Paul Industries designs and installs process exhaust, scrubbing and abatement systems for Oregon’s semiconductor and advanced manufacturing plants. The defining rule of fab exhaust is segregation. A fab does not have an exhaust system; it has four or five of them, deliberately kept apart, because several of the streams a fab produces will react with each other if they are allowed to meet. Combining them to save duct is how a plant creates a hazard that neither stream presented on its own.
Request a quote or call 201-450-8280
Why the streams stay apart
Oregon’s semiconductor sector is the state’s largest manufacturing industry, employing roughly 33,000 people, and the processes involved release acids, solvents, bases and reaction products that have to leave the building safely and lawfully. Segregating them is not fastidiousness; there are three independent reasons for it and each would be sufficient alone.
Chemistry. Acid and ammonia streams meeting in a duct produce salts that deposit and accumulate, progressively restricting the duct and eventually requiring it to be cleaned or replaced. Other combinations are worse. A duct is a confined space full of the reactants and none of the supervision.
Treatability. Abatement equipment is selected for a specific contaminant. A wet scrubber suits acid gases; solvents generally need a different approach entirely. Combine the two streams and neither can be treated efficiently, so the plant ends up over-treating a large combined volume to handle a small problematic fraction. Segregation keeps each treatment system sized for what it actually has to remove.
Materials. Acid exhaust ductwork is built in materials chosen to survive acid, typically fluoropolymer-lined or appropriate plastics. Solvent exhaust has different requirements, including fire considerations. A combined duct has to satisfy every requirement at once and usually satisfies none of them economically.
| Stream | Carries | Usual treatment |
|---|---|---|
| Acid | Acid gases and mists from wet processing | Wet scrubbing with controlled chemistry |
| Solvent or VOC | Organic vapors | Adsorption, thermal or catalytic oxidation |
| Ammonia and base | Alkaline species | Separate scrubbing; never combined with acid |
| General | Nuisance and low-hazard extraction | Filtration where required |
| Heat | Warm air from equipment | Discharge, with recovery where practical |
Wet scrubbing, where most acid exhaust ends up
A wet scrubber works by bringing the gas stream into intimate contact with a liquid that absorbs the contaminant. It is a mature technology and it performs well, and the things that determine whether a given installation performs well are unglamorous.
Contact, not volume. Removal depends on the surface area and time over which gas and liquid interact, which means packing condition, liquid distribution and gas distribution matter more than vessel size. A scrubber with channelled flow is a large vessel doing a fraction of its rated work, and it will pass a visual inspection.
Chemistry control. Absorbing an acid consumes the scrubbing liquid’s capacity, so pH has to be monitored and the liquid dosed and bled continuously. A scrubber running on exhausted liquid does essentially nothing while appearing entirely normal from outside, and this is the commonest cause of an abatement system quietly failing.
Mist elimination. A scrubber generates droplets, and droplets carrying absorbed contaminant leaving the stack defeat the purpose. Mist eliminators are part of the system and they foul, which means access to inspect and clean them should exist.
The blowdown goes somewhere. Scrubber liquid is bled to maintain chemistry and that bleed is a wastewater stream with its own treatment requirement. An abatement project that stops at the stack has moved the problem into the drain.
| Continuous load | Per year | Over ten years |
|---|---|---|
| 50 kW | $35,259 | $352,590 |
| 100 kW | $70,518 | $705,180 |
| 200 kW | $141,036 | $1,410,360 |
Exhaust runs continuously and cannot be turned down without consequence, so this load is genuinely fixed. At Oregon’s 8.05 cents per kilowatt-hour, essentially the national average of 8.13 (EIA, 2024), the saving available is in pressure drop rather than in runtime: duct sizing, fitting selection and keeping filters and packing clean all reduce fan power permanently, and none of them compromise safety.
Make-up air, redundancy and the interlocks
Every cubic meter exhausted must be replaced. A fab exhausts a great deal, and that air has to be brought in, filtered and conditioned, which is frequently a larger energy cost than the exhaust fans themselves. Exhaust design and make-up air design are one problem, and a plant that adds exhaust capacity without adding make-up will find its pressure cascade inverting and outside air arriving through whatever gap it can find.
Redundancy is a safety requirement here. If exhaust stops while a process is running, a tool room can become unsafe quickly. Redundant fans, automatic changeover, and emergency power on the systems that genuinely need it are part of the design case rather than an upgrade.
Interlocks that actually stop the process. Loss of exhaust flow should stop the tools it serves, automatically and provably. A system relying on an alarm and a human response has a response time that is not a design parameter.
Monitoring that shows degradation. Flow at the tool, pressure drop across abatement, scrubber pH and liquid level, all recorded and trended. Almost every abatement failure we are called to investigate was visible in the data for weeks beforehand and was not being looked at.
We design and install ductwork in materials matched to each stream, scrubbers and abatement interfaces, fan systems with redundancy and controls, make-up air, stack arrangements, and the monitoring and interlock systems around them. Permitting for air emissions is a project workstream rather than an afterthought, and it is worth engaging the relevant authority early because it can affect stack location and treatment selection.
Frequently asked questions
Do you install process exhaust and abatement in Oregon?
Yes, across Hillsboro, Portland, Beaverton, Corvallis, Gresham and statewide: segregated ductwork in materials matched to each stream, scrubber and abatement interfaces, fan systems with redundancy, make-up air, stacks, and the monitoring and interlock systems.
Why can’t exhaust streams be combined?
Three reasons, each sufficient alone. Incompatible chemistries react in the duct, with acid and ammonia forming salts that progressively restrict it. Combined streams cannot be treated efficiently because abatement is contaminant-specific. And duct materials suited to one stream are frequently wrong for another.
What determines whether a wet scrubber works?
Contact rather than size. Removal depends on the surface area and time over which gas and liquid interact, so packing condition and liquid and gas distribution matter more than vessel volume. A scrubber with channelled flow does a fraction of its rated work and passes a visual inspection.
How do scrubbers fail quietly?
By running on exhausted liquid. Absorbing acid consumes the scrubbing liquid’s capacity, so pH must be monitored with continuous dosing and bleed. A scrubber whose chemistry is spent removes essentially nothing while looking entirely normal from outside, which makes it the commonest silent abatement failure.
What happens to scrubber blowdown?
It becomes a wastewater stream with its own treatment requirement. Liquid is bled continuously to maintain chemistry, and an abatement project that stops at the stack has moved the problem into the drain rather than solved it. The blowdown treatment belongs in the original scope.
Why does make-up air matter so much?
Because every cubic meter exhausted must be replaced, filtered and conditioned, which is frequently a larger energy cost than the exhaust fans. Adding exhaust capacity without adding make-up inverts the pressure cascade and draws outside air in through whatever gap it can find.
How much redundancy is appropriate?
Enough that loss of a fan does not make a tool room unsafe, which usually means redundant fans with automatic changeover and emergency power on the systems that genuinely require it. This is part of the design case rather than a later upgrade, because retrofitting redundancy into a running fab is expensive.
Should exhaust loss stop the tools?
Yes, automatically and provably. A system relying on an alarm plus a human response has a response time that is not a design parameter and cannot be validated. Interlocks that stop the tools an exhaust branch serves are the control that actually holds.
Where can we save energy safely?
In pressure drop rather than runtime, because exhaust cannot be turned down without consequence. Duct sizing, fitting selection and keeping filters and scrubber packing clean all reduce fan power permanently without compromising safety. At Oregon’s 8.05 cents per kilowatt-hour on a continuous load, that adds up.
How do I get a quote for an Oregon exhaust project?
Use the form on this page or call 201-450-8280. Useful inputs are the tools and chemistries involved, existing stream segregation, current abatement equipment and its condition, available make-up air capacity, and whether air permitting is already in place.
What does a fab do with exhaust that carries both acid and solvent?
It designs the process and the tool so that the two are not generated at the same exhaust point, or it separates them at the tool with dedicated ducts, because a combined stream cannot be treated by a single abatement device and can react in the duct. Where a tool genuinely produces both, point-of-use abatement at the tool handles one before the exhaust joins the other system.
What determines a scrubber's removal efficiency on acid gases?
The contact between gas and liquid, set by packing depth and type, liquid flow rate and gas velocity, together with the liquid's chemistry, which has to keep the absorbed acid in solution. Efficiency falls when any of those drifts, and it is measured rather than assumed.
What instrumentation should a fab scrubber carry?
Recirculation flow, pH and oxidation-reduction potential where chemistry is used, differential pressure across the packing, blowdown flow, and exhaust concentration where a permit requires it, all trended rather than merely alarmed. The trend reveals a scrubber that is degrading long before an alarm does.
How is exhaust duct material selected?
By the stream: fluoropolymer-lined or FRP for acid, stainless for solvent and heat, and coated or specialised materials for specific gases. Duct material that is wrong for the stream corrodes or, in the case of solvent in the wrong duct, becomes a fire path.
What fire protection do solvent exhaust systems need?
Ducts carrying flammable vapour are designed to keep concentrations well below the lower flammable limit, with detection, dampers and often fire suppression in the duct. The design standard follows the fab's insurer and the applicable NFPA requirements.
How should an exhaust system respond when a fan fails?
By starting the standby fan automatically, holding damper positions so that classified spaces do not lose their pressure relationship, and alarming to the fab's control room, with the tool interlocks configured so that a genuine loss of exhaust stops the affected tools safely. The response is designed and tested, not assumed.
Can exhaust heat be recovered in a fab?
General heat exhaust can pass through a heat exchanger to preheat make-up air, and it is one of the larger energy savings available. Acid and solvent streams are not recovered because the exchanger would be exposed to corrosive or flammable air.
What is the difference between an N+1 and a fully duplicated exhaust fan arrangement?
N+1 provides one spare fan beyond the number needed, so that any single fan can fail or be serviced without loss; full duplication provides a complete second set. N+1 is the usual choice for fab exhaust, with the standby fan exercised regularly so that it is known to work.
What is point-of-use abatement, and when is it needed?
Treatment at the tool for gases that must not reach the central exhaust untreated: pyrophoric, toxic or greenhouse gases from etch and deposition. Point-of-use units burn, adsorb or wet-scrub the gas before it joins the house exhaust, and the choice depends on the specific chemistry.
How do you commission a fab exhaust system?
By verifying airflow at every tool connection, static pressure through the system, damper positions, scrubber removal efficiency with stack testing, and interlock function. The balancing report is the document the fab depends on when a tool is added later.
What happens when a new tool is added to a running fab?
Its exhaust demand is added to the stream, the system is rebalanced, make-up air is adjusted and the scrubber loading is checked. Tools added without that review are the usual cause of a fab that certifies at commissioning and drifts out of balance a year later.
How are exhaust systems maintained without stopping production?
With redundancy that allows one fan or one scrubber to be taken offline while others carry the load, and with isolation dampers that let a duct section be worked on. Maintenance access is designed in because the fab cannot stop.
What permits govern fab exhaust in Oregon?
Air quality permits from the Oregon Department of Environmental Quality set emission limits and monitoring requirements, and scrubber performance is demonstrated by testing. Changes to exhaust or abatement can trigger permit modifications, which affects project schedules.
What are the largest avoidable losses in a fab exhaust system?
Over-extraction at tools whose exhaust rates were set conservatively, fans running at full speed against dampers instead of on variable speed drives, and pressure drop across scrubbers and filters that are overdue for maintenance. The energy audit finds them by measuring rather than by estimating.
Do you work on exhaust for smaller advanced manufacturing plants as well as fabs?
Yes. Photonics, semiconductor equipment makers and materials plants in Oregon have smaller versions of the same problem, and the segregation and abatement principles apply at any scale.
Point-of-use abatement and the gases that matter far out of proportion to their volume
There is a category of fab emission where the quantities are small, the concentrations are low, and the environmental significance is enormous, and it is handled quite differently from acid or solvent exhaust.
Several process gases used in semiconductor manufacturing, including fluorinated compounds used for etching and for chamber cleaning, have global warming potentials thousands of times that of carbon dioxide and atmospheric lifetimes measured in thousands of years. A small mass release is a large equivalent emission. That combination makes them a reporting obligation and a corporate target rather than merely a permit line, and it explains why the abatement approach is the opposite of everything else on this page.
Treat at the tool, not at the stack. Everywhere else in a fab exhaust system, consolidating streams before treatment is efficient. For these gases it is the wrong move, because the untreated gas leaving a chamber is concentrated and the same gas after mixing into the general exhaust is not. Destruction efficiency depends strongly on concentration, so treating at the point of use, before dilution, is dramatically more effective and requires far smaller equipment. Point-of-use abatement units sitting directly on the tool exhaust are the norm for exactly this reason.
The destruction methods differ from ordinary abatement. These compounds are chemically stable, which is why their atmospheric lifetimes are so long, and breaking them requires real energy: thermal, plasma or catalytic processes rather than absorption. The abatement unit is an energy-consuming device rather than a passive one, and its own running cost is part of the equation.
The products of destruction need handling. Breaking a fluorinated compound produces acidic products, which then need the wet scrubbing that the rest of this page describes. Abatement units are commonly combined thermal-plus-wet arrangements for that reason, and a plant installing destruction without scrubbing downstream has converted one problem into another.
Efficiency has to be demonstrated, not assumed. Destruction removal efficiency varies with the specific compound, the flow, the concentration and the condition of the unit. A unit that performed to specification at commissioning and has not been verified since is an assumption on a reporting return. Periodic verification, and monitoring that shows the unit is operating in its intended range, is what makes the number defensible.
We design the tool exhaust arrangements, point-of-use abatement interfaces, the downstream scrubbing that handles their products, and the monitoring that lets a plant report on evidence rather than on nameplate.
Exhaust or abatement problems at an Oregon plant?
Tell us which streams are currently combined and when the scrubber chemistry was last verified. Those two answers usually locate the problem. Call 201-450-8280 or use the form below.