Hygrometers, which measure indoor humidity, can be bought at many hardware stores.

Humidifiers and dehumidifiers help to keep indoor humidity at a comfortable level.

Remember that reducing indoor humidity is important if condensation is a problem.

Do all you can to lower indoor humidity.

Lower indoor humidity causes each breath to evaporate a greater amount of water.

Minimize the number of house plants, and do what you can to lower indoor humidity (air-conditioning helps a lot in warm weather).

And when the indoor humidity drops below 20 percent for three days, the index warns, everyone is at risk of severe symptoms.

Reduce indoor humidity to less than 50 percent.

Keep indoor humidity below 55% and use vents in bathrooms.

However, even with these precautions, changes in weather can affect indoor humidity.