Unit 3, Basepoint
Abbey Park Ind Est
Premier Way, Romsey
Hants, SO51 9AQ
Tel: 023 8081 5384
Email: [email protected]
Web: www.vodex.co.uk
Laser Fumes
ADVICE AND INFORMATION RELATING TO THE PROBLEMS
ASSOCIATED WITH LGAC'S (Laser Generated Air Contaminants)
Lasers are now an essential tool in industry for cutting, marking, engraving and welding a vast range
of materials. Metals are the most commonly worked substrate but organic materials (plastics, paper,
wood) are catching up fast.
In virtually all the above operations some form of fume is given off as the laser thermally decomposes
the substrate to a greater or lesser degree. This fume is a mixture of particulate and gaseous matter.
Fume from materials such as metals and glass is mainly particulate, the majority of which is less than
1µ (micron) in diameter. Organic materials, particularly plastics, produce much more complex fumes
which are investigated below.
The particle size distribution of the airborne particles is shown on graph 1 (above) and with small
variations relates to the majority of polymers. Most of the particles are spherical and roughly 90% by
weight are less than 1µ in diameter. These particles fall within the respirable range and need to be
removed from the working environment to prevent bronchal or lung damage. The gaseous organic
compounds produced are known as Volatile Organic Compounds, VOC's.
The VOC's produced are a mixture of the following:

Aliphatic hydrocarbons: alkane, alkene

Aromatic hydrocarbons: benzene, toluene, xylene

Aldehyde: formaldehyde

Polycyclic aromatic hydrocarbons: benzo(a)pyrene
Additionally some materials have other specific groups e.g. PVC polymers generate HCl, 2
component epoxy polymers yield amines and PET generates THF.
A considerable number of the above have Occupational exposure limits set for them and these are
detailed in the Operator health section. As with the particulate element these gases need removing
from the workplace.
Vodex Limited – Registration Number 4812548, Unit 3 Basepoint , Abbey Park Industrial Estate, Premier Way, Romsey, Hants, SO51 9AQ
Unit 3, Basepoint
Abbey Park Ind Est
Premier Way, Romsey
Hants, SO51 9AQ
Tel: 023 8081 5384
Email: [email protected]
Web: www.vodex.co.uk
Problems Caused by LGAC's
(Laser Generated Air Contaminants)
Effects of Fume
There are three main areas of consideration associated with the fume:
Health issues - the effects it may have on the workforce coming into contact with it
Laser efficiency- the effects on the laser optics
Product contamination- the effects on the products being lasered
Health issues
These particles fall within the respirable range and need to be removed from the working environment
to prevent bronchial or lung damage
Particulates
The particulate generated in most laser applications is sub micron in size and as such almost all is
respirable. This gives rise to two separate concerns:
Dust of any kind can also become a substance hazardous to health under COSHH when it is present
at concentrations in the air equal to or greater than 10 mg/m3 (as a time weighted average over an 8hour period) of inhalable dust or 4 mg/m3 (as a time weighted average over an 8 hour period ) of
respirable dust. Marking applications typically generate up to 1mg/s of fume and Cutting applications
in excess of 10 mg/s.
The second is a reaction to the actual material of the particulate which may cause allergic,
carcinogenic or toxic effects e.g. chrome and nickel compounds released from stainless steel are
thought to be carcinogens.
Vodex Limited – Registration Number 4812548, Unit 3 Basepoint , Abbey Park Industrial Estate, Premier Way, Romsey, Hants, SO51 9AQ
Unit 3, Basepoint
Abbey Park Ind Est
Premier Way, Romsey
Hants, SO51 9AQ
Tel: 023 8081 5384
Email: [email protected]
Web: www.vodex.co.uk
Gases
Potential problems are usually associated with plastics which give off Volatile Organic Compound's
when lasered, most of which have associated Occupational Exposure Limits (OEL). The table below
covers a range of common plastics and lists the VOC's given off together with their OEL. PVC is worth
a special mention in this context since it releases hydrogen chloride and small amounts of phosgene
both of which are extremely toxic.
Laser efficiency
The optical system of the laser is susceptible to damage from particulate getting burnt onto the lens
which reduces the laser efficiency and on marking applications can effect the quality of the code.
Additionally particulate in the laser beam can refract/reflect the light which diffuses the beam (see
animation opposite).
Product contamination
Marking applications on open containers are vulnerable to particulate settling in the container which
contaminates the product being filled.
Exposure limits
OEL (8hr) mg/m3
Benzene
9
1,3 Butadienne
22
Formaldehyde
2.5
Methylmethacrylate
208
Phenol
20
Creois
22
Toluene
191
Hydrogen chloride
2
Phosgene
0.08
Methylamine
13
THF(Tetrahydrofuran)
300
Vodex Limited – Registration Number 4812548, Unit 3 Basepoint , Abbey Park Industrial Estate, Premier Way, Romsey, Hants, SO51 9AQ
Unit 3, Basepoint
Abbey Park Ind Est
Premier Way, Romsey
Hants, SO51 9AQ
Tel: 023 8081 5384
Email: [email protected]
Web: www.vodex.co.uk
Lasing Polymers
When a component is lasered an amount of the substance is thermally decomposed (burnt off). This
thermal decomposition, which is the fume, comprises a mixture of particulate and gas. Glass, ceramic
and most base metals do not generate as much fume, so we will concentrate on polymers which do.
The gaseous organic compounds are known as Volatile Organics Compounds, VOC's. The table
below shows the ratio of particulate to gas for a variety of plastic materials.
Non organic gases given off, that need capturing, tend to be acidic eg HCI and for these applications
a specifically designed media for acid gases is included in the gas filter. Click here for further
information on acid gases applications.
The chart below gives a breakdown of the various chemical compounds produced when lasering
various polymers.
The above table shows the ratio of Particulate to gas for a variety of plastic materials.
Yag laser coder by Alltec >
< Laser Marking system by Markem
Laser coding system by Telesis Eagle
Vodex Limited – Registration Number 4812548, Unit 3 Basepoint , Abbey Park Industrial Estate, Premier Way, Romsey, Hants, SO51 9AQ
Unit 3, Basepoint
Abbey Park Ind Est
Premier Way, Romsey
Hants, SO51 9AQ
Tel: 023 8081 5384
Email: [email protected]
Web: www.vodex.co.uk
Lasing PVC
When PVC is burned during the lasering process the extremely corrosive, acidic Hydrogen Chloride
or HCL is produced. It is imperative that this fume is removed quickly and efficiently for both the safety
of the operators and to protect the laser and surrounding equipment.
Protecting Personnel
HCL is classed as a major health hazard, and as a result has a maximum exposure level of 1ppm
(Part Per Million) over an 8 hour period. (from HSE EH40/2000 Occupational Exposure Limits).
Protecting the Laser
Not only is HCL a major hazard to health but it is also extremely corrosive. If this acidic fume is
allowed to migrate onto the laser lens housing and associated components it will, over a period of
time, cause irreversible corrosive damage.
Now we have established the problems that lasing with PVC can cause, we can look at how to extract
the fume safely without damage to the extractor.
First of all it is imperative that all internal contact parts are lined in an acid resistant coating. The PVC
upgrades available on the BOFA Advantage units have a specially developed 2 part epoxy for this
purpose.
Next we come to filtration. The 2 stage pre filters used in the Advantage extractors are completely
sealed. This is a very important factor as the fume that enters the pre filter chamber will drop in
velocity separating the liquids into the sealed sump. Some extractors have absorbent pads to soak up
this liquid. These pads rest directly under the pre filter bags that make it both very difficult and
dangerous to handle on filter change.
Any of the HCL that passes through the 2 stage pre filter and HEPA filter will be absorbed within a
layer of media that is specifically designed to absorb and neutralise the HCL gas.
Advantage units fitted with the PVC upgrade have an HCL sensor mounted within the exhaust of the
system. This unit is specific to HCL and will only be activated when HCL is detected. Many extraction
systems are fitted with gas detection sensors but these are normally for VOC (Volatile Organic
Compounds) and will not be activated by HCL. It is advisable to check with the manufacturer of the
extraction system to make sure an HCL sensor is fitted.
Laser coding systems by Linx Xymark
YAG laser marker by Alltec
Laser coded PVC product
Vodex Limited – Registration Number 4812548, Unit 3 Basepoint , Abbey Park Industrial Estate, Premier Way, Romsey, Hants, SO51 9AQ
Unit 3, Basepoint
Abbey Park Ind Est
Premier Way, Romsey
Hants, SO51 9AQ
Tel: 023 8081 5384
Email: [email protected]
Web: www.vodex.co.uk
Laser Welding
Laser welding of plastics and metals are now common place. Most welding of plastics only softens or
melts the substrate bonding them together rather than burning. As a result no actual fume is
generated, but some plastics may produce an unpleasant smell. Welding metals however can
produce hazardous fume, especially if they are anti corrosion coated such as Zintac.
A variety of toxic fumes and particulates are generated when different substrates are being lasered.
These contaminates are known within the industry as LGAC's (Laser Generated Air Contaminates).
LGAC's of different makeup can react in the extreme within the filter separation process.
With this knowledge, Bofa have developed the Advantage range of fume elimination systems
designed specifically for such a broad base of lasered substrate materials.
Laser Marking system by Markem
Vodex Limited – Registration Number 4812548, Unit 3 Basepoint , Abbey Park Industrial Estate, Premier Way, Romsey, Hants, SO51 9AQ
Unit 3, Basepoint
Abbey Park Ind Est
Premier Way, Romsey
Hants, SO51 9AQ
Tel: 023 8081 5384
Email: [email protected]
Web: www.vodex.co.uk
Laser Cutting
Cutting of materials such as metals, plastics and textiles are now commonly achieved using lasers.
This has great benefits such as fast, clean and accurate cuts that often don't require any additional
finishing. Laser cutting does however produce an enormous amount of hazardous contaminants that
need to be removed to protect the operator and ensure the quality of cut. As with all laser applications
if the fume is not removed at source using LEV (Local Exhaust Ventilation), the fume can blur the
laser beam, affecting its efficiency.
A variety of toxic fumes and particulates are generated when different substrates are being lasered.
These contaminates are known within the industry as LGAC's (Laser Generated Air Contaminates).
LGAC's of different makeup can react in the extreme within the filter separation process. In some
instances having high ratio of gases to particulates and visa versa. For example, fume from Nylon
when lasered is roughly 80% particulate to 20% gas, where as fume from Acrylic is 90% gas to 10%
particulate.
With this knowledge, Bofa have developed the Advantage range of fume elimination systems
designed specifically for such a broad base of lasered substrate materials.
Laser cutting system by LPKF
Vodex Limited – Registration Number 4812548, Unit 3 Basepoint , Abbey Park Industrial Estate, Premier Way, Romsey, Hants, SO51 9AQ
Unit 3, Basepoint
Abbey Park Ind Est
Premier Way, Romsey
Hants, SO51 9AQ
Tel: 023 8081 5384
Email: [email protected]
Web: www.vodex.co.uk
Laser Engraving
Lasers are being used more and more as a replacement to conventional engraving systems. Laser
engravers offer higher speeds and accuracy. When used in conjunction with an efficient fume
elimination system and LEV (Local Exhaust Ventilation) extraction kit, the user benefits from a much
cleaner working environment.
A variety of toxic fumes and particulates are generated when different substrates are being lasered.
These contaminates are known within the industry as LGAC's (Laser Generated Air Contaminates).
LGAC's of different makeup can react in the extreme within the filter separation process - In some
instances having high ratio of gases to particulates and visa versa.
For example, fume from Nylon when lasered is roughly 80% particulate to 20% gas, where as fume
from Acrylic is 90% gas to 10% particulate. With this knowledge, Bofa have developed the Advantage
range of fume elimination systems designed specifically for such a broad base of lasered substrate
materials.
Laser Marking system by Markem
Vodex Limited – Registration Number 4812548, Unit 3 Basepoint , Abbey Park Industrial Estate, Premier Way, Romsey, Hants, SO51 9AQ
Unit 3, Basepoint
Abbey Park Ind Est
Premier Way, Romsey
Hants, SO51 9AQ
Tel: 023 8081 5384
Email: [email protected]
Web: www.vodex.co.uk
Filtration
Most laser fume purification systems have 3 stages of filtration. A pre filter to protect the higher cost
HEPA (High Efficiency Particulate Air) for the finer particulates and finally a gas/chemical filter.
Pre Filters
The efficiency of the pre filter is directly related to the life of the HEPA in that the more particulates
captured in it, the less can pass through and prematurely block the HEPA. Most pre filters have an
efficiency grading of F5 - F7. When plastics are being lasered, the particulate size generated is
typically 0.2microns. At this level of filtration the media has an efficiency of 35% in F5 to 65% in F7.
When metals are being lasered the particulate size being generated is typically below 1micron. This
equates to an efficiency of 65% in F5 to 80% in F7.
The Bofa Advantage range of laser fume purification systems has an F8 grade media which gives an
efficiency of 80% at 0.2 microns and 95% at 1micron.
Pre filters most commonly come in 2 styles: Panels and Bags
Panels
Most panel filters have a nominal depth of 50mm. They have few pleats to obtain some increase in
surface area. In short we would not recommend the use of this type of filter in any laser marking or
cutting exercise as the surface areas are far too small for the amounts and the size of particulate
generated.
Bags
Bag filter are commonly used in laser fume elimination for their volumetric containment properties.
These bags have a variety of shapes including multi pocket styles to increase surface area and
reduce pressure drops.
Vodex Limited – Registration Number 4812548, Unit 3 Basepoint , Abbey Park Industrial Estate, Premier Way, Romsey, Hants, SO51 9AQ
Unit 3, Basepoint
Abbey Park Ind Est
Premier Way, Romsey
Hants, SO51 9AQ
Tel: 023 8081 5384
Email: [email protected]
Web: www.vodex.co.uk
The BOFA 2 Stage Filter (Deep Mini Pleat Cartridge)
As the contaminated air enters the inside of the cartridge chamber, the velocity drops slowing down
the airflow causing in the larger and heavier particulates to fall within the cartridge sump. The sump
also allows larger particulates that build up during operation to drop away from the filter through the
true nature of reverse airflow design. See fig 1.
Surface area and depth of media
Filter life is directly related to surface area. As previously mentioned the larger dry particulates build
up and fall away during operation. Sticky particulates on the other hand will hit the media surface and
dry on contact irrespective of the progressive depth of the media. The end result of this is skinning or
masking off to the surface media. Therefore the greater the surface area the longer the filter will last.
Electrically Charged Media
It should be worth mentioning at this point that electrostatic charged fibres have in recent years been
applied to a range of panel and bag filtration products. Extensive field trials have shown that the
charged fibres are adversely affected and the charge can to a large extent be negated by humidity or
by coming into contact with carbonaceous contaminants. This can result in a severe decrease in
efficiency after a few weeks operation. The particles are held within a much more open matrix, in the
event of vibration caused by air movement through the filter, particles can become dislodged and
carried into the 'clean' airstream.
All pre filters used in the BOFA Advantage range have a very high degree of particulate separation
(F8, which is 95% @ 1 micron). The Advantage 180 and 400 having 9m2 of surface area and the
1500 and 4000 being as high as 20m2. The whole filter is designed as a cartridge with a sump
capacity of 10Kgs for the 180 and 400 series and 25Kgs for the 1500 and 4000 series. Where bag
filters are used in conjunction with a reverse airflow system the whole bag acts as the filter. This
results in larger particulates falling back within the filter media itself. If that media is pleated, the
surface area for fall back contaminants can lay in up to 50% of the construction of that filter. See fig 2.
Multi pleat bag filters are used to obtain greater surface area within the media. In cases where these
filters are positioned horizontally being supported by a vacuum inlet pipe secured through it centre,
the pleats tend to collapse masking off large sections thus nullifying the effectiveness of the design.
This problem is magnified where more pleats are added.
Vodex Limited – Registration Number 4812548, Unit 3 Basepoint , Abbey Park Industrial Estate, Premier Way, Romsey, Hants, SO51 9AQ
Unit 3, Basepoint
Abbey Park Ind Est
Premier Way, Romsey
Hants, SO51 9AQ
Tel: 023 8081 5384
Email: [email protected]
Web: www.vodex.co.uk
Micro Filtration
Most micro or HEPA filters used today are of the mini pleat design. They are generally manufactured
by specialist filter companies to ensure that the latest manufacturing and test methods are adopted.
Each filter incorporates a series of webbing between the pleats. This feature not only guarantees
even spacing for full filter coverage between each pleat, but also alleviates the possibility of airflow
vibration or collapse.
Filters should be individually tested and certified to a minimum efficiency of 99.997% down to 0.3
microns and 95% as small as 0.1 micron.
The Bofa Advantage micro filters are positioned within the system in such a way that all the
particulates are not only captured but held within the media. This is not the case with conventional
reverse airflow systems were particulate can fall away and rest on the outside of the pre filter creating
a health risk on filter replacement.
Mini pleats can be produced with depths of up to 200mm within each pleat, depending on the
application.
Gas/Chemical Filtration
Most standard chemical filters are made up of a 50/50 mix of Activated Aluminium Potassium
Permanganate and Active carbon. The media neutralises a broad base of chemicals and VOC
(Volatile Organic Compounds) pollutants. Where PVC is lasered a third gas media should be
introduced that is specifically designed to absorb and neutralise harmful and extremely corrosive HCL
(Hydrogen Chloride) gas.
2 stage pre filter cartridge
ADCF (ADVANTAGE Combined Filter) Small Filter
Vodex Limited – Registration Number 4812548, Unit 3 Basepoint , Abbey Park Industrial Estate, Premier Way, Romsey, Hants, SO51 9AQ