Laser Generated Airborne Contaminants

09 January 2012
Laser Generated Airborne Contaminants

In an article, the Laser Institute of America discusses the considerations of dealing with fumes generated by laser processes.

Lasers are commonly used to mark, etch, cut and weld a wide variety of materials in automotive plants, packaging lines, medical procedures, aerospace manufacture and many other applications. It seems that there is a new use for lasers every day. Lasers can offer an alternative to traditional processing methods. If coupled with the right Local Exhaust Ventilation (LEV) systems, lasers deliver excellent results in terms of precision, machining time, flexibility and performance. To comply with international health & safety regulations, LEV’s are required or recommended for use with most laser operations in order to protect personnel and to enhance the performance of the laser system itself.


What happens in laser processing?
When a laser beam is applied to the surface of a material, several conditions can occur. High temperatures that are generated cause the air near to the contact point to expand, generally back in the direction of the lens. The laser beam causes incineration, vaporization, melting and softening of the target substrate. Rapidly expanding gases pick up and carry the removable particles and droplets at relatively high velocities away from the substrate. The contaminants released consist of a wide variety of gases, in some cases noxious i.e., benzene, phosgene. They also consist of the products of complete and partial combustion including possible oxides of the base material. Stainless steel, for example, releases Chromium and Nickel, which can cause chronic toxicological effects such as liver/kidney disease and cancer.

It is critically important that you are aware of the emissions produced during your specific application as many laser processes produce extremely harmful and even toxic fumes. The following is a list provided by Purex, who manufactures digital and analog fume extraction solutions for laser applications.

Common Substrates, and LGACs

Non-Metals

Material

Emissions

Other emissions

Kevlar

Respirable dust

Benzene, HCN, No2, PAHs

Polycarbonate (PC)

Respirable dust, Cresol

Phenol, Benzene

Polyamide (PA)

Respirable dust, Methanal

1,3-Butadiene, PAHs, Propenal, Benzene

Polypropylene (PP)

Respirable dust

1,3-Butadiene, Propenal, Benzene

Polyethylene (PE)

Respirable dust

1,3-Butadiene, Propenal, Benzene

Poly (vinyl chloride) (PVC)

Respirable dust, HCL

Benzene, Methanal, PAHs, Phosgene

Rubber (SBR-man made)

Respirable dust, 1,3-Butadiene

Styrene, PAHs, Propenal, Benzene

Polyester (PET)

Respirable dust

Benzene, Toluene, Ethylbenzene

Polystyrene (PS)

Respirable dust, Styrene

Benzene, Toluene, PAHs

Polyurethane (PU)

Respirable dust

Benzene, Toluene


Metals

Material

Significant emissions

Mild steel

Iron oxide, NO, NO2, CO

Stainless steel

Chromium, Nickel

Galvanised steel

Zinc Oxide

Tool steel / Hastelloy

Vanadium, Cobalt

Nimonics

Cobalt, Chromium, Nickel

For an expanded list: Contact richard.riffner@purex.co.uk  630-465-2412

There are a number of important items to take into consideration when evaluating LEV’s for your application. Use these as a baseline when evaluating solutions.

Flow Control

Over time filters become saturated and blocked from captured particulate. As blockage occurs, the flow rates may drop and if not manually monitored, gases/particulate will not be captured and eliminated. LEV’s with intelligent Flow Control automatically monitor airflow and adjust motor speed to keep the extraction rates at the required speed throughout the life of the filter. This ensures proper air quality while preventing downtime and expensive damage to equipment caused by loose particulate.

Air Monitoring

How do you know that your system is capturing what it should? Consider a solution that provides feedback and insures that the air returning to your workplace is safe.

Filter Status

It is important to change filters when needed or you risk having an LEV that no longer operates at the optimum level. On the flip side, changing them too soon can be expensive. Look for a system that provides feedback regarding filter status which produces a safe work place while reducing filter costs..

OSHA citations have now been issued relative to lasers using the authority vested under the “general duty clause” of Public Law 91-596; the Occupational Safety and Health Act of 1970. Once you pinpoint the emissions produced in your process and integrate an ample LEV, you can help insure the safety of your workplace while extending the life and up-time of your laser systems.