how to get rid of mildew smell in car

Musty, damp smells are distinctive and annoying, but can also be a health hazard. We will look at what causes mildew and how to get rid of musty smells.

Mildew is a type of fungus, different to mould in that it is commonly white. But you probably don't need to visually identify it, as you can usually smell it before you ever see it.  If your car has the right conditions for mildew, you probably have other forms of mould and fungus too, which all adds up to give you that musty old smell.

What causes mildew in cars?

Mildew requires food, water and warmth in order to grow.

There is always going to be food for mildew in your car, no matter how much you clean it, as it only needs trace amounts. You will be trampling dead leaves into your carpets, there is plenty of organic matter in the dust in the air, and the oils from your skin are enough to create a biofilm for mildew to grow, which is why it's often most evident on seat belts and seat edges.

It needs high humidity, and won't grow unless there is moisture in the car. It also likes to be quite warm, which you might find surprising as most people associate it with the cold.

When you aren't using the car, the car gets cold, the water drops out of the air and condensates on surfaces where there is a biofilm that mildew spores can grow on. You use the car again, warm it up, make it humid, and then the mildew can grow. Then, when you aren't using the car, it gets cold again it cools down which inhibits the growth of the mildew, but it pumps spores into the air. So when you get into a cold car with still air it you get that horrible damp smell.

Is mildew dangerous?

It's not ideal. Some people aren't much affected, others can have an allergic reaction causing a runny nose, watery eyes, itchy face and wheezing and shortness of breath. It can be a problem for people with asthma, and also young children, old people and anybody with underlying health problems.

We would recommend taking it seriously because in our experience in dealing with cars with mildew and musty smells, we are highly likely to find visual traces of other moulds and fungus, and the ideal conditions for growing mildew are also good for bacteria and germs, all of which can be more dangerous.

• Can damp and mould affect my health? - NHS
• Basic Facts about Mold and Dampness - CDC

How to remove mildew in a car

Water - Leaks in cars

The main problem, and the one you must address first, is excess moisture in the car.  We see a lot of cars with mould and mildew because we fix cars with leaks. There are a few other reasons why your car could be damp, but in the vast majority of cases your car will have a leak. 

You are probably finding that you have steamed up windows, you may even find you have some electrical problems, such as electric windows being temperamental or warning lights on your dashboard. Water ingress can cause much bigger problems than mildew, and you are never going to remove damp smells if you have several gallons of stale water under your carpets. So, you need to check your carpets and in the boot to see if there are any signs of leaks.

If you do have a leak, you need to get it repaired and the car needs to be dried thoroughly. There are not that many ways for water to escape your car, and there could be far more water than you think. It is not uncommon for us to pull a couple of gallons out of a car with a leak, and this will not dry out by driving around with the heater on or windows open, not before it can cause other problems.

Food - Keep your interior clean

Having your car cleaned will remove organic matter that mildew can grow on. There is actually very little of the car that is inviting for mildew, and it won't grow on carpets or seats which are synthetic fibres, nor will it grow on plastic surfaces.  We most commonly find white moulds in the back of estate cars that transport dogs, as animals have oils on their fur which will transfer to carpets.

Having the car shampooed will remove most of the organic debris and biofilm, which can act as a substrate for fungus. Even better is to treat the car with a product which is anti-fungal, antimicrobial and anti-bacterial. As well as killing the mildew and it's spores, it will treat any organic matter which has found its way deep into your carpets and fabric, making an environment which is toxic for fungus. 

Warmth - Use the car

It does seem to be the case that mildew appears in cars that are not used very often or have been parked up for a while. If you are getting mildew on your second car, the one that only usually does the school run, we recommend giving the car a run every few weeks, going on a journey where the engine gets a chance to warm up, put the heater on, open the windows, get the air circulating.

The engine will thank you for it too, but it does seem to be the case that the more you use the car, the less likely you are to suffer these problems.

Getting rid of the smell

What do you smell? Are there spores of mildew and other mould and fungus? Giving the car a good vac and shampoo, treating with an antifungal, and giving the car a good airing out will help get rid of this. Once the mildew has been killed and removed, it shouldn't be producing any new spores.

How to remove that old car smell

There is more to an old car smell than just mildew, I have also heard it described as an 'old man smell', which is often associated with classic cars, which have less plastic and far more organic materials such as hemp, fibre board and leather involved in their construction. This can mean the car can smell a bit old and musty. Like old books, some people quite like the smell, but others can't stand it. There are things that can be done to reduce it, and replace it with something like a new leather smell.

If you get this smell on newer cars, a good clean, especially steam cleaning can work wonders, followed up with deodorizers. 

Does baking soda remove the smell?

Baking soda can certainly help, and it is something we would use, although we might use a more sophisticated version such as odour absorbing crystals or granules. However, it is not a magic bullet.

A while ago, I acquired an antique razor that came in a wood and leather box, which stank like stale water. I sealed it in a bag with generous amounts of baking soda and the smell went eventually, but it took two years. So sprinkling a bit of baking soda on or under your car's carpets is unlikely to remove that odour on its own. Most people believe that baking soda absorbs smells much like activated charcoal, and it does to a minor extent, but it actually works because it is a fungicide and disinfectant. Products like Shake n' Vac do something similar, but better. You can actually use activated carbon if you wish to absorb the odour, some people put bags of it in the door pockets, or if you have the carpets up because you are drying out after a leak, you can sprinkle granules of it under there. This is more effective at pulling odours out of the air, but isn't a magic cure (video related) and as we have said in our Honest guide to removing car odours, removing odours is not rocket science, but often far more difficult than you might think.

Do Odour Bombs work?

It depends on the type of odour bomb. Those that put a smell into your car might hide the smell, but they don't do anything to solve the problem. And so, after the fragrance has worn off, you are back to square one.

During the COVID epidemic, several companies produced products that spray a disinfectant into the air, these will certainly make a difference. 

If you are wondering what an odour bomb is, it is an aerosol spray which, once set off, keeps spraying until the can is empty. You set it in your car, pull the fuse, then close all the doors. It will spray its contents into the air, filling your car with a fine mist of the product. If you can find one which is a disinfectant, then we would certainly recommend it. But you will still have to fix any leaks, dry the car, clean the car and follow all the other steps if you are to prevent mould and mildew in future.