A centralized ducted fume extraction system with source capture arms at each station is the best approach for any shop with two or more welding stations. It captures fume at the source, filters it centrally, and returns clean air to the shop. For a 2-station small shop, expect to spend $5,000-12,000 installed. For a 4-6 station mid-size shop, budget $15,000-35,000. The cost is significant, but chronic fume exposure leads to health problems that cost far more in medical bills, lost productivity, and OSHA fines.
Fixed fume extraction systems are permanently installed ventilation that captures and filters welding fume from multiple stations through a shared filter and blower. Unlike portable extractors that serve one station at a time, a ducted system provides simultaneous extraction for every station in the shop.
Types of Fixed Extraction Systems
Source Capture Arms (Ducted)
Articulating extraction arms at each welding station connect to a central duct that leads to a shared filter/blower unit. The arms position 6-12 inches from the arc and capture fume before it disperses. This is the most effective and most common setup for fabrication shops.
Advantages: Highest capture efficiency. Each arm captures at the source. Central filter means one maintenance point. Quiet at the station since the blower is remote.
Disadvantages: Ductwork installation cost. Arms need repositioning with each job. Duct design requires proper engineering to balance airflow across all stations.
Overhead Hoods
Fixed hoods positioned above each welding station capture fume as it rises naturally from the weld. Hoods connect to ductwork and a central blower/filter.
Advantages: Don’t interfere with welding access to the workpiece. No arm to reposition. Work regardless of weld position or workpiece size.
Disadvantages: Lower capture efficiency than source capture arms because the hood is farther from the fume source. Fume passes through the welder’s breathing zone before reaching the hood. Requires higher CFM (1,500-2,500 per station) because of greater capture distance.
Downdraft Tables
Downdraft tables have a perforated or slotted top surface with a plenum underneath connected to a blower and filter. Air is pulled downward through the table surface, carrying fume with it.
Advantages: No arm to position. Works well for cutting, grinding, and welding small parts on the table. The fume is pulled away from the breathing zone immediately.
Disadvantages: Only works for work done on the table surface. Large workpieces that overhang the table aren’t captured. Vertical and overhead welding fume isn’t captured. Table surface must remain unblocked for airflow.
General Dilution Ventilation
Exhaust fans in the roof or walls exchange shop air with outside air, diluting fume concentration. This is the least effective approach and doesn’t meet OSHA requirements in most welding situations.
When it’s used: As a supplement to source capture, not a replacement. In shops where welding is intermittent and exposures are already below PELs. For very large spaces (aircraft hangars, ship hulls) where source capture isn’t practical.
System Sizing Fundamentals
Sizing a fume extraction system correctly requires calculating airflow, filter capacity, and blower specifications. Undersized systems don’t capture enough fume. Oversized systems waste energy and money.
Airflow Per Station
| Capture Method | CFM Per Station | Capture Distance |
|---|---|---|
| Source capture arm | 750-1,000 CFM | 6-12" from arc |
| Overhead hood | 1,500-2,500 CFM | 18-36" above arc |
| Downdraft table | 500-1,000 CFM | Table surface (0-6") |
| General dilution | 2,000-4,000 CFM per station | Room volume exchange |
Total System CFM Calculation
Total CFM = (Number of simultaneous stations) x (CFM per station) x (Duct loss factor)
The duct loss factor accounts for friction in ductwork, bends, transitions, and filters. For straight runs under 50 feet, use 1.2. For longer or complex duct layouts, use 1.3-1.5.
Example: 4 stations with source capture arms, each needing 850 CFM, with moderate duct runs: 4 x 850 x 1.3 = 4,420 CFM total system requirement.
Duct Velocity
ACGIH recommends minimum duct transport velocity of 3,500-4,000 fpm for welding fume. This keeps particulates suspended in the air stream and prevents settling in the ducts. Duct diameter must be sized to maintain this velocity at the design CFM.
| Duct Diameter | CFM at 4,000 fpm |
|---|---|
| 4" | 350 CFM |
| 5" | 545 CFM |
| 6" | 785 CFM |
| 8" | 1,395 CFM |
| 10" | 2,180 CFM |
| 12" | 3,140 CFM |
System Components
Blower (Fan)
The blower generates the airflow and static pressure to move air through the ductwork and filter. It must produce the design CFM at the total system static pressure (sum of duct friction, filter resistance, and hood entry losses).
Centrifugal blowers are standard for welding fume systems. They generate higher static pressure than axial fans, which is necessary to overcome filter and duct resistance. Motor size typically ranges from 1 HP (small 2-station system) to 15+ HP (large multi-station systems).
Filter/Collector
The central filter unit captures particulates from the collected air. Options include:
Cartridge collectors use replaceable filter cartridges (typically nanofiber or cellulose/polyester blend) with self-cleaning pulse-jet systems. Standard for most shop fume extraction. Efficiency: 99.7-99.97% depending on media.
Baghouse collectors use fabric filter bags. More common in large industrial applications. Higher capacity than cartridge collectors but larger footprint.
Wet scrubbers pass fume-laden air through a water spray. Used for specific applications like aluminum dust (which is combustible) and situations where dry filtration creates fire risk.
Ductwork
Welding fume ductwork should be:
- Smooth bore (spiral or smooth-wall, not corrugated flexible duct for main runs)
- Galvanized steel or stainless steel
- Sized for minimum 3,500 fpm transport velocity
- Sloped toward the collector to prevent moisture accumulation
- Equipped with blast gates at each branch for balancing airflow
Flexible duct is acceptable for the final 2-3 feet connecting the extraction arm to the rigid duct. The corrugated interior creates friction, so keep flex duct as short as possible.
Cost Ranges by Shop Size
| Shop Size | Stations | System Type | Installed Cost Range |
|---|---|---|---|
| Home shop | 1 | Portable extractor | $1,200-3,500 |
| Small fab shop | 2-3 | Ducted, source capture | $5,000-15,000 |
| Mid-size fab shop | 4-6 | Ducted, source capture | $15,000-35,000 |
| Large fab shop | 8-12 | Central ducted system | $35,000-75,000 |
| Production facility | 12+ | Engineered system | $75,000-200,000+ |
These ranges include blower, filter unit, ductwork, extraction arms/hoods, installation labor, and electrical connections. They don’t include building modifications (roof penetrations, concrete pads) or permitting costs, which vary by location.
Downdraft Table Options
For shops where welding is primarily done on a fixed table, a downdraft table can serve as both the welding surface and the extraction system.
| Model | Table Size | CFM | Filter Type | Price |
|---|---|---|---|---|
| Miller DownDraft Table | 4' x 4' | 800 CFM | Cartridge, self-cleaning | $4,000-5,500 |
| Lincoln Prism Downdraft | 4' x 6' | 1,000 CFM | Cartridge, self-cleaning | $5,000-7,000 |
| Plymovent DraftMax | 3' x 5' | 750 CFM | Cartridge, self-cleaning | $3,500-5,000 |
Downdraft tables work best when:
- Work stays on the table surface (small parts, fixtures that fit the table)
- Welding and cutting happen in the same area
- The shop lacks ceiling height or wall space for overhead hoods or extraction arms
- A single welding position handles most of the work
ACGIH and OSHA Compliance
The American Conference of Governmental Industrial Hygienists (ACGIH) publishes Industrial Ventilation: A Manual of Recommended Practice, which is the standard reference for welding fume extraction system design. Key ACGIH recommendations:
- Source capture is preferred over general dilution ventilation
- Minimum capture velocity of 100-150 fpm at the hood face
- Minimum duct transport velocity of 3,500-4,000 fpm
- Filter efficiency sufficient to meet clean air return requirements (if air is returned to the shop)
OSHA doesn’t specify exact ventilation equipment requirements but mandates that employee exposure to welding fume constituents stays below Permissible Exposure Limits (PELs). If air monitoring shows PEL exceedances, engineering controls (fume extraction) are required before resorting to respiratory protection.
Getting an industrial hygienist to perform air monitoring in your shop establishes a baseline for compliance. If your current setup meets PELs, document it. If it doesn’t, you have objective data to size the extraction system that will bring you into compliance.
Installation Considerations
Air return vs exhaust. Filtered air can return to the shop or exhaust outside. Return air saves heating/cooling energy but requires high-efficiency filtration (99.97%+). Outdoor exhaust is simpler but creates makeup air requirements (the air you exhaust must be replaced with fresh air, which needs heating or cooling).
Makeup air. For every 1,000 CFM exhausted from the building, 1,000 CFM of makeup air must enter. Without makeup air, the building goes under negative pressure, causing drafts, door-opening problems, and poor extractor performance. In heated shops, the makeup air needs a heater.
Fire suppression. Welding fume extraction systems collecting combustible dust (aluminum, magnesium) require spark arrestors and may require fire suppression (sprinkler or chemical suppression) per NFPA 652 and NFPA 484. Consult your fire marshal and insurance provider.
Permitting. Some jurisdictions require permits for industrial ventilation installations, especially if ductwork penetrates the building envelope or if outdoor exhaust is used. Check local codes before installation.
The Bottom Line
For a single station, buy a portable fume extractor. For 2-3 stations, install a small ducted system with source capture arms and a shared filter unit. For 4+ stations, hire an industrial ventilation engineer to design a proper system.
Don’t try to save money by under-sizing the system. An extraction system that doesn’t capture enough fume is wasted money. Size it right, install it properly, and maintain the filters. Your employees’ health and your OSHA compliance depend on it.
For portable units, see our portable fume extractor guide. For filter selection, check our fume filter types guide. Browse the fume extractors hub for all our ventilation content.
Prices reflect typical street prices at time of writing and are subject to change.