What are Mold & Mildew?
Mold & Mildew are a type of fungus that grows on many different types of surfaces where the right conditions of moisture and temperature exist. The spores that cause mold & mildew are ever present in the air but can only cause problems when the surface is damp which in bathrooms is usually caused by condensation.
What causes condensation?
Condensation is caused where humid air meets a cooler surface. The air around us holds moisture and the warmer the air is, the more moisture it can hold. So, the warm air is cooled when it meets a cooler surface and it can no longer hold the same amount of moisture and releases it as condensation. The warm moist air in a bathroom when the bath or shower is used results in very high amounts of moisture in the warm air and results in high amounts of condensation.
How to get rid of condensation - reduce the humidity...
High levels of humidity caused by baths and showers must be reduced quickly to prevent the mildew from growing. Ventilation is the quickest way of reducing the humidity, so turn the bathroom fan on that's the reason it is there, if you haven't got one, install one. There must be sufficient area under the door or from the window to let dryer air to replace the damp air extracted. Heating increases the amount of moisture that can be held in the air. In other rooms the principle is the same, kitchens should have a fan as close to the steam source as is practical and in bedroom ventilation and some heating is essential.
How and when to ventilate?
In general it is best to ventilate little and often, many windows open slightly is better than one open fully. Continuous trickle ventilation will reduce humid air causing damage in most rooms. However, in bathrooms and kitchens the sudden bursts of humidity when using the bath, shower or the cooker respectively, will require more vigorous ventilation at these times. There are fans that supply both trickle and boost ventilation triggered by either the humidity, PIR (Passive Infra Red) sensors or activated by the light switch.