Best Available Techniques (BATs), defined in the Industrial Emissions Directive, are in essence the most effective techniques to achieve the prevention of environment and reduction of the emissions and environmental impacts while providing emission limit values and permit conditions.

It must be emphasized that BATs do not only refer to the technology used at an installation, but also to the way the installation is designed, built, operated, and maintained. Some BATs are a simple consequence of common sense and do not involve any investment.

In practice, to know if a given technique can be considered as a BAT, the following criteria must be considered:

-  If the technique is mentioned as a BAT in any of the BAT Reference Documents (BREFs), then it is a BAT.

- If it is not mentioned as a BAT in any of the BREFs, the technique should be evaluated taking into account the criteria listed in Annex III of the By-Law on Integrated Environmental Permits, to see whether it can be considered as a BAT or not. Those criteria are the following:

• The use of low-waste technologies;
• The use of less hazardous substances;
• The furthering of recovery and recycling of substances generated and used in the process and of waste, where appropriate;
• Comparable processes, facilities or methods of operation which have been tried with success on an industrial scale;
• Technological advances and changes in scientific knowledge and understanding;
• The nature, effects and volume of the emissions concerned;
• The commissioning dates for new or existing installations;
• The length of time needed to introduce the best available technique;
• The consumption and nature of raw materials (including water) used in the process and energy efficiency;
• The need to prevent or reduce to a minimum the overall impact of the emissions on the environment and the risks to it;
• The need to prevent accidents and to minimize the consequences for the environment;
• Information published by public international organizations.