Humidity is the amount of water present in the air. Indoor humidity is important for health. Unbalanced humidity can cause health consequences. The eyes get dry and irritated, the skin is flaky and itchy, the low humidity inflames and the mucous membrane covering the respiratory tract dries out. As a result, there is a considerably increased risk of cold, flu, and other infections. Ideal indoor humidity should be between 40% and 60%.

Another serious effect of the decrease in indoor humidity is on the respiratory and immune systems. Mucous membranes in our nose, throat, and bronchi are a defence against airborne pollutants such as viruses and bacteria. But due to decrease in indoor humidity, the air turns dry, which dries out the mucous, membranes in our throat, nose and bronchi. So the body’s natural mechanism to block the harmful virus particles is destroyed and we are more susceptible to respiratory viruses. Also, lower humidity causes transmission and survival of airborne viruses longer in the air, so we have a great chance of developing respiratory illnesses such as cold and flu.

Another reason for the decrease in indoor humidity that increases the risk of respiratory illnesses is the emissions from indoor sources like building materials, furnishings, office equipment, outdoor factors such as pollen and particulate matter which lead to accumulation of dust, chemical and biological compounds that enter in our respiratory system and damage it. Many viruses survive at low humidity for longer, further helping to increase your chances of getting sick. Dry conditions can also cause “infective aerosol” droplets to quickly lose their mass via vaporization. In other words, the droplets dry out after someone sneezes but the viruses linger, able to float in the air forever – eventually making their way into the dry respiratory tract. 

It is important to manage the indoor humidity to prevent dryness and irritation symptoms at workplaces, homes, and schools. Indoor air humidity can be improved with:

• Interventions at the central or building level that raise air humidity with air conditioning systems or whole-house humidifiers
• Local or spatial measures, such as separate air humidifiers which can be triggered on request.
• Use a humidifier or vaporizer
• Boil water on your stove.
• Place bowls of water in various locations in your home.
• Take a shower and create a steam bath.

Indoor humidity level and quality play an important role in the well-being of a person. So maintaining the 40%-60%RH is an effective way to reduce the risk of airborne infection and respiratory illnesses.