12.3.1 Introduction

In the wide field of industrial ventilation many factors require measurements to be carried out. One of the most common is the commissioning of a new or a renovated ventilation system. In this case the client has to see that the system works according to the specifications made with the consulting engineer, man­ufacturer, and contractor. Many other situations require quantitative informa­tion on ventilation and related systems, like

The satisfactory functioning of a ventilation system,

Troubleshooting in existing facilities,

Testing the dynamics of subsystems, such as controls,

Determining reasons for complaints,

Checking on specified target values in a space,

Carrying out an energy audit,

Collecting data for renovation planning, and Collecting boundary values for a computational approach.

The only method to determine the actual system performance is to carry out measurements. The questions to be answered are: What should be measured? How and when? How should the results be interpreted? Some of the answers to these questions are found in the following sections.

The most common quantities to be measured in the field of industrial ventilation are air temperature, humidity, airflow rate, velocity, pressure

Difference, and the concentration of different contaminants. Besides these, some other quantities, such as temperatures of other media (water, solid surfaces), noise and vibration, some additional air quality parameters, and tracer concentrations may be required. From these many other quantities can be calculated, like energy use, the thermal environment, air quality, or ventilation efficiency.

On-site measurement is not the only approach to gain information on a system. In the case of a building/system at the planning stage, it is not possible. Measuring is also expensive, especially if carried out on a large scale for a long time. If quantitative information (numbers) is not absolutely necessary and qualitative information (visual observation, video, photographs, etc.} will do, visualization is an alternative in investigating flow patterns. Visualization can also be used to supplement the measurements or vice versa. If, however, num­bers are required, reduced-scale measurements can be used. They can be car­ried out also during the planning stage by constructing a scale model. Finally, modelling techniques like CFD or thermal/zone models can be used in some cases as an alternative for measurements.

Careful consideration has to be given to all aspects of each approach—such as the reliability, the total cost, and the need for equipment and expertise—before making the final decision. The main advantage of measurements is the reliability of the results, the disadvantage being the need for often expensive equipment.