How Dehumidifiers Prevent Mould Growth After Water Damage
By: Brothers Equipment & Supply
After any form of water damage—whether from a burst pipe, flood, or appliance leak—moisture lingers in the air and within building materials.
If left unchecked, this moisture creates the ideal environment for mould growth. Dehumidifiers play a critical role in the drying process by removing excess humidity and helping to restore a healthy, safe indoor space. They are not just helpful—they are essential.
Let’s get right into it!
Mould begins to grow alarmingly fast. According to Health Canada, mould spores can become active in as little as 24 to 48 hours after moisture exposure. Once established, mould spreads quickly across surfaces like drywall, wood, and carpets. Rapid intervention is the only way to halt this process.
Mould thrives in environments with high humidity (above 60 percent), organic material, and low airflow. Wet walls, floors, and ceilings provide the perfect breeding ground. Even seemingly dry surfaces can harbour moisture deep inside, making them susceptible to hidden growth.
Humidity is a major driver of mould development. When indoor humidity levels are not controlled after water damage, spores settle and begin colonizing within hours. Keeping humidity below 50 percent is one of the most effective ways to stop mould before it starts.
Dehumidifiers pull moisture from the air using either condensation or desiccant processes. Refrigerant models cool the air to condense water vapour into liquid, while desiccant models use absorbent materials. Both types significantly reduce indoor humidity and speed up drying.
Most modern dehumidifiers allow you to set a target humidity level. For post-water damage recovery, aim for 30 to 50 percent relative humidity. Built-in sensors maintain this range automatically, helping to prevent moisture levels from rising again.
To maximize their effect, dehumidifiers should be placed centrally in the affected room, away from walls and furniture. Keep doors and windows closed to prevent outside humidity from interfering. Using them alongside fans or air movers helps circulate air and extract moisture evenly.
Dehumidifiers remove water not only from the air but also from porous materials. They help dry out drywall, wood framing, insulation, and flooring far more quickly than air circulation alone. Faster drying reduces the chances of permanent damage or rot.
Even after visible water is removed, high humidity can continue to damage your home. It causes wood to warp, paint to blister, and adhesives to weaken. A dehumidifier keeps conditions stable, preventing these secondary issues from emerging weeks later.
By reducing moisture, dehumidifiers also reduce airborne mould spores and bacteria. This improves overall air quality and makes your home safer for people with asthma, allergies, or respiratory sensitivities. Clean, dry air is essential for long-term health and comfort.
Choose a dehumidifier based on the size of the room and the amount of water involved. A small, damp room may only need a 30-pint unit, while a large, heavily saturated area may require a 70-pint or industrial model. Proper sizing ensures effective performance.
Residential units are designed for single rooms or mild humidity issues. For severe water damage, commercial dehumidifiers offer faster moisture removal and larger capacity. Restoration professionals often use high-capacity units to manage multi-room drying projects.
Some dehumidifiers come with built-in pumps for continuous drainage, digital humidity controls, and auto-restart functions in case of power outages. These features allow for round-the-clock operation and simplify the drying process, especially in large spaces.
Dehumidifiers work best when combined with air movers and heaters. Air movers direct moisture into the air, where dehumidifiers capture and remove it. Heaters raise the temperature slightly, increasing evaporation. This trio is the standard setup in professional restoration.
Use a hygrometer to track humidity levels throughout the drying process. Place sensors at various heights and locations in the room to detect moisture pockets. Consistent readings in the 30 to 50 percent range indicate effective drying.
In the early stages, continuous operation is necessary. Dehumidifiers should run non-stop for the first 24 to 72 hours after water damage. Once moisture levels are under control, you can switch to intermittent use or shut the unit off entirely if the space remains dry.
Why Is A Dehumidifier Important After Water Damage?
Dehumidifiers remove excess moisture from the air and materials, which helps prevent mould growth and structural damage. They speed up the drying process significantly.
How Fast Can A Dehumidifier Prevent Mould?
If used immediately, a dehumidifier can reduce humidity enough to prevent mould from forming within the 24–48 hour danger window. Early use is critical.
What Humidity Level Stops Mould From Growing?
Keeping indoor humidity below 50 percent prevents mould spores from activating. For best results, aim for a range between 30 and 50 percent during drying.
Can I Use A Household Dehumidifier After Flooding?
You can use a household unit for minor water damage, but severe flooding often requires commercial models with higher moisture removal capacity.
Where Should I Place A Dehumidifier In A Flooded Room?
Place it centrally, away from walls and obstructions. Ensure good airflow around the unit and close doors and windows to keep outside humidity out.
How Long Should I Run The Dehumidifier After Water Damage?
Run it continuously for at least 24 to 72 hours or until humidity levels return to normal. Use a hygrometer to determine when the room is fully dry.
Are Dehumidifiers Alone Enough To Prevent Mould?
Dehumidifiers are essential, but they work best when combined with fans and proper ventilation. For large jobs, a complete drying strategy is necessary.
What Is The Difference Between A Dehumidifier And An Air Purifier?
A dehumidifier removes moisture from the air, while an air purifier removes particles like dust, allergens, and pollutants. Each serves a different purpose.
Do I Need Multiple Dehumidifiers For Large Spaces?
Yes, large or multi-room areas may require more than one unit to ensure even drying. Restoration professionals often use several devices at once.
How Do I Know When It Is Safe To Turn Off The Dehumidifier?
Use a hygrometer to check if relative humidity stays between 30 and 50 percent for at least 24 hours. If the room remains dry, you can safely turn it off.
Dehumidifiers are a vital part of the water damage recovery process. They remove moisture, prevent mould, and protect the structural integrity of your home or business.
Whether you are handling a small leak or a large flood, using the right dehumidifier—alongside proper drying tools—can make the difference between a quick recovery and a long, costly restoration. Do not wait until problems appear—act fast, dry thoroughly, and breathe easier.
If you have any questions about our article “How Dehumidifiers Prevent Mould Growth After Water Damage” or need water damage equipment contact us at sales@brothers-equipment.com or connect with us on social media.
Drying Rooms Quickly After Flooding: What You Need To Know Flooding can turn any room…
Portable Dehumidifiers Vs Industrial LGR Dehumidifiers: Main Differences, Pros And Cons By: Brothers Equipment And…
How To Position Portable Dehumidifiers For Small Wet Areas Excess moisture in small spaces can…
Reducing Mould Risk: Where To Place Water Damage Equipment Excess moisture is one of the…
The Best Equipment To Improve Indoor Air Quality After A Flood By: Brothers Equipment And…
What To Do When Sewage Backup Water Floods My Home By: Brothers Equipment & Supply…
