6.1.1 Introduction

In process technology and in the manufacture of equipment and systems, the starting point of design includes very precise targets. For example, in car man­ufacture target levels for main characteristics of the car (e. g., acceleration, maximum speed, and gasoline consumption) are already set in the drawing ta­ble. In this case the target values of engineering are also the characteristics to be validated when the product is ready.

Target levels (TLs) refer to the expected values of the system that are de­termined at the early stages of the design process. Fulfillment of the target lev­els should be validated or measured by the individuals or organizations responsible at the end of the construction process. Target levels are needed as a standard against which system solutions are compared. During the compari­son it may be found that target values cannot be met by any solution or they can lead to very expensive solutions. In such cases the target levels have to be reconsidered. The target level assessment is a feedback process, as explained in Chapter 3.

Target levels can be utilized at many levels and areas of technology. Some examples from industrial air technology follow:

• Energy efficiency given as a percentage

• Energy usage per cubic meter or square meter of a building, such as for the heat consumption in buildings

• Energy usage per produced unit of final product(s), for example, energy use for each produced ton of stainless steel

• Indoor air quality

• Reliability, for example, how many breaks are accepted per day

• Emission rate

• Capture efficiency of the local exhaust

• Investment cost and maintenance cost

• Expected lifetime of a plant and its components

• Ecological issues

Because the goal of industrial air technology, as defined in Chapter 1, is to control indoor environmental conditions and emissions, special attention must be paid to the indoor conditions and contaminant content of the ex­haust air. The need to define target levels for indoor conditions and exhaust air blown outdoors originates from legal requirements, human health re­quirements, production processes and equipment, and is also related to the type of premises and construction. Target levels should be defined for ventila­tion systems as well as many other items in the construction process. Target levels should always be dealt simultaneously with design methodology. A de­cision tree for the target level steps and design methodology is provided in Chapter 3.