Carpet, mould and Hong Kong's humidity
Why carpets go musty in Hong Kong, how to tell when mould is a problem, how to keep humidity down in spring, and when a carpet can't be saved.
Anyone who's lived through a Hong Kong spring knows the feeling. Walls sweat, floors turn slick, and clothes never quite dry. Carpets go through it too.
How damp does it get?
According to the Hong Kong Observatory's 1991–2020 climate normals, mean relative humidity is:
| Period | Mean relative humidity |
|---|---|
| Annual average | 78% |
| March | 82% |
| April and May (highest) | 83% |
| June | 82% |
| December (lowest) | 70% |
Those are averages, so on bad days, it can be far higher. Guidance such as Cigna Hong Kong's on dust mites recommends keeping indoor humidity at 50% or lower. Getting anywhere near that in Hong Kong takes active effort.
Why carpets are vulnerable
Mould needs moisture, warmth and something to feed on. Carpet can offer all three. Dust and skin flakes provide food, and thick pile, underlay and backing can hold moisture out of sight. Rugs on stone or tile floors can trap condensation underneath.
How to tell if you have a problem
- A musty smell that returns soon after vacuuming
- Dark or discoloured patches, often near walls, windows or under furniture
- A damp feel in the carpet or backing
- Spots on the back of a rug when you lift it
- Allergy-like symptoms that seem worse in that room
Check underneath furniture that hasn't been moved in months, and lift rug corners to look at the back and the floor beneath.
Prevention
Control indoor humidity. A dehumidifier or air-conditioning is the most effective tool you have. An inexpensive hygrometer tells you how you're actually doing.
Know when to close the windows. On humid days, especially during the spring "back to the south" weather (回南天), opening a window can let in air that's wetter than what's indoors.
Keep air moving. Fans help reduce still, damp pockets, so leave some space around heavy furniture.
Vacuum regularly. Removing dust takes away what mould feeds on.
Deal with spills and leaks immediately. Soak up what you can, and dry the area fast. As a general rule, aim to dry wet materials within 24–48 hours.
Check before going away. Closed-up flats get damp quickly. A dehumidifier with a drain hose can help, if it's safe to leave running.
Store rugs properly. Clean and dry them first, wrap them in something breathable, not plastic, and keep them off the ground if you can.
What to do if you find mould
- Find the source. A leak, condensation, or a damp wall will bring the problem back unless it's fixed.
- Dry the area thoroughly.
- Assess the scale. Small, new spots on a washable surface are one thing. A carpet that's been wet for a long time is another.
- Protect yourself. Avoid dry-brushing mould into the air. Anyone with asthma, allergies or a weak immune system should stay out of it.
- Get advice. Send us photos. If the carpet's only surface-affected, a deep clean may help once the source is fixed.
When a carpet can't be saved
If it's been soaked for days, especially by dirty water, or mould has spread through the underlay, replacement is usually the safer choice. Cleaning can't guarantee a carpet is free of mould, and we won't tell you otherwise. Serious water damage needs a water damage specialist.
Can a professional clean make things worse?
Yes, if it's done carelessly and the carpet stays wet. That's why we treat drying as part of the job and plan it around your space. If you're in the middle of a humid spell and it isn't urgent, it may be worth waiting for a drier week. How often should you clean your carpet covers the best time of year to do it.
