Hong Kong's humidity is high, whether in new or old buildings, black spots may appear in corners, wardrobes, and even air conditioning vents. Many tenants think wiping them away is enough, but mold is actually a health warning—long-term inhalation of mold spores can cause respiratory and skin allergies, and even trigger asthma. Today, we'll break down why homes get moldy, how to deal with it immediately, and how to prevent it in daily life.

Q1｜Why is the home damp and moldy?

Three most common reasons:1️⃣ High humidity: Hong Kong's average annual humidity is 70%–90%, combined with sealed windows that trap moisture.2️⃣ Condensation from temperature changes: Air conditioner vents, glass windows, and bathroom ceilings are prone to condensation, leading to mold spots.3️⃣ Poor ventilation: Long-term window closure, lack of exhaust fans, and wardrobes placed against walls cause moisture buildup, especially on north-facing walls or in bathrooms.

💧 Tip: When humidity exceeds 60%, it's the "golden growth period" for mold, so address it promptly.

Q2 | How do dampness and mold affect health?

• Short-term reactions: Stuffy nose, sneezing, itchy throat, skin itching.
• Long-term effects: Mold spores can worsen asthma, allergic rhinitis, and chronic rhinitis; people with low immunity or children are particularly susceptible.
• Common household locations: Corners of bathrooms, window sills, back panels of wardrobes, air conditioner vents, spaces under beds.

Q3｜How to deal with a humid home?

💪 Do It Yourself (DIY Methods)

1️⃣ Keep the exhaust fan running and ventilate daily by opening windows: Maintain air circulation. 2️⃣ Turn on the dehumidifier or air conditioner in dry mode: Keep humidity at 45–55% for the best results. 3️⃣ Slight mold on walls — Use a dry cloth with alcohol: First wipe away the mold with a dry cloth; if not removed, gently wipe with a small amount of 70% alcohol. 4️⃣ More severe mold — Remove with sandpaper: If mold spots penetrate the wall, lightly sand the surface with fine sandpaper, then wipe dry. 5️⃣ Deep cleaning — Spray professional mold root removal products: After cleaning the surface, spray on the mold root remover and wipe with a dry cloth to penetrate the wall and remove mold roots. It is recommended to re-spray 1–2 times a year to prevent mold regrowth. 6️⃣ Prevent regrowth — Use anti-mold wall paint: If planning to repaint, choose "anti-mold wall paint" or "moisture-resistant primer" for longer-lasting protection. 7️⃣ Clothing mold prevention: Place desiccants or moisture-absorbing packs inside the wardrobe; if the wardrobe is kept closed for long periods, open the door regularly for ventilation. 8️⃣ Move furniture away: Keep the back of cabinets 3–5 cm away from the wall to avoid direct contact.

💼 Professional Services

1️⃣ Anti-mold Coating/Nano Coating: Can inhibit mold regrowth, suitable for corners or ceiling areas. 2️⃣ Infrared Leakage Detection: Professional companies can identify the source of leaks/condensation. 3️⃣ Structural Moisture-proof Engineering: If it's due to external wall leakage or underground moisture seepage, the owner needs to hire a contractor for repairs.
Hong Kong's weather is humid, and mold grows quickly. Remember not to delay when you see black spots - the earlier you address it, the less likely it will become a health problem.