Air Quality
Dehumidifiers: Sizing, Mould Control and Running Costs
For a large part of India, humidity is a bigger indoor problem than dust. Mumbai, Chennai, Kochi, Kolkata, Goa and the whole coastal belt spend months above 75% relative humidity, and the consequences are familiar: a musty smell that never quite leaves, black spotting on bathroom ceilings and wardrobe backs, leather and camera gear growing fungus, clothes drying in three days, and condensation on cold surfaces.
None of that is an air-purification problem, and an air purifier will not touch it. It is a moisture problem, and the appliance for it is a dehumidifier.
It is also worth knowing that reducing humidity below 60% is one of the more effective things you can do for dust-mite allergy, because mites cannot maintain their water balance in drier air.
Compressor or desiccant?
| Compressor (refrigerant) | Desiccant | |
|---|---|---|
| How it works | Cools a coil so moisture condenses out | Adsorbs moisture onto a rotating desiccant wheel, then drives it off with heat |
| Best temperature range | Above ~18°C — most of India, most of the year | Below ~15°C, where compressor coils frost |
| Efficiency in Indian conditions | Better | Worse — uses more power for the same extraction |
| Air temperature effect | Slight cooling | Warms the room by 1–3°C |
| Noise | Compressor hum | Generally quieter |
| Verdict for India | The default choice | Niche — hill stations, cold storerooms |
Sizing — the number that matters is litres per day
Dehumidifier capacity is quoted in litres of water extracted per 24 hours, usually measured at a flattering 30°C and 80% RH. Real extraction in your conditions will be lower, so treat the headline figure as a ceiling.
| Situation | Suggested capacity | Notes |
|---|---|---|
| One bedroom, moderate damp | 10–12 L/day | Adequate for 100–150 sq ft |
| 2BHK flat, coastal monsoon | 20–25 L/day | Move it between rooms, or buy two |
| Whole flat, persistent damp | 25–50 L/day | Consider continuous drainage to a floor drain |
| Basement or storeroom | 25–50 L/day | Also check for water ingress — a dehumidifier treats symptoms, not a leak |
| Server room / archive | Specified by RH target | Needs a humidistat and continuous drain |
Tip
Using one properly
- Close the room. A dehumidifier fighting an open window is running against the entire outdoor atmosphere.
- Set a humidistat target of 45–55% and let it cycle, rather than running continuously at maximum.
- Keep it away from walls and furniture so air can circulate through it freely.
- Do not use one to fix a leak or rising damp. If a wall is wet from a source, the appliance only masks it — find and fix the source.
- In monsoon, run it in the room where laundry dries. It will dry clothes faster than a fan and stop that moisture loading the rest of the flat.
- Clean the intake filter monthly, and the coils occasionally. A clogged filter cuts extraction sharply.
Mould — what a dehumidifier does and does not do
Mould needs moisture. Holding indoor RH below about 60% removes the condition mould needs to establish, which is why a dehumidifier is the correct primary tool for a musty flat.
It does not remove mould that has already grown. Existing growth needs physical cleaning of the affected surface, and if it covers a large area or keeps returning, the underlying water source needs fixing. An air purifier will capture airborne spores, which helps with symptoms, but it does not address the cause either.
Prices and options
| Budget | Capacity | Suits |
|---|---|---|
| ₹8,000 – ₹15,000 | 10–12 L/day | One bedroom, moderate damp |
| ₹15,000 – ₹25,000 | 20–25 L/day | 2BHK in a coastal city — the common sweet spot |
| ₹25,000 – ₹45,000 | 25–50 L/day, continuous drain | Whole flat, basements, persistent damp |
| ₹45,000+ | Commercial / industrial | Warehouses, archives, production areas |
Indicative Indian market ranges for budgeting, not quotations. Prices move frequently — always confirm on the marketplace or with a supplier before purchasing.
Where to buy
We have not individually tested products in this category, so we are not going to rank them as though we had. Use the buying criteria above to judge listings yourself, and these searches as a starting point.
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