A study coordinated by the Finnish Institute of Occupational Health (FIOH) detected deficiencies in the performance of air filtering equipment connected to machine tools used in machining shops.

The study says the problem is related to metalworking fluids that release mist and various gaseous pollutants into the air during work, exposing workers to the risk of skin and respiratory symptoms.

The problem is related to metalworking fluids that release mist and various gaseous pollutants. Credit: FIOHIn the study, a method was developed to enable the control of gaseous air pollutants. Other means to reduce the release of pollutants into workspace air were also investigated.

Exposure to air pollutants generated by metalworking fluids affects machinists in particular, but other machine and metal professionals working in machining shops may also be exposed. Metalworking fluids used during machining with chip removal, such as turning, milling, drilling, cutting, shaving or grinding, form aerosol containing both particulate and gaseous compounds harmful to health.

This study, coordinated by FIOH, detected deficiencies in local exhaust ventilation air filtering generally used in the machining centers of machining shops. The filtering equipment generally used in machining centers is not capable of removing gaseous pollutants generated by metalworking fluid. Even though individual pollutants do not reach concentrations known to be harmful, workers exhibit symptoms, such as rhinitis, coughing, ocular symptoms, shortness of breath, asthma, and other respiratory symptoms.

The pollutants detected in workspace air were mainly alkanolamines and volatile organic compounds (VOC). From the measured concentrations of alkanolamines, 77% exceeded FIOH’s recommended target level of 0.1 mg/m³. The HEPA filters commonly used in air filtration units retain particulate pollutants but the pollutants found in the vapour phase, such as alkanolamines and volatile organic compounds, penetrate the filters.

On the basis of the study, FIOH says that one of the following measures is needed at workplaces:

1. The air from the filtering equipment of the machining centers should be led directly outdoors from the workspace. From the perspective of energy efficiency however, this is not necessarily the best solution.

2. The ventilation of the workspace should be significantly increased, with the aim of diluting the air pollutant concentrations passing through filtering equipment. However this solution also increases the energy consumption of production facilities.

3. Filtering in machining centers should be improved so that it also retains gaseous air pollutants, reaching the best energy efficiency. When machines are acquired, the need for filtering both particulate and gaseous pollutants must be taken into account. The machining ventilation and air treatment system developed and tested in the project proved to be an efficient means of removing both particulate and gaseous pollutants from the air that is recirculated from a machine tool into the breathing zone. Nevertheless, the system still requires further development and testing in practice at workplaces.

The control of air pollutants is a complex process that is also influenced by many other factors, FIOH says. The exhaust ventilation air flow rates per machining center were often quite low, the study found. If the air flow rate from the machine tool enclosure is too low, it does not prevent pollutants from spreading into the workspace air.

In addition, a low air flow rate causes the accumulation of dirt in ducts consequently posing a risk of fire, for example. Another factor that is significant for workers’ exposure is the regular maintenance of metalworking fluids, including the measurement of endotoxin concentrations in fluids.