What humidity setting on a dehumidifier stops house dust mites and mould?

Humidity target: 40%–50% is a fairly safe range

House dust mites like damp, and mould also grows on moisture. Keeping indoor relative humidity at 40%–50% can both suppress house dust mite breeding and make it harder for mould to grow. Below 40% feels dry, and above 50% the risk goes back up.

This range is not a hard standard, but it can be used as a reference for everyday adjustment. When using a dehumidifier, you can set it to around 45% and let it start and stop automatically; there is no need to aim for the lowest possible level.

If you have a hygrometer at home, you can watch it for a few days to find the setting that suits your home. If you do not have one, the humidity display on the dehumidifier can also be used as a reference.

The rainy season in the south and the heating season in the north need different focus

During the rainy season in the south, air humidity often exceeds 70%, and the dehumidifier needs to run for long periods. You can close doors and windows and keep humidity below 50%, while also paying attention to blind spots such as wardrobes and wall corners.

During the heating season in the north, it is dry outdoors, but indoors it may be locally damp because of drying clothes, cooking or showering. At this time you do not need to run it all day; focus on the bathroom, kitchen and clothes-drying area to keep moisture from spreading.

In winter, the temperature difference between indoors and outdoors is large, and condensation easily forms near windows. You can open windows briefly for ventilation and combine this with dehumidification to reduce the mould risk caused by condensation water.

How to balance dehumidification and comfort? Do not make the room too dry

If humidity is too low, people may have a dry mouth, tight skin, and the airways may also feel uncomfortable. If you feel dry, you can set the target humidity a little higher, or put a basin of water in the room to evaporate naturally.

A dehumidifier makes wind noise and slight warming when running; place it in the living room or hallway, and avoid blowing it directly at the head of the bed. If it feels noisy when sleeping, you can lower the fan speed or set a timer to turn it off.

If there are older people, children or people with sensitive skin at home, pay more attention to how they feel. Humidity is not better the lower it is; it is best when people do not feel stuffy or dry.

Where to put the hygrometer and how to read it so it reflects the real situation

Do not put the hygrometer in a wall corner, by the window or at the door; these places are strongly affected by the outdoors. Put it in the centre of the room, at a height of about one metre above the floor, away from air-conditioner vents and direct sunlight.

If you have only one dehumidifier, you can put it in the area with the highest humidity, such as the basement or a north-facing room. Use the hygrometer to compare different rooms and find the places that need dehumidification most.

Mould likes damp corners, such as behind wardrobes, under mattresses and in bathroom corners. You can check these places regularly and, if necessary, dehumidify locally or ventilate.

When should you see a doctor?

If, after adjusting humidity, nasal congestion, runny nose, cough or wheezing still recur and affect sleep or daily activities, it is advisable to see a doctor for assessment.

If a rash does not heal and keeps coming back, the skin is broken and oozing, or the eyes are red, swollen and unbearably itchy, it is also worth having a doctor look at it.

If a child has hearing loss, persistent ear fullness, or repeated sinus infections, allergy and other factors need to be checked.

If a person with asthma has worsening symptoms or uses reliever medicine more often, they should see a doctor promptly and should not rely on environmental control alone.

This article is for general information only and is not medical advice. Please follow your doctor's instructions for specific matters.