What Does Mold Smell Like & How Can You Tell?

Why Does Mold Smell?

Knowing how molds produce odor makes it easier to understand what mold smells like.

As mold grows and spreads, certain gaseous chemicals are produced as byproducts of fungal metabolism.

In scientific terms, these chemicals are called “Microbial Volatile Organic Compounds” (mVOCs). There are over 200 compounds that have been identified as mVOCs, including strong-smelling chemicals such as:

• Aldehydes — i.e. pungent, metallic, starchy, waxy, or sweet
• Benzenes — i.e. the smell of gasoline
• Toluenes — i.e. the smell associated with paint or paint thinners
• Ethanol — i.e. the smell of hand sanitizer
• Ketones — i.e. the smell of nail polish remover, overripened fruit, or metal
• Esters — i.e. sweet and fruity like ripe bananas
• Carboxylic Acids — i.e. sour, tart, often unpleasant, and sometimes downright rancid
• Lactones — i.e. milky, creamy, sometimes fruity
• Terpenes — i.e. pungent smells ranging from citrusy to cheesy to skunky
• Sulfur & Nitrogen Compounds — i.e. rotten eggs and ammonia

The exact chemical makeup of mVOCs given off by mold varies depending on the species of mold and where it is in its life cycle. As a result, the smell of mold might be different each time, making it tricky to identify with certainty.

If you’ve detected a strange odor in your home, here are some signs that it might be due to mold.

What Does Mold Smell Like?

Most people describe the smell of mold as musty, stale, and earthy — somewhat similar the odor of wet socks or decaying wood.

Although mold smells can vary, here are some of the most common characteristics:

• Musty and Stale — like old socks or a stuffy attic that hasn’t been aired out in months
• Earthy — like a dense forest, rotting wood, or the dirt underneath decaying leaves
• Damp — like wet dog fur or a dank locker room
• Rotting or Fermenting — like aging cheese, decaying fruit or fermenting alcohol
• Sour and Tangy — like armpit odor after a vigorous jog

The smell of mold is usually quite foul and unpleasant, and it grows stronger over time as the mold starts to spread and sporulate.

“Musty” and “stale” are the most accurate descriptors of what mold smells like. The musty odor is a result of the hodgepodge of mVOCs produced by the mold and released into the air.

In addition to mustiness, mVOCs are also responsible for notes of earthiness, rotting, or sourness.

Dampness is another common theme, as mold often follows water or moisture issues in your house or apartment. Mold needs excess moisture to grow, which is why the scent of dampness or humidity always accompanies mold odor.

Similarly, severe mold and moisture problems can lead to rotting and decay of organic materials that make up the surfaces where mold grows. Common examples of such surfaces in your home include wood, drywall, and fabric.

The typical bathroom mold or mildew found growing between shower tiles don’t typically smell like rot, but severe mold growth on walls and ceilings — especially after a flood or leak — can make room smell like rotting wood or fermented cheese.

Household Odors Similar to the Smell of Mold

While mold is the most common indoor air quality problem that leads to strange malodors in your home, there may be other suspects as well. Here are some other household smells that might be mistaken for mold:

A mild, unpleasant odor in your house or apartment could also be from:

• Wet or dirty laundry
• Kitchen and bathroom garbage
• Bad food odors from the fridge, garbage disposal, dishwasher
• Pet odors
• Rodents or other pest issues
• Natural gas leaks
• HVAC problems
• Sewage backup

How Can You Tell if You Have Mold?

The only way to be 100% certain that you have a mold problem creating unpleasant odors in your home is to find the source.

Mold growth that is severe enough to create odor is visible to the human eye. However, it can be difficult to spot depending on where it’s located — for example, behind furniture, under carpeting, and inside walls.

If you’re not sure where your mold smell is coming from, read our article: How to Check for Mold in Your House or Apartment.

In addition, here are common signs or risk factors that may point to mold:

• You recently had moisture problems (e.g. floods, leaks, humidity, or condensation around windows and vents).
• You or your family members are exhibiting symptoms of mold (e.g. allergy-like responses while indoors, sneezing, runny nose, skin rash, difficulty breathing, skin rashes, fatigue, malaise).
• You see peeling paint or wallpaper (mold growing on wood or drywall underneath can cause paint or wallpaper to deteriorate).
• The smell is stronger when you have air conditioning on (standalone AC units are prime spots for mold growth).
• You use a humidifier constantly (the excess water vapor can lead to mold growth).
• You live in a newly-constructed home (due to jobsite storage problems, improper insulation installation, or poor construction practices).

If you aren’t able to visually confirm the presence of mold, despite smelling abnormal, mold-like odor in your home, consider hiring a professional mold inspector.

Mold inspections involve a detailed investigation for the presence of mold in your house or apartment, covering hard-to-reach areas that you might not have thought of. Moisture sensors and other tools are also used to help detect mold growing behind and beneath other surfaces.

If any mold is found, the inspector will provide you with a detailed report along with a recommended plan for mold remediation. Samples may be taken for testing, although this is not usually necessary according to the EPA.