Have you ever walked into a house or room and immediately thought, “Something smells... off”, even though you couldn’t see anything wrong? Maybe you notice there’s a musty, damp smell coming from the basement that doesn’t seem to go away over time, or the attic smells unusually stale and earthy. That persistent damp, musty, earthy odour is often the first warning signs of a mold problem. In many cases, people notice the distinct smell long before any visible growth, making odour a very important clue for early detection.
But why does mold smell so distinct? Why do some people notice it instantly when they walk into a room, while others don’t smell it at all? And can different mold smells give you a hint as to what is going on behind your walls and under your floors?
Let’s break down what causes mold odours, some things it can be mistaken for, and most importantly, what you can do to get rid of the smell safely and effectively.
The classic “moldy” or “musty” smell that is associated with mold comes from something called microbial volatile organic compounds (mVOCs). These are gases that are released by mold as it grows and breaks down organic materials such as wood, drywall, carpet, and even insulation. As mold colonies spread and metabolise, they release these compounds into the air, which is why the smell often becomes stronger over time, especially in enclosed or poorly ventilated areas, like an attic or crawlspace.
Things such as humidity, temperature, and the type of materials mold is feeding on can all influence how strong the smell becomes. Even small amounts of mold growth can produce noticeable smells, particularly in basements, bathrooms and crawlspaces.
Not necessarily, as sensitivity to mold and its smells can vary widely from person to person.
Some people can detect mold odour almost immediately, while others may not notice anything at all, even if they are in the same space. Factors such as age, allergies, asthma, sinus condition, smoking history, and prolonged exposure can all affect a person’s ability to smell mold.
Even if someone can’t smell mold, they can still be affected by it as mVOCs can cause symptoms such as:
This is one of the reasons why relying solely on smell isn’t enough to rule out a mold issue; if one person in a household feels unwell while another doesn’t smell anything, mold could still be present.
Mold doesn’t always smell the same, and the type of odour can sometimes give us cluse about the affected area or the conditions. Some common descriptions of odours associated with mold can include:
While smells alone can’t identify the type of mold, changes in odour strength or quality can signal that a problem is getting worse or spreading to more areas.
While mold has a distinctive smell, it isn’t always obvious to people who aren’t familiar with it, or for those who aren’t sensitive to the symptoms associated with mold. Frequently, mold odours can be mistaken for many household smells, including:
Air fresheners, candles, and cleaning products can temporarily mask the scent of mold odours, making the problem harder to detect while allowing the mold to continue to grow unnoticed.
If a smell keeps returning, especially after cleaning, it’s worth investigating further.
The most important thing to understand is that you can’t truly eliminate mold smells without addressing the mold itself, and its root cause. Here’s what really works:
Mold odours won’t disappear unless the underlying cause of the moisture issue is resolved. This may include fixing leaks, condensation, poor ventilating or past flooding.
Fragrant sprays, deodorizers, and DIY remedies may reduce odours temporarily, however, they don’t remove mold growth. If anything, these will just mask the smell and the problem. Proper remediation involves safely removing contaminated materials and preventing cross-contamination.
Using exhaust fans, dehumidifiers, and having your HVAC properly maintained can help reduce lingering odours, while also prevent conditions that promote mold growth.
HEPA air scrubbers, activated carbon filtration, and professional grade cleaning methods can help remove residual mVOCs from the air after remediation.
If mold smells persist, return frequently, or are accompanied by health concerns, visible growth, or water damage, it’s time to bring in a professional mold remediation team. Mold that is hidden behind walls and flooring, in HVAC systems, and in porous materials can’t be addressed with surface-level solutions.
A proper inspection can help determine the source of the issue, the extent of the problem, and plan for the safest path forward, helping to protect both your health and property.
Mold smells are more than just unpleasant; they’re often your home’s way of telling you something is wrong. While not everyone can smell mold, and not every smell means mold, persistent and unexplained odours should never be ignored.
Addressing mold growth early can prevent costly repairs, ongoing health issues, and long-term damage to the structure of your home. If your space smells off, it may be time to dig deeper, because when it comes to mold, the nose often knows first.
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