the elbow fitting, as shown image above.

9. Connect the Flexible Exhaust Tube to the Vent Pipe

This is the final step to venting your generator. We are done with the most challenging part of the whole process. This will take a few minutes.

To connect the flexible exhaust to the tube to the vent pipe, slide the pipe’s bottom end into the flexible tube. Clamp the flex tube to the PVC and tighten it with a spanner to ensure no leak.

And, you’re done. 

Recommendations

Suppose you were able to follow these steps to vent your generator, congratulations. Here are two recommendations that will help keep you and your family safe while you use your generator. 

Install carbon monoxide detectors in every room

To improve your home’s safety from carbon monoxide, I highly recommend installing a carbon monoxide detector alarm in every room, if possible. Carbon monoxide is a colorless and odorless gas, and you will never know when they seep into your home, putting you and your family’s life in danger. Every protection matters, right?

First Alert Carbon Monoxide and Smoke Detector Alarm (on Amazon) is a two-in-one device that detects both carbon monoxide and smoke in your living area. The reason why I’m recommending this particular device is, it’s battery-powered. So it doesn’t depend on the grid’s electricity or even the generator’s electricity. It operates independently to detect any carbon monoxide in your room. It’s also one of the best-selling and highly rated carbon monoxide detectors on Amazon.

Ventilate your garage

Most garages are not well ventilated because codes don’t require that. I covered this topic in great detail in this article. However, if you are going to run your generator often in the garage, it’s vital to ventilate your garage. That’s because generators produce a lot of heat, making your garage uncomfortable to enter.

There are several ways to ventilate your garage. There are different options to ventilate a garage, such as installing windows or static vents. However, the most effective one I’ve found is installing exhaust fans. 

That’s because most of the different options available rely on air naturally blowing into your garage. On the other hand, exhaust fans force heat out of your garage and replace it with cool air from outside. 

Conclusion

As I mentioned earlier, Option 1 is much simpler, and many homeowners will prefer that option. Option 2 is challenging and involves a bit of work. However, the outcome is rewarding.

Venting a generator in your garage is the first step to keeping your family safe from carbon monoxide poisoning. Do well to implement some of the recommendations to improve your home’s overall safety.