Air conditioning

Dry air vs. health

Dry air in heated rooms

In the wintertime, if cold outdoor air with its comparatively low absolute humidity is heated up by 10°C – 20°C (50°F – 68°F), the result is a considerable decline of the relative humidity because with rising temperatures the difference between absolute and maximum humidity increases considerably. This law of physics is one of the main reasons for low relative humidity that is often found in living and working spaces during the winter.

Many people don’t know this physical law and think that airing a room out frequently can increase the humidity in heated rooms. This idea is false because heating cold outdoor air inside buildings always leads to a considerable decrease of the relative humidity, although it may have been very high outside.

What does humidity cost if it is too low?

The Common Cold Foundation calculates that the yearly overall cost for cold-related illnesses comes to $5 billion for the US alone. Wage reduction, production loss and medical expenses make up the bulk of these costs. The health statistics of all industrialized countries reveal that cold-related illnesses are the most common illnesses and the main reason for loss of workdays.

The impact of low humidity on health

People used to believe that cold-related illnesses are primarily caused by breathing in cold air and the cooling down of the body. The discovery of pathogenic agents, like viruses and bacteria, changed this belief. The cooling down of the body is regarded as the reason for decreased resistance that creates a breeding ground for pathogenic agents. In recent times, opinions have changed as the cooling down of the body is not so much regarded as the main reason for a decreasing immune resistance, but rather because of dry air in heated rooms. Many ENT specialists support this opinion- because they see an increased number of patients with dryness of the mucous membrane in the upper respiratory tract during heating periods.

Dehydration of the respiratory system

The mucous membrane inside the nose, in the respiratory passages and the lungs with its alveoli constantly secretes mucus. Some parts of the mucous membrane have hairlike follicles, the so-called respiratory epithelium. When seen through a microscope, they seem to wave like a cornfield in the wind.

Our air humidifier and air purifier help against illness and allergies. The nose, throat and windpipe work like air conditioners by purifying, warming and humidifying the inhaled air. A large part of the dust that is inhaled is tossed against the mucous membrane by the centrifugal force and the vortex formation of the inhaled air. The movement of the respiratory epithelium transports the dust mixed with mucus to the nose. The nose and windpipe can be regarded as a filter system that cleans itself constantly. Strong blood circulation and continual moistening of the mucous membrane heat up the inhaled air to the body’s internal temperature and increase humidity close to the saturation point.

Inhaling air with low relative humidity over a longer period of time can cause symptoms of dry mucous membrane in the respiratory system. The first symptoms are an uncomfortable feeling of dryness in the nose and throat that can intensify to painful irritations. Mostly, speaking and swallowing are affected. The dryness also affects the cilia in their function, the mucus thickens and sticks to the mucous membrane. The whole self-cleaning system fails and bacteria are offered a favourable breeding ground. They can easily enter the dry mucous membrane and cause inflammations that occur with cold-related illnesses.

This is the theory behind the increased illnesses that occur during a heating period. Numerous doctors point out this correlation and suggest an increased level of humidity with a minimum of 40% in air humidity in schools, offices and flats during heating periods as a preventive measure.

Humidifying in the private spaces

Smaller steam humidifiers are mainly used for decentralized air humidifying in living and office spaces. Water is refilled by hand. The water reserve is enough for one day. The devices produce a hygienic clean humidity.