Litter Box Vent Fan - Eliminate Cat Litter Stink




About: Daniel Bauen breathes new life into objects that have met their untimely demise in the junk pile.

CAUTION: Following these simple instructions may lead you to forget that you own a litter box, and therefore neglect to clean it. Please proceed with care.

I despise the smell of litter boxes. Even when cleaned well, the smell of cat litter can be overwhelming. It's ok if you live in a large house where you can dedicate a utility room, garage, or basement to the litter box. In an apartment, it is often impossible to keep a litter box out of smells reach.

For that reason, I made this simple litter box exhaust, which draws a small amount of air out of a covered litter box, and blows it outside. The computer fan draws just enough air to keep odors from escaping the box. The hot/cold air loss to the exterior seemed to be pretty minimal, because there is no noticeable change in heating/cooling costs. It works so well that people would be surprised that there were cats in the apartment.

The computer fan is rated at 0.13A, so it could easily be run off batteries being charged from a small solar panel outside. This instructable shows how to do just that:

Cats are generally freaked out by noise and weird stuff in the litter box. The fan is so quite, and far enough away from the litter box, that the cats did not care in the least bit. They were actually a little curious as to the dryer hose sticking in the box.

I built this system years ago, but was prompted to put it up after seeing this:
The bathroom fan seems like overkill, especially considering the fact that they cannot leave it on all the time.

See more cool projects at:

Step 1: Materials

1. Computer Fan
2. Plastic dryer hose
3. Sheet of Lexan
4. 2 Plastic cups that fit about 3/4 of the way into the dryer hose
5. Outdoor electrical junction box (which computer fan fits inside of)
6. Screws
7. Glue
8. 12 Volt wall power adapter

Step 2: Fan Box Construction

The fan housing consists of an electrical utility box.

1. Cut a square hole in the bottom of the box to accommodate the size of the fan.

2. The fan is mounted to the back using screws at the corners of the hole.

3. Since the back of the box will be facing the exterior, a screen is placed across the hole to prevent the entry of bugs.

4. A circle is cut in the cover of the electrical box (fan box) to accommodate one of the plastic cups.

5. Cut the bottom off the plastic cup, and push the cup through the hole of the electrical box cover. Glue in place.

Step 3: Mount Fan Box in Window

I mounted the fan box in a sliding window. There are many other ways to mount the fan box. If you want it to be permanent, you could just mount it through the wall using standard dryer fixtures. This just gives you an idea of one way to do it.

1. Cut a piece of Lexan to the appropriate size to fit in the window.

2. Cut a square hole in the Lexan. The hole should be the same size as the hole that was cut in the electrical box. I only cut 3 sides of the hole, bending the center piece out to create a mini awning to protect the fan from rain, etc.

3. Screw the electrical box to the Lexan window.

4. Mount the Lexan and fan box assembly in the window. (The pictures below show it with the dryer hose already installed)

Step 4: Install Dryer Hose on Fan Box

Slide the dryer hose over the plastic cup. It should get tighter as you slide it up further. Apply tape if it is too loose to stay on.

Step 5: Install Dryer Hose in Litter Box

1. Cut a round hole in the litter box lid. You should be only able to slide the plastic cup 3/4 of the way in. This will allow you to wedge the dryer hose in between the cup and the hole.

2. Pass the end of the dryer hose into the hole in the box.

3. From the inside, push the plastic cup into the dryer hose. Push far enough to wedge it tightly.

4. I covered the top of the cup with a screen to try to keep cat hair out of the fan. You could also use a filter, because the dust still goes through the screen. But the dust never damaged the fan, and computer fans are cheap.

Step 6: Power It Up, and Test It Out

To power the fan, use a 12 Volt power adapter, and connect the leads to the computer fan leads.

Hope this improves your air quality, and leads to a healthier life. Enjoy!



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    46 Discussions


    10 years ago on Introduction

    Hi, My friends who have 10 cats (they use to own a cattery) have actually made a product called "LItter Vent" that absolutely works. You would never know that they have 7 cat litter boxes in their house. I'm not just saying this to promote them. It really does work. The only time you'd ever notice any cat box odor is when one of the fans stop working. It's available online, if anyone is interested. They sell it as a kit. Hope this helps anyone who's feeling desperate and can't take the smell any more.

    2 replies

    Reply 8 years ago on Introduction

    Thank you for this information, since putting together this instructable solution would require me to be more handy than I am. I found the website and plan on ordering one to try it out.


    Question 6 months ago

    This is a great idea, i currently have my cat's box in a spare room upstairs and currently will be moving it to the basement. Couple questions though, I have a couple floor drains in my basement and the house is relatively new so the basement is very water tight and dry. With the two floor drains could i just fasten the one end of the hose to the drain rather than modify one of the windows? I could place tape over the other drains to block the smell and the scent would just carry on through the pipe to the street. Just an idea and want to know what you think. Also is the fan running continuosly or is there a motion sensor whenever the cat drops a load? Thanks


    Reply 3 years ago

    It is a very old idea, at least as old as the litter box itself. We had one in the early 70's , same thing as in the picture but not enclosed. It was a hooded tray. Hooded or enclosed it really is worth the effort to make one and it hardly cost anything.

    Over the years since than we have found some cats never get used to the fan sound and will poop in the sink, bathtub or your bed instead :)


    Question 1 year ago on Step 1

    How long of a distance can you have the vent hose entry to litter box away from the exiting point at the window? Will the fan at the box be strong enough to exit the odors about 10-15 feet to the window? Thank you for the system you came up with and your response to my question.


    3 years ago

    How exactly do you cut the square and circle out of the junction box? What tools are you using?


    3 years ago

    PS, feline pine and yesterdays news are great products but one of our cats was declawed by the previous owner and she WILL NOT use anything but regular liter. I also have a toilet shaped box that is great but she again, wont use that either. If it wasnt for the elderly declawed cat we probably wouldn't have an odor problem.


    3 years ago

    That's awesome! I just had the idea for this and I always look online to see if someone already did it since I know most thoughts are not unique so maybe I could get an idea and vwala, here it is. My cat box is terrible and the smell permiates the house regardless of how often I clean the box. My cats are the stinkiest cats I know lol


    10 years ago on Introduction

    I've got three cats. To say litter/odour control has been an issue is an understatement. I've gone through all sorts of contraptions from automatic rake systems to macerating cat toilets. This is a clever idea, but may not be suited well to multi-cat households where several boxes are required. I solved my problem with a simple change in litter formulation. I found a wheat-based litter that claims the natural enzymes break down the stank, and it does a great job. It doesn't clump well and one of the three won't use an all-wheat box, so I've found a mix of 1 part clay litter to 2 parts wheat litter is the perfect medium between happy cats, easy cleanup, and odour control. The only time I smell anything is if they don't bury it, which usually means I've missed a cleaning so I take that as a feline post-it note to clean the box.

    1 reply

    10 years ago on Introduction

    what if you were to attach the hose to a dyrer, so when the fan is on the air from the litter would escape through the dryer hose and ergo outside. however you would have to create a device that would allow air to leave the dryer but not allow cat litter air to stink up your clothes that are just sitting in the dryer.....hmmmm...

    2 replies

    Reply 10 years ago on Introduction

    Just put a sort of a check valve on the dryer end of the "T" and I t would work...


    9 years ago on Introduction

    My dad has a patent on the similar thing he made years ago.  hasn't made any money on it yet though.

    1 reply

    5 years ago on Introduction


    Thanks for sharing these valuable information.

    We know litter box is an indoor feces and urine disposal box for cats. And it is really helpful for cleaning my house form the bad smell of my pets. It is really useful and wroth of money.

    Thanks for your design it's really helpful.


    7 years ago on Introduction

    I built one out of plywood and used a range hood with fan and light,
    the cats had a light for night use and the fan runs constantly on low venting outside through a separate vent in the wall.
    total cost under $50 including new wood and vent tube and used range hood.