What is a mere duct in the air conditioning system

When death comes from the air conditioning

The harmful effects of poorly maintained air conditioning systems have been known since 1976 at the latest. At that time there was a meeting of veterans of the American Legion in a hotel.

Those responsible can prevent this through regular, professional cleaning of the water systems and the supply and exhaust air ducts. Since January 1, 2003, the new Drinking Water Ordinance has made it mandatory for operators of public facilities to test for Legionella.

The harmful effects of poorly maintained air conditioning systems have been known since 1976 at the latest. At this time a meeting of veterans of the "American Legion" took place in a hotel in Philadelphia / USA. 221 participants developed severe pneumonia and 34 died. The cause: bacteria that had settled in the ventilation ducts of the air conditioning system.

In 1977 researchers at the Center for Disease Control (CDC) in Atlanta / USA succeeded in discovering the rod-shaped pathogens that triggered this first epidemic and were therefore christened “Legionella”. So far 44 different species are known, the best known is the "Legionella pneumophila". The disease it causes is called "Legionnaires' disease" (also called "Legionellosis" or "Legionella pneumonia"), and the less dangerous Pontiac fever can also occur (see box).

Rapidly spreads in warm water

Legionella cannot be seen with the naked eye. Only by means of strong magnification under the microscope can the very small, about 0.3 to 2 thousandths of a millimeter large living beings be made visible at all. They live mainly in water, i.e. in rivers and lakes, but also in artificial systems such as water pipes or sewage systems. They reproduce at temperatures between 25 and 50 ° C, but they can also survive heat up to 63 ° C. Under ideal microbiological conditions, they double their population through cell division within three to four hours, which means that Legionella can multiply 4000-fold within just two days.

"Legionella thrive particularly well in heated water and thus, for example, in cooling

and air conditioning systems, whirlpools, swimming pools or cooling towers ”, knows the trained heating and ventilation master builder Andreas Schindhelm from the industrial and commercial service Schindhelm & Sohn in Kinding, Bavaria. Its task is the professional cleaning of supply and exhaust air systems in swimming pools and hospitals, laundries, offices, department stores, restaurants and other large companies.

Infections result from inhaling the smallest water droplets (aerosols) containing Legionella, such as those caused by showering, certain humidifiers or poorly maintained air conditioning systems. "That is why it is extremely important to regularly clean and check the water and ventilation systems," advises Schindhelm. His employees mainly carry out orders at night so as not to disrupt the customers' business operations. They come with a water hose, high-pressure cleaner, spatula, cleaning agents and disinfectants. They also bring a low-voltage transformer with them, which provides light in the sewer lines when they go into the sewer to remove the dirt. "A superficial cleaning of the systems is of no use, you really have to go into the sewer," says Schindhelm. "Recently, cleaning robots, which have also been tested by our company, have been used, but these machines do not clean as well as the employee who mechanically removes the dirt."

Microbiological and chemical studies

The new Drinking Water Ordinance has been in effect since January 1, 2003, which, in connection with the Infection Protection Act, requires operators of water supply systems to conduct regular inspections and clearly regulates the issue of liability in the event of infections. "Then even those who previously thought that Legionella was not an issue for them will have to rethink," says Schindhelm. Since January 1, 2003, “entrepreneurs and other owners of a water supply system”, as the ordinance states, have had to regularly carry out or arrange for microbiological and chemical tests.

The results of this monitoring must be recorded and reported to the health department if certain parameters are exceeded. This is especially true if Legionella is found in the water. From this point in time at the latest, the law of action rests with the authority, which can order all measures that are necessary to protect health - up to and including the closure of the company. Operators of water supply systems who violate these regulations are guilty of an administrative offense or even a criminal offense. In order to keep the risk of such health hazards as low as possible, several ordinances such as the VDI standard 6022 have for a long time stipulated the regular inspection and cleaning of air conditioning and ventilation systems as per standard. However, up to now, many entrepreneurs were unaware of their obligations and the dangers of uncleaned or insufficiently cleaned exhaust and supply air systems. "It is estimated that 80 percent of all ventilation ducts have not been cleaned for years," fears Andreas Schindhelm. For a well-functioning and germ-free system, regular thorough cleaning and, if desired, subsequent disinfection and, above all, a good condition of the filters is important. “These have to be replaced and checked regularly. But this is by no means a task for the staff, but only for the specialist. A professional approach as well as suitable protective clothing and dust masks are absolutely necessary in order not to endanger health. ”A normal filter contains as much dust and dirt as a human lung removes in 80 years.

Every year around 6000 diseases in Germany

According to estimates by the Robert Koch Institute in Berlin, around 6,000 people in Germany fall ill with Legionnaires' disease every year. However, only a fraction of this is officially registered. The outbreak of legionnaires in the Spanish city of Murcia made headlines in July 2001. The disease was clearly diagnosed in over 300 patients, the number of suspected cases rose to over 700. One death could be safely attributed to Legionnaires’s disease, in another the connection was not officially confirmed. The condition of 12 patients in the intensive care unit was critical, according to the Spanish Ministry of Health. During investigations in Murcia, Legionella was found in 14 air conditioning systems, including a large department store and administrative and government buildings. In Germany, Legionella was detected in a swimming pool in Meerbusch in July 2002, and a swimming pool in Kusterdingen (Tübingen district) was affected in October 2002.