• a desire to implement the optimal conditions for the growth of microbiological objects requires the use of high level of toxic components, which in real terms would lead to excessive effect “overkills”;
• Exposure usually limited to a relatively small number of different types of microorganisms;
• Exposure is limited by temperature and time;
• incorrect interpretation of the data obtained by non-experts in this field.

It is also important to understand that some chemicals can be very toxic to microorganisms in the short-term accelerated tests, lasting 14-21 days, but their effectiveness may decline with long-term exposures. For example, fungicides may simply boil down to the hot atmosphere to collapse under the action of ultraviolet radiation, or washed out by rain or dew.

Full-scale tests to investigate the durability of PEX materials to bacteria and fungus and their limitations

The tests in the open air, conducted to evaluate the durability of PEX materials to the action of microorganisms, performed on a variety of techniques. The simplest test consists in the fact that the samples are simply placed in the open space in the geographical area that is most favorable for the growth of microbiological objects.

An alternative way of testing is called the method of burial in the soil. This method consists in the fact that the samples buried in the ground for four weeks, and then studied the results of the influence of microorganisms on the samples.

The need for assessments of the effectiveness of various antimicrobial additives as at laboratory level and in real-life conditions in the open air led to the development of many different test methods. These methods and limitations associated with their use, as will be discussed in this chapter.