Laws and Regulations
26. February 2019

42nd BImSchV - Federal Immission Control Act

42nd BImSchV - Ordinance on evaporative cooling systems, cooling towers and wet separators

42nd BImSchV – Hygienic operation of evaporative cooling systems

The Ordinance on Evaporative Cooling Systems, Cooling Towers and Wet Separators (42nd BImSchV) came into force on August 19, 2017 in accordance with Section 20. This is based on the VDI cooling tower rules (VDI 2047 Sheet 2) and makes them binding. In addition, there are recommendations for the installation and operation of evaporative cooling systems, cooling towers and wet separators.

The aim of the 42nd BImSchV is to use state-of-the-art technology to prevent contamination of the cooling system with legionella and thus minimize the health risk for the population. The regulation also provides for better control of evaporative cooling systems, cooling towers and wet scrubbers. Contamination of the cooling tower with legionella should be prevented by strict operator obligations.

The most important points for operators of evaporative cooling systems, cooling towers and wet scrubbers are summarized below.


Obligations of operators of evaporative cooling systems

According to §4 (2), operators of evaporative cooling systems, cooling towers and wet separators must ensure that, in order to ensure the hygienic quality of the process water, regular internal checks of chemical, physical or microbiological parameters are carried out every two weeks.


Cooling water quality monitoring – sampling

Water samples must be examined regularly to monitor the cooling water quality. External laboratory tests on the general colony count and specifically on the Legionella parameter must still be carried out at least every three months. Samples must be taken by a trained sampler and analyzed by an accredited laboratory.

An initial inspection is required as early as 4 weeks after (re)commissioning the cooling system, and regular inspections of evaporative cooling systems are required every three months. The investigations are to be documented in the operations log.


Obligation to inform in case of exceeding

If a laboratory test determines that the measure values ​​have been exceeded, the operator must inform the responsible authorities immediately. The results of the expert review must be reported within four weeks.


operations diary

The operator must keep an operating log to check that the system is operating properly. This must be presented to the competent authority as well as to experts within the scope of the review at any time upon request.

The operations log includes microbiological findings and operational data of the cooling system. In addition to the reference value of the general colony count, this includes exceeding the test and action values, measures taken to restore cooling water hygiene, as well as changes in the cooling system and the addition of biocides.


Compulsory notification from August 2018 / KAVKA

According to §13, there is a notification obligation for new and existing systems, so the operator of an existing system must notify the responsible authority of his system no later than one month after July 19, 2018. New systems must be reported after they have been filled. Changes to the cooling system, a decommissioning of the cooling system and a change of operator must also be reported.

With the introduction of the notification obligation for new and existing facilities, the local authorities can act faster and more effectively in the event of a legionella outbreak and identify possible venues. The aim is to create a register that links all evaporative cooling systems to one location and one person responsible for the system.

In order to report an installation, operators must first register in the cadastre KAVKA-42BV on the following website:

Here you enter your first and last name, e-mail address and a password. After successful registration, the e-mail address must be verified, for this you will receive a confirmation e-mail. Please note: the verification link expires after 120 minutes.

Further information on registration can be found in the following PDF: 
After successful registration, you can log into the KAVKA portal and enter the system data. 
First the operator data and then the workplace must be recorded.


The system itself requires the following data:

  • plant designation
  • Facility ID – The facility ID consists of the 42BV identifier of the workplace (is automatically specified) and a freely selectable 4-digit facility number. (e.g. 0001).
  • Investment Type - Choice of 3 investment types
  • Coordinates - selection option via map display
  • longitude
  • latitude
  • System built on XXX - selection option via calendar
  • System put into operation on XXX - selection option via calendar
  • Status - is set by the system from the date "Plant built on" and the date "Plant put into operation on"

More information on the required data can be found in the following PDF:


Determination of the cooling tower-specific reference value

After the commissioning or recommissioning of an evaporative cooling system, the reference value of the service water (cooling water) must be determined from at least six consecutive laboratory tests for the parameter general colony count.

The reference value reflects the microbial contamination in the service water that is typical for the system during proper operation. With the help of this microbiological normal state, deviations can be recognized as an indicator of hygienic changes in the systems.

If the laboratory test found an increase in the concentration of the general colony count by a factor of 100 or more compared to the reference value, the operator must immediately carry out investigations to clarify the causes and take the necessary measures to reduce the microbial load in order to ensure proper operation .


expert supervision

After commissioning and every five years, the operator must commission an expert to check that the system is operating properly. For existing systems, a staggered inspection of the systems is required.


Test- ​​and action values ​​for the concentration of legionella in process water

Legionella concentration [Legionella spp.] in the cooling water of evaporative cooling systems

42nd BImSchV
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