🧂 Put a Glass of Salt in Your Car — Here’s What It Can Actually Do

You may have seen this viral tip claiming that every driver should keep a glass of salt in the car, supposedly after a police officer recommended it.

There is a little science behind the idea—but the viral version makes it sound more powerful than it really is.

🚗 Why Would You Put Salt in a Car?

The main reason is moisture.

When the inside of a vehicle contains humid air, that moisture can condense on the cooler windows and windshield, creating the familiar foggy appearance. Wet shoes, clothing, umbrellas, carpets and even normal breathing can add moisture to the cabin. AutoZone.com

Salt can interact with moisture in humid air. Ordinary sodium chloride begins absorbing enough moisture to form a liquid solution at relatively high humidity, around 75% relative humidity. Canada

So, yes—the chemistry behind the trick is real.

But there is an important catch: a small glass of ordinary table salt has limited moisture-absorbing capacity. It isn’t equivalent to a proper automotive dehumidifier.

🧂 Does It Really Stop Foggy Windows?

It may help a little, particularly in a mildly damp car that’s parked overnight.

However, if your windshield is constantly fogging up, don’t assume that adding salt has solved the problem.

Persistent moisture can be caused by:

Wet floor mats or carpets
Water entering through damaged seals
Blocked drains
A clogged air-conditioning drain
Wet clothing or umbrellas
Excess humidity trapped inside the vehicle

If the underlying source of water isn’t addressed, a small container of salt won’t be able to keep up. AutoZone.com

⚠️ One Thing I Would Change About the Viral Tip

I wouldn’t recommend leaving an unsecured glass of salt on the dashboard or seat.

A sudden stop or sharp turn could send the glass flying. And if salty moisture or saltwater spills onto metal or electrical components, that’s not something you want inside your vehicle.

If you want to experiment with a moisture absorber, use a stable, sealed or purpose-designed container and secure it so it can’t move around.

Commercial automotive moisture absorbers commonly use materials such as calcium chloride or other moisture-absorbing materials, which are designed specifically for this job. NAPA Blog

🌫️ What Should You Do When the Windshield Is Already Foggy?

This is much more important than the salt trick.

Don’t drive until you can see clearly.

For interior condensation:

Turn on the defroster/defogger.
Use fresh-air mode rather than continuously recirculating the humid cabin air.
Turn on the air conditioning, if available—it helps remove moisture from the air.
Direct airflow toward the windshield.
Make sure wet mats and other damp items are removed or dried.

Using the A/C with the defroster can help dehumidify the cabin and clear the windshield more effectively. Consumer Reports

🧂 So, Is the Salt Trick Worth Trying?

Think of it as a small moisture-control trick—not a miracle car hack.

A little salt may absorb some moisture under sufficiently humid conditions, but it won’t repair a leak, replace your defroster, or guarantee a fog-free windshield.

And the claim that a police officer specifically taught this trick isn’t something I can independently verify from the image.

The most useful lesson is this: if your car repeatedly becomes damp or foggy, find out where the moisture is coming from.

🚘 Bottom Line

A glass of salt isn’t a secret safety device, but the basic idea has some chemistry behind it. Salt can take up moisture under humid conditions, although ordinary table salt is a relatively limited moisture absorber.

For serious or persistent condensation, proper ventilation, a functioning A/C/defrost system, dry carpets and mats, and fixing water leaks are much more important. TÜV NORD

Have you ever tried putting salt—or another moisture absorber—in your car? Did it actually make a difference? 🧂🚗