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When It's Time to Add a Filtration System

Many engravers who work with lasers are fortunate to be able to vent their lasers to the outside. Actually, the venting of smoke and other combustion fumes is increasingly being banned in many localities not to mention a source of complaints from neighbors. But that’s another story. Of even greater concern to laser engraving and cutting businesses is breathing these fumes in a location with no exterior ventilation. Here, ventless filtration systems are a necessity. Without an adequate filtration system, using a laser would be impossible.

Many laser operators in the USA vent their lasers to the outside using a fairly large blower/exhaust system. The air quality control people, for the most part, have left engraving shops untouched by strict regulations. In Europe, however, this isn’t the case, so an indoor ventless filtration system is required for most lasers. These are more expensive than blowers but bring with them several advantages beyond the obvious.

The AIRDOCK from PAT Technology Systems, Inc. is completely modular, allowing you to change the configuration to fit your needs at any given time.

The AIRDOCK from PAT Technology Systems, Inc. is completely modular, allowing you to change the configuration to fit your needs at any given time.

That being said, the need for indoor filtration systems in the U.S. continues to grow as well with more and more lasers being used in office complexes, manufacturing facilities, malls, at sporting events, etc. Many environments don’t permit outdoor venting for a variety of reasons, the least of which being the property owner doesn’t want 4” holes drilled through their walls or roofs.

If you have attended a tradeshow where working lasers are displayed, you have probably noticed they all have filtration systems connected to their lasers. Some of these laser companies sell the filtration systems while others refer customers to manufacturers of the systems. Occasionally, a laser company will actually offer a system “built in” to their laser such as the VLS lasers offered by Universal Laser Systems, Scottsdale, AZ. I did a full review of the VLS (Versa Laser System) and its HPDFO (High Power Density Focusing Optics) lens when it first came out in the May 2006 issue of EJ.

This is a popular unit from BOFA Americas, Inc. Called the AD Base 2 Oracle, it allows most desktop lasers to sit on top of it to save valuable floor space.

This is a popular unit from BOFA Americas, Inc. Called the AD Base 2 Oracle, it allows most desktop lasers to sit on top of it to save valuable floor space.

There are a number of filtration manufacturers in the U.S. and around the world. For our purposes, we will consider six companies that are well-known and involved in our industry. See the sidebar accompanying this article for a list and contact information.

Why Use a Filtration System?

Lasers can expel some pretty deadly gases and particles when engraving and cutting certain materials. The word “deadly” here is not used lightly. Depending on the material being lasered, everything from cyanide to benzene and formaldehyde to toluene are exhausted. Many of these gases and particles are odorless. OSHA, the Occupational, Safety and Health Administration, has identified over 200 such agents that can cause asthma and even cancer.

Carnegie Mellon University’s Environmental Health and Safety Department has done extensive research to find what kinds of particles and gases are created when various materials are lasered. Some of these are listed in the chart accompanying this article. To learn more, visit their website at www.cmu.edu/ehs.

Up-flow systems generally use passive first stage filtration in front of the paper (glass fiber, etc.) filter. This allows the heaviest particles to drop out of the air stream by gravity. Illustration courtesy of BOFA Americas, Inc.

Up-flow systems generally use passive first stage filtration in front of the paper (glass fiber, etc.) filter. This allows the heaviest particles to drop out of the air stream by gravity. Illustration courtesy of BOFA Americas, Inc.

Obviously, these gases and particles can’t be exhausted into a work environment because of the potentially deadly consequences. It’s bad enough that we dump all this stuff into the atmosphere when we vent our lasers to the outside.

The responsible solution to this problem is to filter the exhaust of our lasers so the gases and various particles are trapped and either neutralized or disposed of properly. Thus, the need for a good filtration system.

If you are interested in a more detailed description of the gases and particles and how they can affect our bodies, check out “What You Should Know About Laser Filtration Systems” in the Sept. 2010 issue of EJ.

BOFA Americas, Inc. offers a control panel with real time indication of filter consumption along with speed indicators, adjustments and more.

BOFA Americas, Inc. offers a control panel with real time indication of filter consumption along with speed indicators, adjustments and more.

How Does a Filtration System Work?

In the most basic terms, all filtration systems work the same way. Some are more powerful than others and some offer unique features the others don’t but in the most simplistic terms possible, they work pretty much the same.

Filtration systems have multiple “stages” of filtration. Each stage is responsible for handling a specific job. The first stage removes the largest particles. This is either handled by gravity which allows the largest particles to “drop” out of the airflow into a tray or a system that runs the particles through a very coarse filter that traps them.

Next is the paper (sometimes foam, glass fiber or a similar material) filter stage. This stage can range from a coarse paper filter to a super fine HEPA filter. In many cases, both types of filters are used in combination. These coarse to extremely fine paper filters can trap particles as small as 0.001mm (many times smaller than a human hair). The smaller the particle the system is capable of catching, the better.

The Filtrabox Expand series laser fume extractor from PAT Technology Systems, Inc. pulls fumes from the laser and purifies the air using three independent filters.

The Filtrabox Expand series laser fume extractor from PAT Technology Systems, Inc. pulls fumes from the laser and purifies the air using three independent filters.

Finally, there is the odor problem. Many of the materials we cut or engrave stink. For me, cutting acrylic is the worst. Even with a good blower to the outside, it still gives me a headache. That means the blower isn’t exhausting all of the odor (odor is actually caused by super-fine particles in the air).

To deal with odors, a filtration system passes the exhaust through a large charcoal filter. The activated charcoal actually absorbs the odors. Again, the more charcoal the odor must pass through, the more odor is absorbed. In addition, the more time that air remains in the charcoal filter, the better. Obviously, the more odor absorbed, the better the system.

So Which System Is the Right One To Buy?

Oh, if only we had a crystal ball. Unfortunately, we don’t. Selecting one model over another can be difficult. There are many models, features, options and sizes. What I can do, is offer some explanation as to what to look for when considering such a purchase. To do that, let’s consider the various features offered by some of the leading companies.

COST: Laser filtration systems range from about $2,000 to $10,000 and more. The temptation to buy based on cost, however, is a poor one. Buy the system that will meet your needs both now and in the future. Searching out a unit that doesn’t have features you don’t need might help keep the cost down but be careful since, as you eliminate features, you might be making your system more difficult to use or service.

The one element you should consider in the “cost comparison” is the cost of replacement filters. A system that meets your needs and has affordable filters will save a lot of money over the lifespan of the system. Selecting a system that removes as much particulate as possible in the first stage, either by gravity or by filter, is one way to greatly extend the life of the other more expensive filters.

Down-flow filtration systems generally use a pleated filter made of paper, glass fiber, etc., to catch the big particles and serve as a first stage of filtration. Illustration courtesy of Universal Laser Systems.

Down-flow filtration systems generally use a pleated filter made of paper, glass fiber, etc., to catch the big particles and serve as a first stage of filtration. Illustration courtesy of Universal Laser Systems.

PRE-FILTERS: As the name suggests, these filters are first in line. Their task is to capture as much of the big stuff as possible. This is done by using a coarse filter material which can be made of a variety of materials including paper and glass fiber that is folded many times over itself so as to make the filter as large as possible. This is the least expensive of all the filters used and the one that is replaced most often. If this filter does its job, it will greatly extend the life of the other filters in the system.

Some filtration systems use a pre-filter that captures and holds the largest particles so they can be dumped while other designs drop the largest particles into a tray at the bottom of the system that can be removed and dumped.

PASSIVE PRE-FILTERS: Some systems have a “passive” first filter. Basically, this means there is a void at the bottom of the cabinet where the heaviest particles can just drop out of the air stream and land in a tray in the bottom of the cabinet.

UP-FLOW VS. DOWN-FLOW DESIGN: You will find some systems have the air inlet at the top of the device while others have it at the bottom. The up-flow systems (the inlet is at the bottom) I have looked at are designed that way to provide a passive pre-filter. Opinions vary as to which is the best design.

REVERSE AIRFLOW TECHNOLOGY: BOFA systems use a reverse airflow technology to extend the life of the filters. Since filters clog up over time with the particles they remove from the airflow, it seems a logical step to be able to push air back through the filter to “clean it.” This doesn’t eliminate the need to replace filters but does help keep them open so air can flow more freely and thereby extend their life.

HEPA FILTER: The system you choose should have a HEPA filter. This device is responsible for removing the really tiny particles from the air stream. Lasers put off a lot of very tiny particles, often in the form of smoke. These can’t be trapped in ordinary paper filters. A HEPA filter can handle particles down to 1 micron. (BOFA says their carbon filter can capture 99.997% down to 3 microns and 95% down to 1 micron.)

Some Universal Laser Systems lasers like the VLS2.30 are available with a custom laser fume filtration system stacked beneath the laser, making a single piece.

Some Universal Laser Systems lasers like the VLS2.30 are available with a custom laser fume filtration system stacked beneath the laser, making a single piece.

CHARCOAL FILTER: Any system you consider should have an activated charcoal filter included. Charcoal filtration, sometimes referred to as a chemical filter, works to eliminate odors. To be effective, air must remain in the charcoal for an extended time. This gives the charcoal time to actually absorb the odors and other hazardous fumes. It is important that this, and all, filters are sealed so air cannot escape around the filter or push its way through the charcoal (called tunneling) without remaining in contact with the charcoal for the prescribed amount of time. Most manufacturers use 40 lbs. of activated charcoal in each unit. PAT Technology Systems, manufacturers of “Filtrabox” systems, offers a filtration unit that has two charcoal filters with each one having 20 lbs. of activated charcoal. Some of the really large systems, of course, use more and if you plan to run multiple lasers with the same filtration system or you are running an unusually large laser or cutting certain materials, you might want to consider finding a system with larger charcoal filters. Most of us, however, should be happy with 40 lbs.

ELECTRONIC DISPLAY: Controls for these systems range from an on/off switch to a complete diagnostic capability you can monitor from anywhere on your cellphone. Although the cellphone concept might be overkill for most of us, it is helpful to have some diagnostic ability with these systems. One company offers colored LEDs that show when each filter is approaching replacement time and when it needs replacing. Another company offers a control panel that displays a graphic showing how “used up” each filter is, the amount of airflow, number of hours on the machine, etc.

CFM REQUIREMENT: Each unit is rated in one of two ways (or both). In the U.S., we generally refer to airflow in CFM (cubic feet per minute). In other parts of the world, it is rated by m3/h (cubic meters per hour). The conversion from m3/h to CFM is 1 m3/h = 0.58858 CFM or, for a quick comparison, it is 1 = 0.6.

The amount of CFM a filtration system can develop is significant and should be matched carefully with the specifications of each laser. To underrate a laser means the filtration either isn’t going to be adequate or the filters are going to require more frequent replacement. A few small lasers, such as Universal Laser’s VL series, are rated for about 250 CFM but most small lasers call for 350-400 CFM. The larger the laser, the more exhaust it will require. It is common for a 36”-48” laser to require 750 CFM or more.

The LPH400 from Quatro Air Technologies Inc. includes a reinforced table to save space and front door filter access.

The LPH400 from Quatro Air Technologies Inc. includes a reinforced table to save space and front door filter access.

FLOW CONTROL: Some systems allow you to control the amount of airflow that goes through the device. This is helpful when the system you choose produces more CFM than your laser(s) calls for. Reducing the airflow reduces air noise and extends the life of the filter media. For this feature to be effective, it is important to have a device that displays what the actual amount of airflow is in real time. This is not something to guess at and, as the filters age, the amount of air that can pass through them declines. Without a way to accurately read this, you will likely run the system too slow, which doesn’t let it do its job, or too fast, which shortens the life of the HEPA filter. This feature is also helpful when running multiple lasers through a single filtration system as the volume of CFM will need to be changed when multiple lasers are running vs. reduced when only one laser is running.

MULTIPLE VOLTAGE CAPABILITY: Most places in the U.S. will provide 110-120 volts and 220-240 volts of power supply, and most people will run their lasers and filtration systems at 110-120 volts. Some areas, however, struggle to maintain a consistent voltage power supply. This can easily damage equipment by running the power supply and motor at a voltage that is too high or too low. Especially overseas, there can be a hodge-podge of voltages. Most of Europe is 220 volts and most lasers and filtration systems offer both standard voltages, but if there is any chance you might take your equipment on a sightseeing tour of the world, or the area where you live struggles to maintain consistent voltages, it is nice to have an automated voltage selector on your filtration system that can detect the actual voltage (not just what it is supposed to be) and adjust accordingly. BOFA filtration systems, for example, offer the ability to run from 90 to 275 volts.

In addition, don’t forget that most of the U.S. runs 60 cycle AC voltage. Many other countries run 50 cycles. Running the wrong cycle rating can and will damage equipment. Most systems are designed to run on both but check to be sure.

The Model 300 laser fume extractor from Sentry Air Systems, Inc. is available in a portable version that includes heavy-duty casters and a portability handle for those who take their lasers off-site.

The Model 300 laser fume extractor from Sentry Air Systems, Inc. is available in a portable version that includes heavy-duty casters and a portability handle for those who take their lasers off-site.

ELECTRICAL REQUIREMENTS: Regardless of what voltage arrangement you use, filtration units pull a lot of power. Some brush up against 20 amps which is the limit of most 110-120 volt breakers. This means you will probably need a separate circuit that is dedicated to run your filtration system. Plugging in both your laser and filtration system into the same outlet probably will trip the circuit breaker. To determine this, add the number of amps listed for your laser(s) and for the filtration system. If the total is close to 20, you will need multiple circuits.

NOISE: Filtration devices include a motor and they are pulling a lot of air. Both make noise. The question is: How much noise? Noise is measured in dBs (decibels). The more dBs, the more noise. When added to the noise of one or more lasers, and perhaps a rotary engraver or two, the noise level can be uncomfortable. Most filtration systems create 55-65 dBs of noise. This seems to be pretty consistent across the industry but it is important to consider. Of course, the larger the unit, the more noise it will create.

DIGITAL VS. STANDARD MOTORS: The types of motors (blowers) used in these systems varies but they fall into two categories: standard brush motors and digital motors. Brush motors, like we have all used for 100+ years, are less expensive but they have something called “brushes” that brush up against the armature to transfer electricity. These brushes eventually wear out and have to be replaced. Digital motors cost more but don’t have brushes to deal with. If you are going to run your system 24/7, the difference in cost is certainly merited but for normal use, the need to replace brushes probably will never happen so it is an option that you can justify either way. Yes, a digital motor is, in my opinion, better. It puts out less RF, runs quieter and cooler, and should last longer without attention, but you will have to decide if the difference in cost is worth it to you.

BASE UNITS: Some units, such as the BOFA AD Base 1 Oracle, the ULS 2000 and the Purex Ebase units, are designed for a laser to sit on top of them. This is limited to the smaller lasers but greatly reduces the footprint of the unit by combining the two pieces of equipment. If your space is at a premium, a “base” unit might be helpful.

LASER INTERFACE: Some units come with an electrical interface that connects with your laser so when you turn on your laser, the filtration device activates as well. Although you might think of this as just a convenience, it is also a safety feature that ensures the operator never forgets to turn it on and endanger their health.

SHIPPING: Most filtrations systems adequate for our industry are heavy—at least 100-200 lbs. or more (the charcoal filter weighs 40 lbs by itself). This means they have to be shipped by a truck service, such as FedEx or UPS, and it can be a headache in some cases. Filtration units that weigh 100 lbs. or more can weigh much more when shipping cartons are added and can be difficult to handle, even with a liftgate on the truck. Most of us don’t have shipping docks so heavy deliveries must be carefully scheduled.

Filtrabox (PAT Technology Systems) has come up with a unique solution with what they call an “AIRDOCK.” This is a filtration system that is totally modular. This means it can be broken down into components and shipped using regular UPS.

The FumeBuster from Purex Inc. is a 3-stage laser fume extraction system.

The FumeBuster from Purex Inc. is a 3-stage laser fume extraction system.

SERVICE: Like lasers, service and support is everything. The companies reflected in this article have been around a long time and have a long-standing reputation. To buy systems online from eBay or Amazon, not to mention Asia, can be very risky. A $2,000 system isn’t worth much if you can’t find replacement filters or it doesn’t perform adequately. Use discretion when buying by remembering service and support is everything.

WARRANTY: The warranty for a filtration system varies depending on the manufacturer. I couldn’t find warranty policies on most websites so be sure to ask about both the standard and extended warranties. Warranties won’t cover filters, but there is also a fairly expensive blower motor and some electronics in these devices. You want to be sure those are protected.

There are, of course, other considerations but most of them are for more industrial applications than what engravers need. One is the ability to filter volatile organic compounds (VOCs). This should not be necessary for engravers since we should not be messing with VOCs to start with. The same is true with filtration units designed for PVC. Although companies make units suitable for filtering polyvinyl chloride, our lasers should not be used for engraving PVC as it is highly toxic not to mention extremely corrosive and will quickly destroy metal laser parts.

One feature which might be nice but is certainly not mandatory for most of us is the ability to place a small air compressor (for air assist) inside the filtration cabinet just to get it out of the way and perhaps reduce some of the noise.

My best advice is first, take your time and talk to company representatives but also their customers. Ask lots of questions and keep a notebook with the answers so you can make comparisons afterward. Second, go with a major, well-known company in the industry, one that has service capabilities near you if possible. Third, be sure replacement filters are easy to locate and purchase. Johnson Plastics Plus, for example, carries some BOFA filters. If you already have an account with them, it makes ordering much easier.

Finally, take the time, energy and money necessary to maintain your system properly. These systems don’t require much maintenance but when filters are clogged, they can allow contaminates into your workspace and cause serious health issues.

And the good news is… A good filtration system can last decades when given the proper care. They require an investment in the beginning but if you buy a quality device, you might never have to buy another.

When It's Time to Add a Filtration System
J. Stephen Spence

Copyright © 2020
As Printed in March 2020, Volume 45, Number 9, The Engravers Journal

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