Pay attention to reference values in performance ratings!

Contrary to the widespread assumption that “air performance is, after all, air conduction”, a very careful and differentiated approach must be taken when analyzing this important characteristic for an air filter device. The decisive factor is namely what the performance specification refers to exactly. Unfortunately, not all manufacturers of air filter systems speak the same language here; often the performance specifications confuse the non-expert.

To help you find your way through this data jungle, we have put together definitions of the three most important air flow rates for air filter units and air filter systems. It should be noted that all air flow rates are measured in cubic meters per hour – the technical reference is crucial. You should definitely check with the manufacturers of the air filter units that you wish to compare based on the air flow rates.

Extraction performance:
The extraction performance is the air volume that is available directly at the point where the contaminated air is extracted. For example, if an aerosol is to be extracted from a fully encapsulated machine tool via an extraction nozzle attached to the encapsulation, the extraction performance is the air volume that is available at this extraction nozzle when the control valve is fully open.

The suction power can, which may well be the case, be different for each suction nozzle in air filter systems in which several suction nozzles are combined via pipes or hoses. This is because the type of pipe or hose system and its length influence the suction power.

Air flow rate:
The air flow rate is the actual air volume that an air filter unit equipped with all accessories, such as hoods, extraction hoses, etc., can deliver. The air flow rate in the strict sense cannot be specified as a “catalog value” in the general technical data of an air filter system – after all, the accessories to be installed vary from application to application.

In order to still have a meaningful value, the air flow rate should be specified in the general technical data of the manufacturer of an air filter device as the “air flow rate of the device ready for operation, equipped with all filter elements, at its intake manifold”. The intake manifold should be the connection via which the polluted air enters the air filter device.

Fan performance:
The fan performance is the air performance that the fan of an air filter unit provides in a free-blowing manner. “Free-blowing” means that there are neither filter elements in the filter unit nor any accessories that would otherwise reduce the fan performance. In practice, this performance figure is irrelevant because these accessories are connected upstream in the subsequent use of the air filter unit.

The fan performance is always higher than the extraction performance or the air flow rate. However, it is only of importance to the designer of an air cleaner. In practice, air cleaners should not be compared on the basis of the fan performance – the extraction performance or the air flow rate must be the decisive factor for a comparison.