If you're a Singapore HDB homeowner, you've likely encountered this frustrating problem: despite keeping your bomb shelter door closed, mould keeps appearing on walls, belongings, and even that expensive leather bag you stored "safely." Let's explore why this happens and what you can do about it.
Why Bomb Shelters Are Mould Hotspots
HDB Household Shelters (commonly called bomb shelters) are particularly vulnerable to mould due to their design:
1. Enclosed Concrete Construction
Bomb shelters are built with thick reinforced concrete walls for protection purposes. Unfortunately, concrete absorbs moisture from the surrounding air and can release it slowly, keeping the interior perpetually damp.
2. No Ventilation
Unlike other rooms, bomb shelters typically have:
- No windows
- A sealed door (by design)
- Limited to no air circulation
This means moisture that enters has no way to escape.
3. Temperature Differences
The concrete walls stay cooler than the ambient air, especially when you run the AC in adjacent rooms. When warm, humid air meets these cold surfaces, condensation forms – the same principle as water droplets on a cold drink.
4. Common Usage Patterns
Most homeowners use bomb shelters as storage, filling them with boxes, clothes, and items that:
- Reduce air circulation further
- Provide organic material for mould to feed on
- Trap moisture in hidden areas
Prevention Strategies That Work
1. Use a Dehumidifier
This is the most effective solution. A small dehumidifier (10-20L capacity) running continuously can maintain humidity below 60%:
- Choose one with a continuous drainage option
- Set it to maintain 50-55% humidity
- Expect to run it 24/7 during monsoon season
2. Improve Air Circulation
Even in a sealed space, you can improve air movement:
- Leave the door slightly ajar when possible
- Use a small fan to circulate air
- Don't pack items too tightly – leave space between boxes
3. Moisture Absorbers
For additional protection:
- Place calcium chloride moisture absorbers in corners
- Use silica gel packets among stored items
- Replace when full (check weekly in humid months)
4. Treat Surfaces
Prevent mould from establishing on walls:
- Apply anti-mould paint on concrete walls
- Use antimicrobial spray treatments
- Seal concrete with moisture-resistant coating
Smart Storage Practices
What and how you store matters:
- Avoid storing: Leather, fabric, paper, and organic materials without protection
- Use plastic containers: Airtight bins protect contents from ambient humidity
- Elevate items: Use shelving rather than placing things directly on concrete floor
- Check regularly: Inspect stored items monthly for early mould signs
Frequently Asked Questions
Why is my bomb shelter always damp even with the door closed?
Bomb shelters are designed as enclosed concrete spaces, which naturally collect moisture from the surrounding air. The thick concrete walls absorb and release humidity, and without ventilation, moisture has no escape route. This creates a perfect environment for mould growth.
Can I use silica gel packets to prevent mould in my wardrobe?
Yes, silica gel and moisture absorbers can help in small enclosed spaces like wardrobes. However, they need regular replacement (every 2-4 weeks in Singapore's humidity). For bomb shelters, you'll need larger dehumidifiers as silica gel alone won't be sufficient for the space.
How often should I clean my shoe cabinet to prevent mould?
Clean your shoe cabinet at least monthly with an anti-mould solution. Wipe down shelves, allow shoes to dry before storing, and use moisture absorbers. In humid months, increase cleaning frequency to every 2 weeks.
Is it safe to use my mouldy bomb shelter for storage?
It's not recommended to store items in a mouldy bomb shelter as mould can damage belongings and release spores into your home. First, address the mould problem and implement humidity control before using the space for storage.
Why do my leather items get mouldy faster than other materials?
Leather is an organic material that absorbs moisture easily and provides nutrients for mould. In Singapore's humidity, leather items need extra protection: store with silica gel, allow air circulation, and clean regularly with leather conditioner that has anti-mould properties.