Dealing with HCL Acid in PVC lasing
When laser marking, cutting or engraving PVC, attention needs to be made with regards to the Hydrogen Chloride gas which is released in the subsequent plume of laser fumes. The gas has an occupational exposure limit of just 1ppm (part per million) over an 8 hour period. It is also highly corrosive and can eat away at not only the laser itself but the internal electronics of any purification system.
So how should a fume extraction system be built to cope with such a fume?
Many companies have designed a system based upon reverse airflow, instead of fume entering from the top down, it is sucked upwards through the filters. This immediately stops any HCL from dripping onto components from above. A pre filter must be installed, an option to have this coated in a neutralising chemical (strong alkali) would be idea; although generally a chemical media is applied after the HEPA, which is sufficient. The acid will also react to the bare metal surfaces of the extraction unit housing, and so must be coated in an epoxy or paint that is resistant to the HCL effects. If any part of the system fails through HCL corrosion, there needs to be a fool proof mechanism that alerts the users that HCL gas is being released back into the atmosphere. Most laser purification systems have a VOC sensor but this is inadequate for HCL, which requires a seperate device. Ideally the sensor should be linked with a shut off to the laser itself so production of any harmful fumes is immediately stopped.
