Garage Air Filtration

Dog poo is the Houdini of icky smells. You can handcuff it in a tight bag, upside down in a tank of water, and it will still escape. The worst stink in my garage is the dog poo pail, but the fix is easy.

The likely cause of garage smell in most garages is mold, mouse droppings, garbage stink, dog poo and cat urine. The dog and cat smells are easy enough to find. The mouse droppings might be in the wall. Fixing the mold smell is the most important to your health.

Dog poo has an obvious smell. Cat urine smells like ammonia. Mold smells like a decomposing magic marker. Mouse dropping smell like the oldest house you’ve ever visited.

Why the Garage Stinks

When was the last time you cleaned the toilet or kitchen floor? Now compare that to the last time you cleaned anything in the garage? Even organizing the garage is not cleaning it. At least with bleach, vinegar, baking soda or a vacuum.

Have you ever cleaned the garage floor this well?
Have you ever cleaned the garage floor this well?

Mice, Chipmunk and Bat Turds

Meanwhile, critters are seeking warmth and territory. Your garage is easier to enter than your home. They’ll take it.

Critter such as mice, bats and chipmunks setup home in stored furniture and insulation (if you have an attached garage, there’s insulation in the wall where the house and garage meet). These critters pee and poop. That stuff stinks.

Brown bat
This mouse is actually a bat. It poos and pees on your garage as easily as a mouse does.

The Dog Poo Pail

Then there’s the poo pail. Do you “curb” your dog? Do you pick up the poo and bring it home for all to admire? We do. Our poo pail is a masterpiece of garage stink. I wash and disinfect the can to fix the smell. One is not enough. I wash it AND I Lysol it to reign in the stinky contents.

Which can is the dog poo pail?Car Exhaust

I know you’re not trying to commit suicide, but that doesn’t mean you’re not succeeding. Car exhaust is full of carbon monoxide. When it gets in your blood, it prevents you from getting the oxygen you need to live. Car exhaust isn’t just stinky, it’s deadly.

Air out garage exhaust
Air out garage exhaust


Mold has a quick, sharp smell similar to the ink from an erasable board pen. Don’t ignore the mold smell. Pick up and fix it right now. It’s dangerous, and it will only get worse. Read more below.

Woman incorrectly cleaning mold on a wall.
This is NOT how to clean mold. She should be wearing googles and a mask. Mold is dangerous.

Why You Should Air Out Your Garage

The easiest way to clean airborne stink is to air out the garage. Anything that’s active in the air, such as car exhaust, is easy to “clean” by getting rid of it.

Air Out Car Exhaust

Air out car exhaustI admit that I warm up my car in the garage, despite the fact that this once caused a carbon monoxide emergency at my house. We had a very cold winter, so I did not want to pull into the driveway to warm the car. The problem was that the colder the air outside, the more exhaust will stay in the garage. Air out the garage to remove dangerous (deadly) carbon monoxide from the car exhaust.

Air Out Dangerous Gas

Air out the garage if anything is out gassing. Old-fashioned pegboards have formaldehyde inside, as an example. The gas is encapsulated in the outer material, but it is dangerous if that material is exposed. Anything that smells when you get it is out gassing. If you can leave an out gassing item outside until it clears, all the better. If you store it in the garage, then air the garage out to remove the danger.

What is in your garage that might be putting out a dangerous gas? Any new product made of plastic will probably outgas for a few weeks. Smelly plastic is dangerous. A little volatile chemical here, a little volatile chemical there, the next thing you know, it’s causing a disease. Plastic smell can cause nausea, sore throat and coughing. Airflow is your best friend.

How to Air Out the Garage Quickly

The quickest way to air out the garage is to put a few high-power fans in the window or the door. Face the fans outward, to pull the air from the garage to the outside. Fans cannot get everything, but using a simple box fan is the fastest way to move fresh air into the space.

Use a fan to air out the garageRemove big offenders from the garage, wash them, and put them back. The offenders in my garage are the garbage cans. The one dedicated to bags of dog poo is a real flycatcher. Wash the garbage cans twice a summer. Use a bucket of water with dish soap and a large sponge or a terry cloth. I like the pack of 50 terry cloths you can get at Costco. Don’t put the cans back until they are dry.

How to Clean Garage Air

I started this article thinking I needed an air purifier to remove garage odors. Now I realize that an air purifier might not do the job. There might be a more effective and cheaper option, so let’s do this in order.

One of the best air purifiers is a box fan with filters. It’s a do-it-yourself project that looks like this: Better Box Fan Air Purifier

Tom Builds this fan with two air filters

I love the way Tom built that fan air purifier because he recognized the one thing most articles on the subject do not. Fan motors are designed to pull air, not to filter it. The filters taped to the fan require the fan to work harder to pull the same amount of air it would without the filters. When the motor works harder, it has the potential to burn out.

By using two filters angled into a pyramid shape, the fan has a higher air to filter ratio. There is more air behind it so it does not have to work so hard to pull the filtered air through the blades. This is a great tutorial, here is the link again: Better Box Fan Air Purifier

Best Garage Air Filtration System

You do not feel like making your own fan filter, and you want to buy a garage air filter. The best air filtration system is big, has a HEPA filter, has a carbon filter, and has a VOC filter.

When you size your garage air filter, remember that the ceiling adds lots of volume to your measurement. Manufacturers measure air purifiers based on rooms with 8 ft. ceilings.

To compensate for the garage’s extra volume, double the “ACH” value on the purifier box. The ACH value represents the air changes per hour. If your garage ceiling is 16 ft., you will need twice the recommended ACH.

The carbon filter does the heavy lifting. It grabs odors, dust and smoke. If you can see it then the carbon filter should absorb it. The VOC filter is also a carbon filter. To filter VOCs, the carbon filter has to be porous, more porous than the typical purifier carbon filter. A porous filter can remove formaldehyde, plastic out gassing, benzene and polyurethanes.

HEPA removes the tiniest of particles. It might be overkill in a garage as its best function is to help with allergies. HEPA is good at removing particles less than .3 microns. That includes pollen, dust, mold and bacteria. The best HEPA filter has a MERV value of 16. This is the one that filters down to the smallest particle size.

Garage Mold is the Most Dangerous Smell

You should know how to find, kill and then prevent garage mold. The dog poo smell might be worse, but the mold smell is the most dangerous to your health. Poo hurts your face, but mold hurts your whole body.

Measuring wall moistureMold has a pungent smell; it hits you right in the middle of the head. It’s similar to the marking pen scent. Mold smell wafts into your forehead before you really get a hold on it.

Get moving on this smell because the longer you wait, the worse it gets. You have nothing without your health, so find, kill and then prevent garage mold. Learn more in my article, Find, Kill and then Prevent Garage Mold  (the link opens my Reboot My Garage article in a new window)

Storing Furniture or Have Insulation? Look for Mouse Turds

You’ll have no problem tracking down the poo stink, but what about that subtle smell you can’t quite finger? If you’re storing any furniture in the garage, you might smell the wafting grace of mouse turds. Mice love the garage because it is easy to get in and get warm there.

Make the garage unattractive to mice, and then clean out their nests. Mice take up residence in insulation and furniture. If you have ever been in an abandoned house, you will know the scent.

Mice will find this dog food
Mice will find this dog food

Remove anything that attracts mice in the first place, including:

  • Remove food. All food is mouse food. They eat anything.
  • Clean stinky, dirty trashcans that act as a beacon for every mouse nearby.
  • If the firewood is in or near the garage, then mice are in or near the garage.
  • Seal the gaps. Everything 1/2 inch and larger is a mouse portal to your garage.

Clean the mouse homes, but do it safely:

  • Mice carry diseases. Use a mask that covers your mouth, nose and eyes.
  • Mouse turds are unsafe for the same reason. Use rubber gloves as well.
  • Remove the nest and droppings.
  • Clean away the urine and turds using 1 tsp bleach per quart or water. After it’s dry, spray disinfectant on the area and leave it there, don’t wash it off.

How to Get Rid of Cigarette Smoke in the Garage

Getting rid of smoke and getting rid of the smell are two different things. The smell is in the air with the smoke. The smell is also on the walls where tar sticks.

To clean the air, use vinegar, baking soda and a fan. Use white vinegar to clean surfaces of smoke particles.

Air Out Smoke

Use a strong fan to pull air out of the garage. Position the fan at the window or door facing outward.

Absorb Smoke Particles

Air out tobacco smokePut bowls of baking soda around the edges of the garage. The baking soda absorbs smoke. Spread baking soda on soft materials such as garage mats. Leave the bowls out for at least a day, longer if the smoke smell is heavy. Vacuum the mats after a day or two.

Do the same with vinegar as you did with baking soda. Put several small bowls of white vinegar around the edges of the garage.

Neutralize Tar Stuck to Surfaces

To clean the surfaces, either recycle the vinegar you just used, or get fresh. Put the vinegar in a spray bottle. Wet the surfaces with the vinegar. Rough surfaces will just soak it up. You can wipe down wood with a terry cloth. Repeat until the cloth is clean after wiping the area.

How to Get Rid of Garage Cat Smell

That cat smell is from poo and urine. If the litter is in the garage, empty the box into a plastic bag. Then air out the garage. If the poo and pee is coming from a stray, take the same measures as you would with mice. Clean the area, and get rid of what the cat finds attractive. Seal the gaps.

Use Baking Soda and Vinegar to Neutralize Urine

Cat urine has the same acidity as cigarette smoke. The baking soda and vinegar that works on cigarette tar will work for cat urine. Air out the garage with bowls of baking soda, bowls of vinegar, and a strong fan pointing outward.

Cat waiting to get into the garage

Use Dish Soap and Hot Water to Wash Dirty Spots

Wash urine spots with soap and water. You might be tempted to bring the hose into the garage to wash things down. Unless you have a massive air out fan, you’ll end up with sitting water. Water leads to mold, so don’t chance it. Rinse the soap and water, and allow to dry.

Use Vinegar to Neutralize the Urine Acid

Once the hard surfaces are truly dry, spray with a mixture of white vinegar and water. Use two cups of water to one cup of vinegar. I put mine in a spray bottle. You could use a chemical sprayer, too, if it’s clean inside.

Spray the cleaned and dried urine spots with a coating of vinegar spray. Allow it to soak in. Don’t wipe or clean the vinegar away. It neutralizes the uric acid causing the smell.